JP7714384B2 - Broadcast area calculation device and program - Google Patents

Description

The present invention relates to a broadcast area calculation device and program that calculates areas where terrestrial digital broadcasting can be received.

Traditionally, the electric field strength at a receiving point for terrestrial digital broadcasting is calculated by combining the direct wave, reflected wave, and diffracted wave. The electrical constants at the reflection point vary depending on whether it is a rice paddy, farmland, or the sea, and the electric field strength of the reflected wave depends on the reflection coefficient, which is determined by the electrical constants at the reflection point. Therefore, the combined electric field of the direct wave and reflected wave at the receiving point varies depending on the land use at the reflection point, and it is necessary to consider not only the distance between the transmitting and receiving points and the height above sea level, but also the land use at the reflection point.

Furthermore, if there is an obstruction such as a high mountain or building between the reflection point and the reception point, reflected waves do not need to be taken into account, but diffracted waves from the obstruction must be taken into account, and the combined wave of direct and diffracted waves will be the electric field strength at the reception point. If the height above sea level of the obstruction is higher than the height above sea level on the line connecting the transmission and reception points, it will be outside the line of sight, and direct waves will not reach the reception point, so it is necessary to calculate the electric field strength at the reception point due to diffracted waves only.

In addition, even when calculating only diffracted waves, the diffraction point must be considered the transmission point, the direct wave and reflected wave must be found again, and the electric field strength at the receiving point must be calculated; this calculation must be performed as many times as diffraction occurs.

As a result, the electric field strength at the receiving point varies depending on the conditions of the propagation path between the transmitting point and the receiving point, so when calculations are made taking into account the above conditions, there is a possibility that the electric field strength will vary significantly even between nearby receiving points.

The Millington method (see, for example, Non-Patent Document 2) described in Ministry of Posts and Telecommunications Notification No. 640 (Non-Patent Document 1) is widely used to calculate such field strength. A method for calculating the service area of medium wave broadcasting using this method has also been reported (see, for example, Non-Patent Document 3).

“Method of Calculating Field Intensity When Determining Broadcasting Areas, etc. Pursuant to the Provisions of Article 7, Paragraph 2 of the Radio Station Licensing Procedure Regulations Based on Calculated Field Intensity,” [online], Ministry of Posts and Telecommunications Notification No. 640, [Retrieved June 15, 2020], Internet <URL: https://www.tele.soumu.go.jp/horei/reiki_honbun/a720730001.html> Rec. ITU-R P.368-9 Annex 2, “GROUND-WAVE PROPAGATION CURVES FOR FREQUENCIES BETWEEN 10 kHz AND 30 MHz”, 2007. Okamoto et al., "Automatic Calculation of Medium Wave Broadcasting Service Areas," 2001 Annual Conference of the Institute of Image Information and Television Engineers, 20-1

However, because actual radio wave propagation has wave-like properties, it can be subject to deflections and complex reflections from buildings and other obstacles along the way. Therefore, in order to accurately determine the received electric field, it is necessary to calculate radio wave propagation taking into account the properties of the waves, in addition to accurate topography and building data, which poses the challenge of taking a very long time to calculate.

Furthermore, even if one attempts to accurately determine the received electric field using this procedure, there is still the issue that the electric field value fluctuates over time due to variations in the refractive index of the air.

Furthermore, in uninhabited areas such as ocean areas, there is no need to accurately determine the electric field value.

The present invention was conceived to solve the above-mentioned problems, and its purpose is to provide a broadcast area calculation device and program that can accurately and quickly calculate areas where terrestrial digital broadcasting can be received.

In order to solve the above problem, the broadcast area calculation device of claim 1 is a broadcast area calculation device that calculates a broadcast area where terrestrial digital broadcasting can be received, and includes a broadcast area calculation unit that calculates the latitude and longitude of a group of area vertices of the broadcast area that satisfy a predetermined required electric field min_se for each target direction hoko, which is obtained by dividing 360 degrees horizontally at predetermined angles based on the transmission point of the broadcast station, as area vertex coordinates area_data[hoko].ido,keido, and the broadcast area calculation unit calculates the maximum distance to the reception point by free space propagation based on the transmission point effective radiated power ERP, which is the effective radiated power of radio waves transmitted from the antenna of the broadcast station, and the required electric field min_se. The system includes a pre-processing unit that calculates kyori2; and a maximum point setting unit that calculates the electric field E for each profile point between the transmission point and the virtual reception point, using the reception point corresponding to the maximum distance kyori2 calculated by the pre-processing unit as a virtual reception point, determines whether the electric field E is equal to or greater than the required electric field min_se for each profile point from the virtual reception point toward the transmission point, and sets the profile point where it is first determined that the electric field E is equal to or greater than the required electric field min_se as a maximum point max_pt, and sets the maximum point max_pt to the area vertex coordinates area_data[hoko].ido,keido.

The broadcast area calculation device of claim 2 is the broadcast area calculation device of claim 1, further comprising a farthest point setting unit that sets the farthest point, wherein the farthest point setting unit calculates a maximum width max1 from the transmission point toward the maximum point max_pt set by the maximum point setting unit at which the electric field E is equal to or greater than the required electric field min_se, sets the profile point closest to the maximum point max_pt at the point of the maximum width max1 to the farthest point max_p, and calculates a distance from the transmission point to the farthest point ma x_p, calculate a maximum width max2 at which the electric field E is less than the required electric field min_se, set the profile point closest to the farthest point max_p at the point of the maximum width max2 as the farthest point min_p, determine whether the maximum width max2 is wider than a predetermined value, and if it is determined that the maximum width max2 is not wider than the predetermined value, set the coordinates of the farthest point max_p as the area vertex coordinates area_data[hoko].ido,keido, and set the maximum width max2 to be wider than the predetermined value. If it is determined that the electric field E is wider than the required electric field min_se, a maximum width max3 from the transmission point toward the farthest point min_p is calculated, the profile point closest to the farthest point min_p at the point of the maximum width max3 is reset to the farthest point max_p, and is set to the area vertex coordinates area_data[hoko].ido,keido. If the electric field E is wider than the required electric field min_se from the farthest point max_p toward the maximum point max_pt, a maximum width max3 is calculated, the electric field E is equal to or greater than the required electric field min_se from the farthest point max_p toward the maximum point max_pt. The method sequentially calculates the width at which the electric field E is equal to or greater than the required electric field min_se, sets the maximum width dspan as the maximum width dspan, and if the width is greater than the set maximum width dspan, updates the maximum width dspan. It also calculates the width A at which the electric field E is equal to or greater than the required electric field min_se, and if the width A exceeds a predetermined multiple of the maximum width dspan, sets the profile point at the point of width A closest to the maximum point max_pt as the area vertex coordinates area_data[hoko].ido,keido.

Furthermore, the broadcast area calculation device of claim 3 is the broadcast area calculation device of claim 1 or 2, further comprising a broadcast area correction unit that averages the positions of a predetermined number of adjacent area vertex coordinates area_data[hoko].ido,keido for each target direction hoko calculated by the broadcast area calculation unit.

Furthermore, the broadcast area calculation device of claim 4 is the broadcast area calculation device of any one of claims 1 to 3, wherein the maximum point setting unit calculates an average value for each profile point between the transmission point and the maximum point max_pt based on the electric field E of a plurality of consecutive profile points including the profile point, and sets the average value as the electric field E of the profile point.

Furthermore, the broadcast area calculation device of claim 5 is the broadcast area calculation device of any one of claims 1 to 4, characterized in that the maximum point setting unit calculates antenna directivity ant_loss for each predetermined angle j in the vertical direction of the broadcast station's antenna, sets the antenna directivity ant_loss at which the antenna gain is maximized as antenna directivity a_loss, calculates maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss, uses maximum distance kyori instead of maximum distance kyori2, sets the reception point corresponding to maximum distance kyori as the virtual reception point, and sets the maximum point max_pt.

Furthermore, the broadcast area calculation device of claim 6 is characterized in that, in the broadcast area calculation device of claim 3, it further comprises a land use data storage unit that stores land use data for each mesh of a predetermined size, and the broadcast area correction unit reads out the land use data at the position of the averaged area vertex coordinates area_data[hoko].ido,keido from the land use data storage unit, and if the land use data is a sea area, moves the position of the averaged area vertex coordinates area_data[hoko].ido,keido toward the transmission point so that the area vertex indicated by the averaged area vertex coordinates area_data[hoko].ido,keido does not fall within the mesh of the sea area.

Furthermore, the broadcast area calculation device of claim 7 is the broadcast area calculation device of any one of claims 1 to 5, further comprising a land use data storage unit that stores land use data for each mesh of a predetermined size, and the maximum point setting unit reads the land use data of the profile point between the transmission point and the virtual reception point from the land use data storage unit, determines whether the land use data of the profile point is a sea area, and calculates the electric field E for the profile point when the land use data is not a sea area.

Furthermore, the program of claim 8 includes a computer constituting a broadcast area calculation device that calculates the latitude and longitude of a group of area vertices of a broadcast area that satisfies a predetermined required electric field min_se for each target direction hoko obtained by dividing 360 degrees horizontally at predetermined angles based on the broadcast station's transmission point, as area vertex coordinates area_data[hoko].ido,keido, and includes a preprocessing unit that calculates the maximum distance kyori2 of a receiving point due to free space propagation based on the transmitting point effective radiated power ERP, which is the effective radiated power of radio waves transmitted from the broadcast station's antenna, and the required electric field min_se, and a processing unit that calculates the maximum distance kyori2 of a receiving point due to free space propagation based on the transmitting point effective radiated power ERP, which is the effective radiated power of radio waves transmitted from the broadcast station's antenna, and the required electric field min_se. The reception point corresponding to the calculated maximum distance kyori2 is set as a virtual reception point, and the electric field E for each profile point between the transmission point and the virtual reception point is calculated. From the virtual reception point toward the transmission point, it is determined for each profile point whether the electric field E is equal to or greater than the required electric field min_se. The profile point at which it is first determined that the electric field E is equal to or greater than the required electric field min_se is made to function as a maximum point setting unit that sets the maximum point max_pt, and the maximum point max_pt is set to the area vertex coordinates area_data[hoko].ido,keido.

As described above, the present invention makes it possible to accurately and quickly calculate areas where terrestrial digital broadcasting can be received.

1 is a block diagram showing an example of the configuration of a broadcast area calculation device according to a first embodiment; 10 is a flowchart illustrating an example of processing by a broadcast area calculation device. 10 is a block diagram showing an example of the configuration of a broadcast area calculation unit. FIG. 10 is a flowchart showing an example of processing (step S202) by a broadcast area calculation unit. 10 is a flowchart illustrating an example of preprocessing (step S402). 10 is a flowchart showing an example of a target direction setting process (step S403); Process 1: A flowchart showing an example of maximum point setting process (step S404) from a distant location toward a transmission point. 10 is a flowchart illustrating an example of a process 1a. 10 is a flowchart illustrating an example of process 1b. 10 is a flowchart illustrating an example of process 1c. 10 is a flowchart illustrating an example of a process 1d. Process 2: A flowchart showing an example of a process for setting the farthest point from the transmission point toward a distant location (step S405). 10 is a flowchart illustrating an example of a process 2a. 10 is a flowchart illustrating an example of a process 2b. 10 is a flowchart illustrating an example of process 2c. 10 is a flowchart illustrating an example of a process 2d. 16 is a flowchart showing details (1) of steps S1602 to S1608 of process 2d. 10 is a flowchart showing details (2) of steps S1602 to S1608 of process 2d. 10 is a flowchart showing an example of processing (step S203) of the broadcast area correction unit 19. 10A and 10B are diagrams illustrating an example of a target direction hoko setting process (step S601). FIG. 10 is a diagram illustrating an example of process 1a. FIG. 10 is a diagram illustrating an example of process 1b. FIG. 10 is a diagram illustrating an example of process 1c. FIG. 10 is a diagram illustrating an example of process 1d. FIG. 10 is a diagram illustrating an example of process 2a. FIG. 10 is a diagram illustrating an example of process 2b. FIG. 10 is a diagram illustrating an example of process 2c. FIG. 10 is a diagram illustrating an example of process 2d. FIG. 10 is a block diagram illustrating a configuration example of a broadcast area calculation device according to a second embodiment. 11 is a flowchart illustrating an example of processing (corresponding to step S203) of a broadcast area correction unit in the second embodiment. FIG. 11 is a block diagram illustrating a configuration example of a broadcast area calculation device according to a third embodiment.

The following describes in detail the embodiments of the present invention with reference to the accompanying drawings. Hereinafter, the term "broadcast area" refers to the range where radio waves emitted from a terrestrial digital broadcasting transmission point reach a receiving point capable of receiving terrestrial digital broadcasting, and where the electric field strength (hereinafter referred to as "electric field") at the receiving point satisfies predetermined conditions based on the required electric field.

Example 1
First, a broadcast area calculation device according to Example 1 will be described. The broadcast area calculation device according to Example 1 calculates the electric field E for each profile point by determining a virtual reception point that takes into account free space propagation loss and antenna gain for each target direction of 360 degrees horizontally with the transmission point as the reference, sets a maximum point max_pt in processing from a distance toward the transmission point, sets the farthest points max_p and min_p in processing from the transmission point toward a distance, and calculates the broadcast area by comparing the electric field E with the required electric field min_se. According to Example 1, the broadcast area can be calculated accurately and quickly.

Figure 1 is a block diagram showing an example of the configuration of a broadcast area calculation device according to the first embodiment, and Figure 2 is a flowchart showing an example of processing by the broadcast area calculation device. This broadcast area calculation device 1-1 includes a required electric field input unit 10, a constant memory unit 11, a transmission point information memory unit 12, a topographical height data memory unit 13, a land reflection coefficient memory unit 14, a land use data memory unit 15, a land reflection coefficient calculation unit 16, a broadcast area calculation unit 17, a broadcast area information memory unit 18, a broadcast area correction unit 19, and a broadcast area drawing unit 20.

The required electric field input unit 10 has the function of inputting two required electric fields syoyou_e and syoyou_e2, which serve as the basis for calculating the broadcast area, in accordance with user operation, and the function of inputting an instruction to start the process of calculating the broadcast area. The required electric field input unit 10 outputs the required electric fields syoyou_e and syoyou_e2 input in accordance with user operation and the start instruction to the broadcast area calculation unit 17. Here, the required electric field input unit 10 is configured to input the two required electric fields syoyou_e and syoyou_e2, but it is sufficient if at least one of the two required electric fields syoyou_e and syoyou_e2 can be input.

The constant memory unit 11 stores a constant for the number of angular steps hoko_step. The number of angular steps hoko_step indicates the angular unit used to determine the direction in which the broadcast area is calculated over one rotation of 360 degrees based on the transmission point. For example, an angular step number hoko_step = 2 degrees is used, in which case the broadcast area is calculated for each 2-degree direction in 360 degrees. The number of angular steps hoko_step is set in advance by the user or stored externally.

The transmission point information storage unit 12 stores transmission point information such as the latitude and longitude of the broadcast station (hereinafter referred to as the "transmission point") being calculated, the antenna height (transmission point height send_h), the antenna gain, and the transmission point effective radiated power ERP. The transmission point information is set in advance by the user or stored by external means. The transmission point effective radiated power ERP is the effective power of the radio waves transmitted from the broadcast station's antenna.

The terrain height data storage unit 13 stores the heights of the terrain (terrain height data) divided into meshes of a predetermined size (for example, 5 m square, 10 m square, 50 m square). The terrain height data for each mesh of a predetermined size is set in advance by the user or stored by external means.

The land reflection coefficient memory unit 14 stores the land reflection coefficient for each mesh of a predetermined size calculated by the land reflection coefficient calculation unit 16. The land reflection coefficient is used when calculating the reflected wave when calculating the electric field E at a profile point in the broadcast area calculation process.

The land use data storage unit 15 stores land use data for each mesh of a predetermined size. The land use data is classified into, for example, marine areas, terraces, high-relief mountainous areas, etc.

The land reflection coefficient calculation unit 16 reads land use data for each mesh of a predetermined size from the land use data storage unit 15. The land reflection coefficient calculation unit 16 then calculates a land reflection coefficient based on the land use data and stores the land reflection coefficient for each mesh of the predetermined size in the land reflection coefficient storage unit 14.

For example, the land reflection coefficient calculation unit 16 has a table (a pre-set table) that defines the relationship between land use data and land reflection coefficients. The land reflection coefficient calculation unit 16 reads land use data from the land use data storage unit 15 for each mesh of a predetermined size, reads the land reflection coefficient corresponding to the land use data from the table, and stores this in the land reflection coefficient storage unit 14.

The broadcast area calculation unit 17 inputs the required electric fields syoyou_e and syoyou_e2 and a start command from the required electric field input unit 10. The broadcast area calculation unit 17 also reads the number of angular steps hoko_step (=2) from the constant memory unit 11, transmission point information from the transmission point information memory unit 12, and terrain height data for each mesh of a predetermined size from the terrain height data memory unit 13. The broadcast area calculation unit 17 also reads the land reflection coefficient for each mesh of a predetermined size from the land reflection coefficient memory unit 14.

When a start command is input from the required electric field input unit 10 (step S201), the broadcast area calculation unit 17 starts the broadcast area calculation process (step S202).

In other words, the broadcast area calculation unit 17 calculates the electric field E in the horizontal 360-degree direction based on the transmission point using the required electric field syoyou_e, syoyou_e2, the number of angular steps hoko_step, transmission point information, terrain height data for each mesh of a predetermined size, and land reflection coefficients, etc., to calculate the broadcast area in which the electric field E at the receiving point satisfies the required electric field min_se.

The broadcast area is composed of a group of area vertices connecting the farthest points where the electric field E satisfies the required electric field min_se in each horizontal direction of 360 degrees from the transmission point, and is represented by the area vertex coordinates area_data[hoko].ido,keido, which are the latitude and longitude of the group of area vertices.

The broadcast area calculation unit 17 stores the area vertex coordinates area_data[hoko].ido,keido as broadcast area information in the broadcast area information storage unit 18.

The broadcast area information storage unit 18 stores the latitude and longitude of the area vertices that define the broadcast area as area vertex coordinates area_data[hoko].ido,keido for each target direction hoko, which is obtained by dividing the horizontal 360 degrees from the transmission point by the number of angular steps hoko_step.

The broadcast area correction unit 19 reads the area vertex coordinates area_data[hoko].ido,keido, which are broadcast area information, from the broadcast area information storage unit 18. Then, the broadcast area correction unit 19 performs corrections such as eliminating protruding and notched area vertices so that the shape (broadcast area shape) formed by connecting the area vertex coordinates area_data[hoko].ido,keido of the area vertex group is smooth (step S203). For example, the broadcast area correction unit 19 compares multiple adjacent area vertex coordinates area_data[hoko].ido,keido, detects the positions of protruding area vertex coordinates area_data[hoko].ido,keido, and averages them.

The broadcast area correction unit 19 outputs the corrected area vertex coordinates area_data[hoko].ido,keido to the broadcast area drawing unit 20. The corrected area vertex coordinates area_data[hoko].ido,keido are treated as a group of vertices for drawing the broadcast area by the broadcast area drawing unit 20. Details of the processing by the broadcast area correction unit 19 will be described later.

The broadcast area drawing unit 20 receives the corrected area vertex coordinates area_data[hoko].ido,keido from the broadcast area correction unit 19. The broadcast area drawing unit 20 then generates a display signal for drawing the broadcast area on a map based on the corrected area vertex coordinates area_data[hoko].ido,keido, and outputs the display signal to the display device 2 (step S204).

In addition, the broadcast area drawing unit 20 may input the drawing color from the required electric field input unit 10, generate a display signal for drawing the broadcast area on a map using that drawing color, and output it to the display device 2.

[Broadcast area calculation unit 17]
Next, a detailed description will be given of the broadcast area calculation unit 17 shown in Fig. 1. Fig. 3 is a block diagram showing an example of the configuration of the broadcast area calculation unit 17, and Fig. 4 is a flowchart showing an example of processing (step S202) of the broadcast area calculation unit 17.

The broadcast area calculation unit 17 includes a preprocessing unit 30, a maximum point setting unit 31, and a farthest point setting unit 32.

The broadcast area calculation unit 17 inputs the required electric fields syoyou_e and syoyou_e2 and a start command from the required electric field input unit 10, and begins the broadcast area calculation process at the timing when the start command is input. The broadcast area calculation unit 17 then inputs the number of angular steps hoko_step from the constant memory unit 11 and transmission point information from the transmission point information memory unit 12. When calculating the electric field E at the reception point, the broadcast area calculation unit 17 reads the terrain height data and land reflection coefficient for each mesh of a predetermined size from the terrain height data memory unit 13 and the land reflection coefficient memory unit 14, respectively (step S401).

As preparatory processing before calculating the electric field E in all directions from 0 to 360 degrees relative to the transmission point, the preprocessing unit 30 performs preprocessing such as setting the required electric field min_se and setting the maximum distance kyori2 to the reception point due to free space propagation (step S402). Details of the preprocessing performed by the preprocessing unit 30 will be described later.

The maximum point setting unit 31 performs a process of setting target directions, etc., for which the broadcast area is to be calculated (step S403). The target direction, etc., setting process performed by the maximum point setting unit 31 will be described in detail later. The processes of steps S404 and S405, which will be described later, are performed for each set target direction, etc.

The maximum point setting unit 31 performs processing (processes 1a, 1b, 1c, and 1d) such as setting a maximum point max_pt based on a comparison of the electric field E of the reception point and the required electric field min_se from the distant location where the virtual reception point is set toward the transmission point (step S404). Details of the maximum point setting processing performed by the maximum point setting unit 31 from the distant location toward the transmission point will be described later.

The maximum point max_pt is the profile point closest to the virtual reception point among the reception points that satisfy the required electric field min_se, taking into account the effects of diffracted waves, reflected waves, etc.

The farthest point setting unit 32 sets the farthest points max_p and min_p from the transmission point to the distant location where the virtual reception point is set based on the maximum widths max1 and max2 derived by comparing the electric field E of the reception point and the required electric field min_se, and performs processes such as calculating the area vertex coordinates area_data[hoko].ido and keido (processes 2a, 2b, 2c, and 2d) (step S405).

The farthest point max_p is the profile point closest to the virtual reception point among the reception points of maximum width max1 where the electric field E is equal to or greater than the required electric field min_se on the straight line from the transmission point to the virtual reception point. Furthermore, the farthest point min_p is the profile point closest to the virtual reception point among the reception points of maximum width max2 where the electric field E is less than the required electric field min_se on the straight line from the transmission point to the virtual reception point.

The farthest point setting unit 32 determines whether processing of all target direction hokos has been completed (step S406). If the farthest point setting unit 32 determines in step S406 that processing of all target direction hokos has not been completed (step S406: N), it proceeds to step S403. As a result, a new target direction hoko is set, and the processing of steps S403 to S405 is performed.

On the other hand, if the farthest point setting unit 32 determines in step S406 that processing for all target directions hoko has been completed (step S406: Y), it stores the area vertex coordinates area_data[hoko].ido,keido of all target directions hoko as broadcast area information in the broadcast area information storage unit 18 (step S407). Details of the farthest point setting process from the transmission point to a distant location by the farthest point setting unit 32 will be described later.

(Pretreatment)
Next, a detailed description will be given of the pre-processing in step S402 by the pre-processing unit 30 shown in Fig. 4. Fig. 5 is a flowchart showing an example of the pre-processing (step S402).

The pre-processing unit 30 reads the number of angular steps hoko_step (e.g., 2 degrees) from the constant storage unit 11 and sets the number of angular steps hoko_step to be used in the processing described below (step S501).

The angular step number hoko_step is an angle used to discretely select 360 degrees horizontally with the transmission point at the center. Here, the farther the vertices of the broadcast area are from the transmission point, the greater the distance between adjacent vertices due to a horizontal angle difference of 1 degree. For this reason, the angular step number hoko_step should be set to as small an angle as possible, but the smaller the angular step number hoko_step, the greater the number of calculations required. Therefore, as a result of past experience, the broadcast area can be calculated with sufficient accuracy by setting the angular step number hoko_step to 2 degrees, for example.

The preprocessing unit 30 reads the transmission point information from the transmission point information storage unit 12 and, based on the transmission point effective radiated power ERP included in the transmission point information, sets the distance direction step number stp so that the smaller the transmission point effective radiated power ERP, the smaller the value of the distance direction step number stp, and the larger the transmission point effective radiated power ERP, the larger the value of the distance direction step number stp (step S502).

For example, if the transmission point effective radiated power ERP is less than 1 W, the preprocessing unit 30 sets the distance direction step number stp to 2; if the transmission point effective radiated power ERP is 1 W or greater but less than 10 W, the preprocessing unit 30 sets the distance direction step number stp to 3. If the transmission point effective radiated power ERP is 10 W or greater but less than 100 W, the preprocessing unit 30 sets the distance direction step number stp to 4; if the transmission point effective radiated power ERP is 100 W or greater but less than 1000 W, the preprocessing unit 30 sets the distance direction step number stp to 5. If the transmission point effective radiated power ERP is 1000 W or greater but less than 10,000 W, the preprocessing unit 30 sets the distance direction step number stp to 6; and if the transmission point effective radiated power ERP is 10,000 W or greater, the preprocessing unit 30 sets the distance direction step number stp to 7.

As a result, the smaller the transmission point effective radiated power ERP, the smaller the distance direction step number stp is set, and the larger the transmission point effective radiated power ERP, the larger the distance direction step number stp is set. This distance direction step number stp is used in process 1d, which will be described later.

Here, if the transmitting point effective radiated power ERP is large, the broadcast area will extend farther, and the maximum point max_pt and virtual reception point calculated along the way will also be farther away. Specifically, in process 1d, described below, the larger the transmitting point effective radiated power ERP, the more profile points there are to be processed. This increases the number of processes for setting the electric field E = 0 for each profile point and averaging the electric field E, resulting in a higher processing load.

Therefore, the number of processing steps is changed depending on the magnitude of the transmission point effective radiated power ERP. Specifically, when the transmission point effective radiated power ERP is large, the preprocessing unit 30 sets a large value for the number of distance-direction steps stp, thereby reducing the number of processing steps for process 1d, which will be described later. Therefore, when the transmission point effective radiated power ERP is large, the processing load for process 1d, which will be described later, can be reduced, and higher speeds can be achieved.

The pre-processing unit 30 inputs the two required electric fields syoyou_e and syoyou_e2 from the required electric field input unit 10 and sets the required electric field min_se to the lower of the required electric fields syoyou_e and syoyou_e2 (step S503). Note that the pre-processing unit 30 may also input the required electric field min_se directly from the required electric field input unit 10.

The preprocessing unit 30 calculates the maximum distance kyori2, which is the farthest distance taking into account free space loss, using the following equation based on the transmission point effective radiated power ERP and the required electric field min_se (step S504).
[Equation 1]
kyori2 = (7√ERP/10 ^{(min_se-60)/20} ) × 1000 [m] ... (1)

If the maximum distance kyori2 calculated in step S504 exceeds 1000 km, the preprocessing unit 30 clips kyori2 to 1000 km.

(Target direction setting process)
Next, a detailed description will be given of the target direction setting process in step S403 by the maximum point setting unit 31 shown in Fig. 4. Fig. 6 is a flowchart showing an example of the target direction setting process (step S403).

The maximum point setting unit 31 sets the target direction hoko to be used to calculate the broadcast area using the following formula based on the number of angular direction steps hoko_step (e.g., 2 degrees) set by the pre-processing unit 30 (step S601).
[Equation 2]
hoko=hoko_step×k [degrees] ...(2)
Here, the parameter k=0, 1, . . . , 179.

Figure 20 is a diagram illustrating an example of the target direction hoko setting process (step S601). As shown in Figure 20, in the horizontal 360-degree direction based on the transmission point, target directions hoko = 0, 2, ..., 358 [degrees] corresponding to k = 0, 1, ..., 179 are set. In addition, the coordinates of the virtual reception point are calculated in step S602, which will be described later.

Returning to Figure 6, the maximum point setting unit 31 sets the point corresponding to the maximum distance kyori2 of the target direction hoko relative to the transmission point as the virtual reception point. The maximum point setting unit 31 calculates the virtual reception point coordinates (latitude and longitude of the virtual reception point) based on the maximum distance kyori2, the target direction hoko, and the latitude and longitude of the transmission point included in the transmission point information (step S602). This allows the virtual reception point coordinates to be calculated for each target direction hoko.

(Process 1: Maximum point setting process from a distance toward the transmission point)
Next, a detailed description will be given of the process 1 of step S404 by the maximum point setting unit 31 shown in Fig. 4: the maximum point setting process from a distant location toward the transmission point. Fig. 7 is a flowchart showing an example of the process 1: the maximum point setting process from a distant location toward the transmission point (step S404).

The maximum point setting unit 31 calculates the antenna directivity for each vertical angle by changing the vertical angle of the antenna at the transmission point. The maximum point setting unit 31 then identifies the maximum antenna directivity (the antenna directivity that maximizes antenna gain (minimizes loss)) and calculates the maximum distance kyori based on the maximum antenna directivity (step S701, process 1a).

The maximum point setting unit 31 calculates the virtual reception point coordinates corresponding to the maximum distance kyori, and calculates the electric field E, the number of profile points p_count, and the number of steps p_step for each profile point (step S702, process 1b).

The maximum point setting unit 31 identifies the electric field E at the specified point for each step number p_step from the electric field E at each profile point from the distant virtual reception point toward the transmission point. Then, the maximum point setting unit 31 sets the maximum point max_pt by comparing the electric field E at the specified point with the required electric field min_se (step S703, process 1c).

The maximum point setting unit 31 averages the electric field E for a predetermined number of consecutive profile points between the transmission point and the maximum point max_pt, and sets the electric field E between the profile points after the maximum point max_pt and the virtual reception point to 0 (step S704, process 1d).

(Process 1a)
Next, a detailed description will be given of process 1a (calculating the maximum distance kyori based on the antenna directivity) in step S701 shown in Fig. 7. Fig. 8 is a flowchart showing an example of process 1a, and Fig. 21 is a diagram explaining an example of process 1a.

As mentioned above, process 1a calculates the antenna directivity for each vertical angle of the transmitting antenna, identifies the antenna directivity that maximizes antenna gain (minimizes loss), and calculates the maximum distance kyori based on the maximum antenna directivity.

The maximum point setting unit 31 sets the height of the virtual reception point to be equal to the transmission point height send_h, which is the height of the transmission point, and initializes the antenna directivity a_loss (setting the antenna directivity a_loss to the minimum possible value) (step S801).

The maximum point setting unit 31 sets the vertical angle j for the antenna at the transmission point (step S802). The angle j is set to 0, 2, ..., 10, and the angle j is set in order each time the process moves from step S801 and step S806 (described later).

The maximum point setting unit 31 calculates the virtual reception point height for calculation recv_h based on the transmission point height send_h, the maximum distance kyori2, and the angle j using the following formula (step S803).
[Equation 3]
recv_h=send_h-floor{kyori2×tan(jπ/180)×10}...(3)
floor indicates the floor function.

The maximum point setting unit 31 calculates the antenna directivity ant_loss(recv_h) based on the virtual reception point height for calculation recv_h (step S804). Specifically, the antenna directivity ant_loss(recv_h) is calculated based on reception point information such as the virtual reception point height for calculation recv_h, with the position (latitude and longitude) of the transmission point and the transmission point height send_h being known.

The maximum point setting unit 31 determines whether the antenna directivity a_loss is smaller than the antenna directivity ant_loss(recv_h) (a_loss < ant_loss(recv_h)), and if a_loss < ant_loss(recv_h), sets the antenna directivity ant_loss(recv_h) to the antenna directivity a_loss (step S805). In other words, the maximum point setting unit 31 sets the maximum value of the antenna directivity ant_loss(recv_h) to the antenna directivity a_loss. Note that here, the maximum point setting unit 31 calculates the virtual reception point height for calculation recv_h and calculates the antenna directivity ant_loss based on the virtual reception point height for calculation recv_h. However, because data measuring the gain characteristics in the angular direction exists for the antenna during the manufacturing stage, the maximum point setting unit 31 does not need to calculate the virtual reception point height for calculation recv_h.

In the initial processing, the antenna directivity a_loss is initialized to a value with a large loss. Therefore, the maximum point setting unit 31 determines that a_loss < ant_loss(recv_h) and sets the antenna directivity ant_loss(recv_h) as the antenna directivity a_loss.

The maximum point setting unit 31 determines whether processing for all angles j has been completed (step S806). If the maximum point setting unit 31 determines in step S806 that processing for all angles j has not been completed (step S806: N), it proceeds to step S802. The maximum point setting unit 31 then performs the processing of steps S802 to S805 for the next angle j.

Then, if the maximum point setting unit 31 determines in step S806 that processing of all angles j has been completed (step S806: Y), it calculates the maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss using the following formula (step S807).
[Equation 4]
kyori = kyori2 × 10 ^a_loss/20 ... (4)

In this way, in process 1a, the maximum point setting unit 31 calculates the antenna directivity ant_loss(recv_h) for each vertical angle j of the antenna at the transmission point, sets the maximum antenna directivity ant_loss(recv_h) as the antenna directivity a_loss, and calculates the maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss. Here, the maximum antenna directivity ant_loss(recv_h) means that the antenna gain is maximum (minimum loss), i.e., the radio waves can be transmitted further. This allows for the maximum distance kyori to be obtained, taking into account the minimum loss due to antenna directivity.

Generally, antenna directivity ant_loss (recv_h) is greatest in the direction of the antenna's central axis (horizontal to the ground (0 degrees)), but depending on the installation environment of the transmitting point, the transmitting antenna may not necessarily be installed in the direction of the antenna's central axis. For this reason, a shift in the angle in the vertical direction will change the antenna gain.

The maximum distance kyori2 assumes that the height of the transmitting point (transmitting point height send_h) and the height of the virtual receiving point are the same, so this is the distance when the antenna gain is maximum. To calculate the maximum distance kyori, the antenna directivity ant_loss (recv_h) is obtained by lowering the height of the virtual receiving point, and the minimum loss of the antenna directivity ant_loss (recv_h) for the height of the virtual receiving point corresponding to the vertical angle deviation of the transmitting antenna is taken as the antenna directivity a_loss.

(Process 1b)
Next, a detailed description will be given of process 1b: calculation of the electric field E, the number of profile points p_count, and the number of steps p_step for each profile point in step S702 shown in Fig. 7. Fig. 9 is a flowchart showing an example of process 1b, and Fig. 22 is a diagram explaining an example of process 1b.

As mentioned above, process 1b calculates the virtual reception point coordinates corresponding to the maximum distance kyori, and calculates the electric field E, the number of profile points p_count, and the number of steps p_step for each profile point between the transmission point and the virtual reception point.

The maximum point setting unit 31 calculates the virtual reception point coordinates based on the maximum distance kyori, the target direction hoko, and the latitude and longitude of the transmission point included in the transmission point information (step S901).

The maximum point setting unit 31 reads the terrain height data for the virtual reception point coordinates (for each mesh of the mesh size used) from the terrain height data storage unit 13 and identifies the terrain height (mesh height) of the virtual reception point coordinates. The maximum point setting unit 31 then adds a preset increment (the height from the ground to the antenna installed on the house) to the mesh height and sets the result of the addition as the height of the virtual reception point (step S902).

The maximum point setting unit 31 performs profile calculations to calculate the electric field E for each profile point between the transmission point and the virtual reception point, as shown in the lower diagram of Figure 22 (step S903).

Specifically, the maximum point setting unit 31 calculates the electric field E for each profile point between the transmission point and the virtual reception point based on the virtual reception point coordinates, the height of the virtual reception point, the transmission point information read from the transmission point information storage unit 12, the terrain height data for the transmission point, reflection point, and reception point read from the terrain height data storage unit 13, and the land reflection coefficients for the transmission point, reflection point, and reception point read from the land reflection coefficient storage unit 14.

Note that the profile calculation method for calculating the electric field E is well known, so a detailed explanation will be omitted here.

The maximum point setting unit 31 calculates the profile score p_count based on the mesh size used and the distance between the transmission point and the virtual reception point (maximum distance kyori) (step S904).

The maximum point setting unit 31 calculates the number of steps p_step based on the profile score p_count using the following formula (step S905).
[Equation 5]
p_step=floor(p_count/10)...(5)

Note that in equation (5), the maximum point setting unit 31 divides the profile score p_count by 10, but 10 is an example and any positive integer will do.

For example, referring to the bottom diagram in Figure 22, the profile score p_count = 1000 and the step count p_step = floor(1000/10) = 100 are obtained.

The maximum point setting unit 31 corrects the number of steps p_step calculated in step S905 according to the mesh size used (step S906).

Specifically, if the number of steps p_step is greater than the number corresponding to the mesh size being used, the maximum point setting unit 31 sets the number of steps p_step to the number corresponding to the mesh size being used. For example, if the mesh size being used is 10 m square and the number of steps p_step is greater than 300, the number of steps p_step is set to 300. Also, if the mesh size being used is 50 m square and the number of steps p_step is greater than 60, the number of steps p_step is set to 60.

In this way, in process 1b, the maximum point setting unit 31 calculates the virtual reception point coordinates corresponding to the maximum distance kyori, calculates the electric field E, the number of profile points p_count, and the number of steps p_step for each profile point between the transmission point and the virtual reception point, and corrects the number of steps p_step.

Here, in profile calculations, the number of profile points p_count varies depending on the mesh size used; if the mesh size is small, the number of profile points p_count increases, and the number of steps p_step also increases.

Therefore, in step S906, the maximum point setting unit 31 corrects the number of steps p_step according to the mesh size used so that it does not become larger than necessary. As a result, the number of steps p_step does not become large, so calculations do not become coarse and calculation accuracy can be ensured.

Furthermore, in processes such as process 1c described below, instead of processing each profile score p_count (e.g., 1000 points), processing is performed at intervals of the step number p_step (100 points) of the profile score p_count. In other words, 1000 processes can be reduced to 10 processes, achieving approximately 1/100 the processing load and approximately 100 times the processing speed. The step number p_step is used to reduce the processing load and speed up processing.

(Process 1c)
Next, a detailed description will be given of process 1c (maximum point max_pt setting process) in step S703 shown in Fig. 7. Fig. 10 is a flowchart showing an example of process 1c, and Fig. 23 is a diagram explaining an example of process 1c.

As mentioned above, process 1c is a process that identifies the electric field E at a specified point for each step number p_step from the electric field E at each profile point from a distant virtual reception point toward the transmission point, and sets the maximum point max_pt by comparing the electric field E at the specified point with the required electric field min_se.

The maximum point setting unit 31 sets designated points for each profile point spaced at intervals of the step number p_step from the distant virtual reception point toward the transmission point (step S1001). The designated points are set from the virtual reception point toward the transmission point when processing 1c starts and each time processing transitions from step S1003, described below.

The maximum point setting unit 31 identifies the electric field E at the specified point from the electric field E at each profile point (step S1002).

The maximum point setting unit 31 determines whether the electric field E at the specified point is equal to or greater than the required electric field min_se (step S1003). If the maximum point setting unit 31 determines in step S1003 that the electric field E at the specified point is not equal to or greater than the required electric field min_se (step S1003: N), it proceeds to step S1001. Then, the maximum point setting unit 31 sets the next specified point at an interval of the number of steps p_step toward the transmission point, and performs the processing of steps S1001 and S1002.

On the other hand, if the maximum point setting unit 31 determines in step S1003 that the electric field E at the specified point is equal to or greater than the required electric field min_se (step S1003: Y), it identifies the specified point from the virtual reception point toward the transmission point where the electric field E is first equal to or greater than the required electric field min_se. The maximum point setting unit 31 then adds the number of steps p_step to the specified point (step S1004). The maximum point setting unit 31 then sets the profile point resulting from the addition as the maximum point max_pt (step S1005).

The reason why a specified point where the electric field E is determined to be equal to or greater than the required electric field min_se is not set as the maximum point max_pt is because it takes into account the possibility that a profile point with an electric field E equal to or greater than the required electric field min_se may be included between the specified point and the profile point obtained by adding the number of steps p_step to the specified point (the point located back by the number of steps p_step toward the virtual reception point).

For example, referring to the lower diagram in Figure 23, assume that the electric field E at the designated point of profile point 500 is determined to be equal to or greater than the required electric field min_se = 60. In this case, the maximum point max_pt is set to a profile point obtained by adding the number of steps p_step = 100 to the designated point of profile point 500 (the designated point of profile point 600). This is because it takes into account the possibility that there may be a profile point between the designated points of profile point 500 and profile point 600 where the electric field E is equal to or greater than the required electric field min_se. Note that in Figure 23, there are no profile points between the designated points of profile point 500 and profile point 600 where the electric field E is equal to or greater than the required electric field min_se.

Returning to FIG. 10, the maximum point setting unit 31 corrects the maximum point max_pt set in step S1005 in accordance with the transmission point effective radiated power ERP (step S1006). As a result, the maximum point max_pt is set to a position that is at least the distance (the radio wave reach) that is preset in accordance with the transmission point effective radiated power ERP.

Specifically, the maximum point setting unit 31 determines whether the distance corresponding to the maximum point max_pt set in step S1005 (the distance from the transmission point to the maximum point max_pt) is shorter than a distance preset according to the transmission point effective radiated power ERP (the maximum distance that radio waves can reach). If the maximum point setting unit 31 determines that the distance corresponding to the maximum point max_pt is shorter than the preset distance, it corrects the maximum point max_pt to the profile point corresponding to that distance.

For example, if the mesh size used is 10m square and the transmission point effective radiated power ERP is greater than 100W, and the maximum point max_pt set in step S1005 is less than or equal to 1000, the maximum point max_pt is set to 1000. This is because, when the transmission point effective radiated power ERP is greater than 100W, it is assumed that radio waves can reach a distance of 10km or more from the transmission point, and 1000 x 10 = 10km is set as the distance corresponding to the maximum point max_pt.

Furthermore, if the mesh size used is 10m square and the transmission point effective radiated power ERP is 100W or less, and the maximum point max_pt set in step S1005 is 300 or less, the maximum point max_pt is set to 300. This is because, when the transmission point effective radiated power ERP is 100W or less, it is assumed that radio waves can reach a distance of 3km or more from the transmission point, and 300 x 10 = 3km is set as the distance corresponding to the maximum point max_pt.

For example, if the mesh size used is 50m square and the transmission point effective radiated power ERP is greater than 100W, and the maximum point max_pt set in step S1005 is less than or equal to 200, the maximum point max_pt is set to 200. This is because, when the transmission point effective radiated power ERP is greater than 100W, it is assumed that radio waves can reach a distance of 10km or more from the transmission point, and 200 x 50 = 10km is set as the distance corresponding to the maximum point max_pt.

Furthermore, if the mesh size used is 50m square and the transmission point effective radiated power ERP is 100W or less, and the maximum point max_pt set in step S1005 is 60 or less, the maximum point max_pt is set to 60. This is because, when the transmission point effective radiated power ERP is 100W or less, it is assumed that radio waves can reach a distance of 3km or more from the transmission point, and 60 x 50 = 3km is set as the distance corresponding to the maximum point max_pt.

In this way, in process 1c, the maximum point setting unit 31 identifies the electric field E at the specified point for each step number p_step from the electric field E at each profile point from the virtual reception point to the transmission point, sets the maximum point max_pt by comparing the electric field E at the specified point with the required electric field min_se, and corrects the maximum point max_pt according to the transmission point effective radiated power ERP.

If process 1c were to be performed from the transmission point to the virtual reception point, the electric field E between the transmission point and the target maximum point max_pt would fluctuate due to factors such as unevenness of the terrain, and there would be many profile points where the electric field E is greater than the required electric field min_se, which would result in a high processing load and take a long time to set the maximum point max_pt.

In contrast, by performing process 1c from the virtual reception point to the transmission point, it is possible to find the profile point where the electric field E is first determined to be equal to or greater than the required electric field min_se, thereby reducing the processing load and achieving faster processing. In particular, when the effective radiated power ERP of the transmission point is large, the virtual reception point will be located farther away, further reducing the processing load and increasing the processing speed.

In addition, since processing is performed for each step number p_step, the number of processing times can be reduced compared to processing for each profile point, thereby reducing the processing load and speeding up processing.

The maximum point setting unit 31 calculates the number of steps p_step by dividing the number of profile points p_count by, for example, a positive integer, 10 (see equation (5) above), and sets designated points for each profile point spaced at intervals of the number of steps p_step from the virtual reception point to the transmission point.If the electric field E at the designated point is equal to or greater than the required electric field min_se, the number of steps p_step is added to the designated point, and the profile point indicated by the addition result is set as the maximum point max_pt.

In response to this, the maximum point setting unit 31 may determine whether the electric field E of the profile points from the virtual reception point to the transmission point is greater than or equal to the required electric field min_se, and set the profile point at which it is first determined that the electric field E is greater than or equal to the required electric field min_se as the maximum point max_pt.

(Process 1d)
Next, a detailed description will be given of process 1d (field averaging process) in step S704 shown in Fig. 7. Fig. 11 is a flowchart showing an example of process 1d, and Fig. 24 is a diagram explaining an example of process 1d.

As mentioned above, process 1d averages a predetermined number of consecutive profile points for the electric field E between the transmission point and the maximum point max_pt, and sets the electric field E between the profile points after the maximum point max_pt and the virtual reception point to 0.

The maximum point setting unit 31 proceeds to step S1102 for profile points between the transmission point and the maximum point max_pt, and proceeds to step S1105 for profile points between profile points after the maximum point max_pt and the virtual reception point (step S1101).

The maximum point setting unit 31 changes the electric field E at the profile points between the transmission point and the maximum point max_pt so that it becomes constant (step-like) at intervals of the distance step number stp (step S1102).

The maximum point setting unit 31 proceeds from step S1102 and calculates the average value of the electric field E of three consecutive profile points (the profile point and those before and after it) for each profile point (step S1103).The maximum point setting unit 31 then sets this average value as the electric field E of the central profile point of the three profile points (step S1104).

This allows for an overall smooth electric field E to be obtained from the constant electric field E at profile points spaced apart by the distance step number stp.

On the other hand, the maximum point setting unit 31 sets the electric field E = 0 for each profile point between the profile point after the maximum point max_pt and the virtual reception point (step S1105).

In this way, in process 1d, the maximum point setting unit 31 averages a predetermined number of consecutive profile points for the electric field E between the transmission point and the maximum point max_pt, and sets the electric field E between the profile points after the maximum point max_pt and the virtual reception point to 0.

As a result, the electric field E between the transmission point and the maximum point max_pt is averaged over the electric field E of three consecutive profile points, thereby suppressing fluctuations in the electric field E due to slight topographical undulations in the short distance. In particular, fluctuations in the electric field E around the required electric field min_se can be suppressed, which reduces the amount of calculation required when comparing the electric field E with the required electric field min_se in process 2a, etc., described below, thereby reducing the processing load and speeding up processing.

In addition, because the electric field E between the profile points after the maximum point max_pt and the virtual reception point is set to 0, profile points in that range can be excluded from processing in process 2a, etc., described below, thereby reducing the processing load and speeding up processing.

(Farthest point setting process from the transmission point to a distant location)
Next, a detailed description will be given of the process 2 of step S405: the process of setting the most distant point from the transmission point to a distant location by the most distant point setting unit 32 shown in Fig. 4. Fig. 12 is a flowchart showing an example of the process 2: the process of setting the most distant point from the transmission point to a distant location (step S405).

The farthest point setting unit 32 calculates the maximum width max1 at which the electric field E is equal to or greater than the required electric field min_se from the transmission point toward the farthest maximum point max_pt, and sets the farthest point max_p (step S1201, process 2a).

The farthest point setting unit 32 calculates the maximum width max2 at which the electric field E is less than the required electric field min_se from the transmission point toward the farthest point max_p, and sets the farthest point min_p (step S1202, process 2b).

If the maximum width max2 when the farthest point min_p is set is wider than the predetermined value, the farthest point setting unit 32 resets the farthest point max_p between the transmission point and the farthest point min_p using the same processing as in step S1201 (step S1203, process 2c).

The farthest point setting unit 32 determines whether the farthest point max_p is closer to the transmission point than the farthest point min_p, and sets the area vertex coordinates area_data[hoko].ido,keido that define the broadcast area (step S1204, process 2d).

The farthest point setting unit 32 may set the coordinates of the maximum point max_pt set in process 1c of step S703 in FIG. 7 as the area vertex coordinates area_data[hoko].ido,keido. The farthest point setting unit 32 may also set the coordinates of the farthest point max_p set in process 2a of step S1201 as the area vertex coordinates area_data[hoko].ido,keido.

(Process 2a)
Next, a detailed description will be given of process 2a (setting process of max_p, the farthest point equal to or greater than the required electric field min_se) in step S1201 shown in Fig. 12. Fig. 13 is a flowchart showing an example of process 2a, and Fig. 25 is a diagram for explaining an example of process 2a.

As mentioned above, process 2a calculates the maximum width max1 from the transmission point toward the farthest maximum point max_pt, at which the electric field E is equal to or greater than the required electric field min_se, and sets the farthest point max_p.

The farthest point setting unit 32 calculates the width from the transmission point to the maximum point max_pt where the electric field E is equal to or greater than the required electric field min_se, identifies the widest width, and sets the maximum width max1 (step S1301).

For example, in the lower diagram of Figure 25, from the transmission point toward the maximum point max_pt, first the width EW1 at which the electric field E is greater than or equal to the required electric field min_se is calculated, and the maximum width max1 = EW1 is set. Then the width EW2 at which the electric field E is greater than or equal to the required electric field min_se is calculated, and because EW1 > EW2, the maximum width max1 = EW1 is maintained. Next, the width EW3 at which the electric field E is greater than or equal to the required electric field min_se is calculated, and because EW1 < EW3, the maximum width max1 = EW3 is set. Then, processing continues toward the maximum point max_pt, but because no width at which the electric field E is greater than or equal to the required electric field min_se is calculated, the maximum width max1 = EW3 is determined.

Returning to Figure 13, the farthest point setting unit 32 sets the profile point closest to the maximum point max_pt (farthest from the transmission point) among the profile points included in the points of maximum width max1 as the farthest point max_p (step S1302).

For example, in the lower diagram of Figure 25, of the profile points 350 to 530 included in the point where the maximum width max1 = EW3, the profile point 530 closest to the maximum point max_pt is set as the farthest point max_p.

In this way, in process 2a, the farthest point setting unit 32 processes the profile points between the transmission point and the farthest maximum point max_pt, calculates the maximum width max1, and sets the farthest point max_p.

As a result, of the profile points between the transmission point and the virtual reception point, the profile points between the maximum point max_pt and the virtual reception point are not processed, thereby reducing the processing load and speeding up processing.

(Process 2b)
Next, a detailed description will be given of process 2b (processing for setting the farthest point min_p less than the required electric field min_se) in step S1202 shown in Fig. 12. Fig. 14 is a flowchart showing an example of process 2b, and Fig. 26 is a diagram for explaining an example of process 2b.

As mentioned above, process 2b calculates the maximum width max2 from the transmission point toward the farthest point max_p, at which the electric field E is less than the required electric field min_se, and sets the farthest point min_p.

The farthest point setting unit 32 calculates the width from the transmission point to the farthest point max_p at which the electric field E is less than the required electric field min_se, identifies the widest width, and sets the maximum width max2 (step S1401).

For example, in the lower diagram of Figure 26, from the transmission point to the farthest point max_p, first the width EW1 at which the electric field E is less than the required electric field min_se is calculated, and the maximum width max2 = EW1 is set. Then the width EW2 at which the electric field E is less than the required electric field min_se is calculated, and because EW1 < EW2, the maximum width max2 = EW2 is set. Then, processing is performed toward the farthest point max_p, but because no width at which the electric field E is less than the required electric field min_se is calculated, the maximum width max2 = EW2 is determined.

Returning to FIG. 14, the farthest point setting unit 32 sets the profile point closest to the farthest point max_p (farthest from the transmission point) among the profile points included in the points of maximum width max2 as the farthest point min_p (step S1402).

For example, in the lower diagram of Figure 26, of the profile points 300 to 350 included in the point where the maximum width max2 = EW2, the profile point 350 closest to the farthest point max_p is set as the farthest point min_p.

In this way, in process 2b, the farthest point setting unit 32 processes the profile points between the transmission point and the farthest point max_p, calculates the maximum width max2, and sets the farthest point min_p.

As a result, of the profile points between the transmission point and the virtual reception point, the profile points between the farthest point max_p and the virtual reception point are not processed, thereby reducing the processing load and speeding up processing.

(Process 2c)
Next, a detailed description will be given of process 2c: the process of resetting the farthest point max_p in step S1203 shown in Fig. 12. Fig. 15 is a flowchart showing an example of process 2c, and Fig. 27 is a diagram for explaining an example of process 2c.

As mentioned above, process 2c is a process that resets the farthest point max_p using the same process as step S1201 in process 2a if the maximum width max2 when the farthest point min_p is set is wider than a predetermined value.

The farthest point setting unit 32 determines whether the maximum width max2 calculated in step S1401 of process 2b shown in FIG. 14 is wider than a predetermined value (e.g., 10 km) (step S1501).

If the farthest point setting unit 32 determines in step S1501 that the maximum width max2 is wider than the predetermined value (step S1501: Y), it determines that it is inappropriate for the farthest point max_p to be set farther away than the farthest point min_p.

It is inappropriate for the farthest point max_p to be set farther than the farthest point min_p because, when the maximum width max2 is wider than a specified value, even if there is a maximum width max2 between the transmission point and the farthest point max_p, where radio waves cannot reach, it is not appropriate for there to be a farthest point max_p where radio waves can reach beyond the section of maximum width max2. For this reason, the farthest point max_p should be reset.

The farthest point setting unit 32 then calculates the width from the transmission point to the farthest point min_p where the electric field E is equal to or greater than the required electric field min_se, identifies the widest width, and sets the maximum width max3 (step S1502).

For example, in the lower diagram of Figure 27, from the transmission point to the farthest point min_p, first the width EW1 at which the electric field E is greater than or equal to the required electric field min_se is calculated, and the maximum width max3 = EW1 is set. Then the width EW2 at which the electric field E is greater than or equal to the required electric field min_se is calculated, and because EW1 > EW2, the maximum width max3 = EW1 is maintained. Then, processing is performed toward the farthest point min_p, but because no width at which the electric field E is greater than or equal to the required electric field min_se is calculated, the maximum width max3 = EW1 is determined.

Returning to Figure 15, the farthest point setting unit 32 resets the farthest point max_p to the profile point closest to the farthest point min_p (farthest from the transmission point) among the profile points included in the points of maximum width max3 (step S1503).

For example, in the lower diagram of Figure 27, of the profile points 0 to 180 included in the point of maximum width max3 = EW1, profile point 180, which is closest to the farthest point min_p, is reset as the farthest point max_p.

Returning to FIG. 15, on the other hand, if the farthest point setting unit 32 determines in step S1501 that the maximum width max2 is not wider than the predetermined value (step S1501: N), it terminates the processing.

In this way, in process 2c, if the maximum width max2 when the farthest point min_p is set is wider than a predetermined value, the farthest point setting unit 32 processes the profile points between the transmission point and the farthest point min_p, calculates the maximum width max3, and resets the farthest point max_p.

As a result, when the maximum width max2 is wider than a specified value, an appropriate farthest point max_p can be obtained instead of an inappropriate farthest point max_p. Furthermore, when resetting the farthest point max_p, of the profile points between the transmission point and the virtual reception point, the profile points between the farthest point min_p and the virtual reception point are excluded from processing, thereby reducing the processing load and speeding up processing.

(Process 2d)
Next, a detailed description will be given of process 2d: area vertex coordinates area_data[hoko].ido,keido setting process in step S1204 shown in Fig. 12. Fig. 16 is a flowchart showing an example of process 2d, and Fig. 28 is a diagram for explaining an example of process 2d.

As mentioned above, process 2d determines whether the farthest point max_p is closer to the transmission point than the farthest point min_p, and sets the area vertex coordinates area_data[hoko].ido,keido.

The farthest point setting unit 32 determines whether the farthest point max_p is closer to the transmission point than the farthest point min_p (farthest point max_p < farthest point min_p) (step S1601). If the farthest point setting unit 32 determines in step S1601 that the farthest point max_p is closer to the transmission point than the farthest point min_p (step S1601: Y, farthest point max_p < farthest point min_p), it proceeds to step S1602. On the other hand, if the farthest point setting unit 32 determines in step S1601 that the farthest point max_p is not closer to the transmission point than the farthest point min_p (step S1601: N, farthest point max_p ≧ farthest point min_p), it proceeds to step S1609.

When it is determined that the farthest point max_p is closer to the transmission point than the farthest point min_p, this corresponds to the case in process 2c shown in Figure 15 where the maximum width max2 is determined to be wider than the predetermined value and the farthest point max_p is reset. On the other hand, when it is determined that the farthest point max_p is not closer to the transmission point than the farthest point min_p, this corresponds to the case in process 2c shown in Figure 15 where the maximum width max2 is determined to be wider than the predetermined value and the farthest point max_p is not reset.

The farthest point setting unit 32 proceeds from step S1601 (Y) and sets the farthest point max_p to the parameter upt (step S1602), and sets profile points from the point of parameter upt toward the maximum point max_pt (step S1603). Each time the process proceeds from step S1602 or step S1608 (described later), profile points are set in order from the point of parameter upt toward the maximum point max_pt.

The farthest point setting unit 32 calculates the width from the point of parameter upt toward the maximum point max_pt at which the electric field E is less than the required electric field min_se, sets this as the maximum width dspan, and updates the point of parameter upt (step S1604). For details on updating the point of parameter upt, see step S1805 in Figure 18, which will be described later. Here, if a width wider than the initially set maximum width dspan is subsequently calculated from the point of parameter upt toward the maximum point max_pt, this width is set as the new maximum width dspan.

The farthest point setting unit 32 calculates the initial width A from the point of parameter upt toward the maximum point max_pt at which the electric field E is equal to or greater than the required electric field min_se (step S1605).

The farthest point setting unit 32 multiplies the maximum width dspan by, for example, 1.5, and determines whether the width A is wider than the multiplication result (step S1606). If the farthest point setting unit 32 determines in step S1606 that the width A is wider than the multiplication result (step S1606: Y), it calculates the coordinates of the profile point (the latitude and longitude of the profile point closest to the maximum point max_pt at the point of width A) and sets these coordinates as the area vertex coordinates area_data[hoko].ido,keido (step S1607). The coordinates of the profile point are calculated based on the position of the profile point between the farthest point max_p and the virtual reception point, the target direction hoko, and the latitude and longitude of the transmission point included in the transmission information.

In addition, after the area vertex coordinates area_data[hoko].ido,keido are set in the same target direction hoko, the process may proceed from step S1608 (described below) to step S1603, a new profile point may be set, and new area vertex coordinates area_data[hoko].ido,keido may be reset in step S1607.

Also, if the maximum width dspan is not set in step S1604, if there is no width A where the electric field E is equal to or greater than the required electric field min_se in step S1605, or if the conditions are not met in step S1606, the area vertex coordinates area_data[hoko].ido,keido are not set in step S1607. In this case, the farthest point setting unit 32 sets the coordinates of the farthest point max_p reset in step S1503 of Figure 15 as the area vertex coordinates area_data[hoko].ido,keido.

On the other hand, if the farthest point setting unit 32 determines in step S1606 that width A is not wider than the multiplication result (step S1606: N), it proceeds to step S1608.

The farthest point setting unit 32 proceeds from step S1607 or step S1606 (N) to determine whether processing of all profile points has been completed (step S1608). If the farthest point setting unit 32 determines in step S1608 that processing of all profile points has not been completed (step S1608: N), it proceeds to step S1603. The farthest point setting unit 32 then performs the processing of steps S1603 to S1607.

Then, if the farthest point setting unit 32 determines in step S1608 that processing of all profile points has been completed (step S1608: Y), it terminates the processing.

For example, in the lower diagram of Figure 28, from the point of parameter upt to the maximum point max_pt, at profile point 200, width B1 is calculated where the electric field E is less than the required electric field min_se, and maximum width dspan = B1 is set. Then, at profile point 300, width A1 is calculated where the electric field E is greater than or equal to the required electric field min_se. At this time, maximum width dspan = B1, and A1 > dspan × 1.5, so the coordinates of profile point 300 are set as the area vertex coordinates area_data[hoko].ido,keido.

At profile point 350, the width B2 at which the electric field E is less than the required electric field min_se is calculated, and since B1 < B2, the maximum width dspan = B2 is set. Processing then continues toward the maximum point max_pt, but since no width at which the electric field E is less than the required electric field min_se is calculated, the maximum width dspan = B2 is maintained.

At profile point 530, width A2 is calculated, where the electric field E is greater than or equal to the required electric field min_se. At this time, maximum width dspan = B2, and A2 > dspan × 1.5, so the coordinates of profile point 530 are reset to the area vertex coordinates area_data[hoko].ido,keido. Processing then continues toward the maximum point max_pt, but because no width is calculated where the electric field E is greater than or equal to the required electric field min_se, the coordinates of profile point 530 are determined as area vertex coordinates area_data[hoko].ido,keido.

Returning to FIG. 16, the farthest point setting unit 32 proceeds from step S1601 (N), calculates the coordinates of the farthest point max_p, sets these coordinates as the area vertex coordinates area_data[hoko].ido,keido (step S1609), and ends the processing.

In this way, in process 2d, if the farthest point max_p is closer to the transmission point than the farthest point min_p (if the farthest point max_p is reset by process 2c), the farthest point setting unit 32 calculates the maximum width dspan from the farthest point max_p to the maximum point max_pt at which the electric field E is less than the required electric field min_se and the width A at which the electric field E is equal to or greater than the required electric field min_se, and sets the profile point at which the width A exceeds 1.5 times the maximum width dspan and is closest to the maximum point max_pt as the area vertex coordinates area_data[hoko].ido,keido. Furthermore, if the farthest point max_p is not closer to the transmission point than the farthest point min_p, the farthest point setting unit 32 sets the farthest point max_p as the area vertex coordinates area_data[hoko].ido,keido.

As a result, if the farthest point max_p is closer to the transmission point than the farthest point min_p, of the profile points between the farthest point max_p and the maximum point max_pt, the profile points between the farthest point max_p and the maximum point max_pt will be processed, and the profile points between the maximum point max_pt and the virtual reception point will not be processed. This reduces the processing load and speeds up processing.

Furthermore, if the width A where the electric field E is equal to or greater than the required electric field min_se exceeds 1.5 times the maximum width dspan, the farthest point within that width A is set as the area vertex coordinates area_data[hoko].ido,keido. Therefore, areas such as building shadows between the transmission point and that width A where the electric field E is less than the required electric field min_se (maximum widths B1, B2 shown in the lower diagram of Figure 28) are ignored when setting the area vertex coordinates area_data[hoko].ido,keido.

Note that in step S1606, the farthest point setting unit 32 uses 1.5 as the predetermined multiplication value when multiplying the maximum width dspan by a predetermined factor, but the value of 1.5 is an example, and other values may be used. The value by which the maximum width dspan is multiplied is set in advance by the user.

This value of 1.5 was determined by the inventors after extensive research as an appropriate value for excluding building shadows and the like from the broadcast area. By using the value of 1.5, users can accurately determine the validity of the broadcast area calculated by the broadcast area calculation device 1-1.

(Details of process 2d)
Next, a detailed description will be given of steps S1602 to S1608 of process 2d shown in Fig. 16. Fig. 17 is a flowchart showing details (1) of steps S1602 to S1608 of process 2d.

As mentioned above, steps S1602 to S1608 of process 2d are performed when it is determined that the farthest point max_p is closer to the transmission point than the farthest point min_p.

First, the farthest point setting unit 32 sets the parameter upt to the farthest point max_p, the parameter dpt to the profile score p_count, and the maximum width dspan to 1 (step S1701).

The farthest point setting unit 32 proceeds from step S1701 and detects a profile point (i) where the electric field E is less than the required electric field min_se between the profile point at the point of parameter upt (farthest point max_p) and the profile point at the point of profile point count p_count (virtual reception point) (step S1702). Also, in step S1702, the farthest point setting unit 32 proceeds from β in Figure 17 (step S1809 in Figure 18, described later) to detect the next profile point i.

Here, since step S1105 in Figure 11 sets the electric field E = 0 from the maximum point max_pt to the virtual reception point, essentially the processing can be performed from the point of parameter upt to the maximum point max_pt, similar to step S1603 in Figure 16.

The farthest point setting unit 32 determines that the electric field E at profile point i is less than the required electric field min_se or that i≧p_count (step S1703), and proceeds to step S1704.

The farthest point setting unit 32 determines whether the parameter upt = 1 or subtracts the distance of the point of parameter upt (the distance from the transmission point to the point of parameter upt) from the distance of profile point i (the distance from the transmission point to profile point i), and determines whether the result of the subtraction is greater than the result of multiplying the maximum width dspan by 1.5 (step S1704).

If, in step S1704, the farthest point setting unit 32 determines that the above condition is met, i.e., that the parameter upt = 1, or if it determines that the result of subtracting the distance of the point of parameter upt from the distance of profile point i is greater than the result of multiplying the maximum width dspan by 1.5 (step S1704: Y), it calculates the coordinates of profile point (i-1), sets these coordinates as the area vertex coordinates area_data[hoko].ido,keido (step S1705), and proceeds to step S1706.

On the other hand, if the above condition is not met in step S1704 (step S1704: N), the farthest point setting unit 32 proceeds to step S1706.

The farthest point setting unit 32 proceeds from step S1705 or step S1704 (N), sets the parameter dpt to i (step S1706), exits the loop (step S1707), and proceeds to α in Figure 17 (step S1801 in Figure 18, which will be described later).

Figure 18 is a flowchart showing details (2) of steps S1602 to S1608 of process 2d, and is a continuation of Figure 17.

The farthest point setting unit 32 checks whether there is a profile point with a required electric field strength min_se or greater within the judgment distance hantei_kyori. Here, the farthest point setting unit 32 sets the flag flag = False and i = 1 (step S1801).

The judgment distance hantei_kyori is, for example, the result of dividing the maximum distance kyori calculated by the maximum point setting unit 31 in step S807 of Figure 8 by 5.

In other words, the farthest point setting unit 32 subtracts the distance of the profile point dpt (the distance from the transmission point to the profile point dpt) from the distance of the profile point (dpt+i) (the distance from the transmission point to the profile point (dpt+i)).

If the subtraction result is smaller than the judgment distance hantei_kyori, the farthest point setting unit 32 determines whether (dpt + i)≦p_count (step S1802).

If, in step S1802, the farthest point setting unit 32 determines that the subtraction result is smaller than the judgment distance hantei_kyori and (dpt + i)≦p_count (step S1802: Y), it proceeds to step S1803.

On the other hand, if the farthest point setting unit 32 determines in step S1802 that the subtraction result is not smaller than the judgment distance hantei_kyori, or if it determines that (dpt + i)≦p_count is not satisfied (step S1802: N), it proceeds to step S1809.

The farthest point setting unit 32 proceeds from step S1802 (Y) and determines whether the electric field E at the profile point (dpt+i) is equal to or greater than the required electric field min_se (step S1803).

If the farthest point setting unit 32 determines in step S1803 that the electric field E at the profile point (dpt+i) is equal to or greater than the required electric field min_se (step S1803: Y), it sets the flag flag = True, sets the parameter upt to (dpt+i) (step S1805), and proceeds to step S1806.

On the other hand, if the farthest point setting unit 32 determines in step S1803 that the electric field E at the profile point (dpt+i) is not greater than the required electric field min_se (step S1803: N), it sets i = i + 1 (step S1804) and proceeds to step S1802.

The farthest point setting unit 32 proceeds from step S1805, subtracts the distance of the profile point dpt from the distance of the profile point (dpt+i), and determines whether the maximum width dspan is smaller than the result of the subtraction (step S1806).

If the farthest point setting unit 32 determines in step S1806 that the maximum width dspan is smaller than the subtraction result (step S1806: Y), it sets the maximum width dspan to the subtraction result (step S1807) and proceeds to step S1808.

On the other hand, if the farthest point setting unit 32 determines in step S1806 that the maximum width dspan is not smaller than the subtraction result (step S1806: N), it proceeds to step S1808.

The farthest point setting unit 32 proceeds from step S1807 or step S1806 (N), exits the loop (step S1808), and proceeds to step S1809.

The farthest point setting unit 32 proceeds from step S1802 (N) or step S1808 and determines whether the flag is False or whether the parameter upt is greater than the profile score p_count (step S1809).

If, in step S1809, the farthest point setting unit 32 determines that the flag is not False and the parameter upt is not greater than the profile score p_count (step S1809: N), the process proceeds to β in Figure 18 (step S1702 in Figure 17).

On the other hand, if the farthest point setting unit 32 determines in step S1809 that the flag is set to False, or if it determines that the parameter upt is greater than the profile score p_count (step S1809: Y), it terminates the processing.

[Broadcast area correction unit 19]
Next, a detailed description will be given of the broadcast area correction unit 19 shown in Fig. 1. Fig. 19 is a flowchart showing an example of processing by the broadcast area correction unit 19 (step S203).

The broadcast area correction unit 19 reads out broadcast area information from the broadcast area information storage unit 18 (step S1901). As mentioned above, the broadcast area information is the area vertex coordinates area_data[hoko].ido,keido that define the broadcast area. The area vertex coordinates area_data[hoko].ido,keido consist of the latitude and longitude of the area vertex for each target direction hoko, which is obtained by dividing the horizontal 360 degrees from the transmission point by the number of angular direction steps hoko_step.

The broadcast area correction unit 19 calculates the distance from the transmission point to the position of each area vertex indicated by the area vertex coordinates area_data[hoko].ido,keido (the distance to each area vertex). Then, based on the distance to each area vertex, the broadcast area correction unit 19 averages the positions of each area vertex in the following steps S1902 to S1904.

For an area vertex in the target direction hoko, the broadcast area correction unit 19 determines whether the area vertex protrudes from other area vertices and whether it is recessed into them, based on the distance to the area vertex and the distances to a predetermined number of other area vertices adjacent to the area vertex.

If the broadcast area correction unit 19 determines that the area vertex in question protrudes from the other area vertices, it sets new area vertex coordinates area_data[hoko].ido,keido for the area vertex in question so as to eliminate the protrusion of the area vertex in question (step S1902).

Furthermore, if the broadcast area correction unit 19 determines that the area vertex in question is cut into another area vertex, it sets new area vertex coordinates area_data[hoko].ido,keido for the area vertex in question so as to eliminate the cut of the area vertex in question (step S1903).

On the other hand, if the broadcast area correction unit 19 determines that the area vertex does not protrude relative to other area vertices and has not been cut out, it maintains the area vertex coordinates area_data[hoko].ido,keido of the area vertex.

After completing steps S1902 and S1903, the broadcast area correction unit 19 calculates the average distance between a predetermined number of adjacent area vertices, including the area vertex in the target direction hoko. The broadcast area correction unit 19 then corrects the new area vertex coordinates area_data[hoko].ido,keido of the area vertex to the latitude and longitude corresponding to the average value (step S1904).

The broadcast area correction unit 19 outputs the new corrected area vertex coordinates area_data[hoko].ido,keido to the broadcast area drawing unit 20 as broadcast area information (step S1905).

In this way, the broadcast area correction unit 19 corrects each area vertex indicated by the area vertex coordinates area_data[hoko].ido,keido by averaging it based on the positions of a predetermined number of adjacent area vertices.

This reduces the unevenness of each area vertex relative to the transmission point, resulting in a broadcast area with a smooth curve. For example, if there is a building near an area vertex, that area vertex may cut into a certain number of other adjacent area vertices. Since radio waves travel around buildings and reach further, it would be unnatural for that area vertex to cut into them.

In such cases, the broadcast area correction unit 19 can correct the area vertices by moving the indented area vertices to more realistic positions, resulting in a highly accurate broadcast area.

As described above, according to the broadcast area calculation device 1-1 of Example 1, in preprocessing, the broadcast area calculation unit 17 calculates the maximum distance kyori2 based on the transmission point effective radiated power ERP and the required electric field min_se, and performs processes 1a to 2d for each target direction hoko within 360 degrees horizontally, based on the transmission point.

In process 1a, the broadcast area calculation unit 17 calculates the antenna directivity ant_loss for each vertical angle j of the transmitting antenna, defines the antenna directivity ant_loss that maximizes the antenna gain (minimizes loss) as a_loss, and calculates the maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss.

This allows us to obtain the maximum distance kyori from the maximum distance kyori2, taking into account the minimum loss due to the antenna directivity ant_loss.

In process 1b, the broadcast area calculation unit 17 calculates the electric field E for each profile point between the transmission point and the virtual reception point corresponding to the maximum distance kyori, and calculates the number of profile points p_count and the number of steps p_step. The broadcast area calculation unit 17 then corrects the number of steps p_step according to the mesh size used.

As a result, the number of steps p_step calculated in process 1b is used to set designated points when processing each designated point that is coarser than the profile points in process 1c, thereby reducing the processing load and speeding up processing. Furthermore, because the number of steps p_step does not become larger than necessary depending on the mesh size, the calculations in process 1c do not become coarse, ensuring calculation accuracy.

In process 1c, the broadcast area calculation unit 17 sets designated points for each profile point spaced at intervals of the step number p_step from the virtual reception point toward the transmission point, determines whether the electric field E at the designated point is equal to or greater than the required electric field min_se, adds the step number p_step to the designated point when it determines that the electric field E at the designated point is equal to or greater than the required electric field min_se, and sets the profile point indicated by the addition result as the maximum point max_pt. The broadcast area calculation unit 17 then corrects the maximum point max_pt according to the transmission point effective radiated power ERP.

As a result, processing is performed from the virtual reception point to the transmission point, and the profile point where the electric field E is first determined to be equal to or greater than the required electric field min_se is set as the maximum point max_pt. This reduces the processing load and speeds up processing compared to processing from the transmission point to the virtual reception point.

In addition, since processing is performed for each profile point (each specified point) spaced at intervals of the step number p_step, it is possible to reduce the processing load and speed up processing compared to processing for each profile point. Furthermore, if the distance from the transmission point to the maximum point max_pt is shorter than the distance preset in accordance with the transmission point effective radiated power ERP, the maximum point max_pt is corrected to the profile point corresponding to that distance. Therefore, the maximum point max_pt can be set to an appropriate point in accordance with the transmission point effective radiated power ERP.

In process 1d, the broadcast area calculation unit 17 averages the electric field E between the transmission point and the maximum point max_pt, and sets the electric field E = 0 between the profile points after the maximum point max_pt and the virtual reception point.

This makes it possible to absorb fluctuations in the electric field E due to slight topographical undulations in the short distance between the transmission point and the maximum point max_pt. Furthermore, the area from the profile point after the maximum point max_pt to the virtual reception point can be excluded from processing, thereby reducing the processing load and speeding up processing.

In process 2a, the broadcast area calculation unit 17 calculates the maximum width max1 from the transmission point toward the maximum point max_pt at which the electric field E is equal to or greater than the required electric field min_se, and sets the farthest point max_p.

This means that profile points between the maximum point max_pt and the virtual reception point are not processed, thereby reducing the processing load and speeding up processing.

In process 2b, the broadcast area calculation unit 17 calculates the maximum width max2 from the transmission point toward the farthest point max_p at which the electric field E is less than the required electric field min_se, and sets the farthest point min_p.

This means that profile points between the farthest point max_p and the virtual reception point are not processed, thereby reducing the processing load and speeding up processing.

If the maximum width max2 is greater than the predetermined value in process 2c, the broadcast area calculation unit 17 resets the farthest point max_p from the transmission point toward the farthest point min_p using the same process as process 2a.

This allows an appropriate farthest point max_p to be obtained instead of an inappropriate farthest point max_p. Furthermore, since the profile points between the farthest point min_p and the virtual reception point are not processed, the processing load can be reduced and processing can be sped up.

In process 2d, if the farthest point max_p is closer to the transmission point than the farthest point min_p (if the farthest point max_p was reset in process 2c), the broadcast area calculation unit 17 calculates the maximum width dspan from the farthest point max_p to the maximum point max_pt at which the electric field E is less than the required electric field min_se and the width A at which the electric field E is equal to or greater than the required electric field min_se, and if width A exceeds 1.5 times the maximum width dspan, sets the profile point closest to the maximum point max_pt at the point of width A as the area vertex coordinates area_data[hoko].ido,keido. Furthermore, if the farthest point max_p is not closer to the transmission point than the farthest point min_p, the broadcast area calculation unit 17 sets the farthest point max_p as the area vertex coordinates area_data[hoko].ido,keido.

This means that profile points between the maximum point max_pt and the virtual reception point are not processed, reducing the processing load and speeding up processing. It also makes it possible to ignore shadows of buildings and other objects that exist between the transmission point and the width A and cause the electric field E to be less than the required electric field min_se, allowing for highly accurate setting of area vertex coordinates area_data[hoko].ido,keido.

The broadcast area correction unit 19 corrects the area vertex coordinates area_data[hoko].ido,keido, such as by eliminating protrusions and cuts in the area vertices, so that the shape (broadcast area shape) formed by connecting the area vertices at the area vertex coordinates area_data[hoko].ido,keido set by the broadcast area calculation unit 17 becomes smooth.

The broadcast area drawing unit 20 generates a display signal for drawing the broadcast area on a map based on the corrected area vertex coordinates area_data[hoko].ido,keido, and outputs the display signal to the display device 2.

This allows for the broadcast area that satisfies the required electric field min_se to be calculated accurately and quickly.

Example 2
Next, a description will be given of a broadcast area calculation device according to Example 2. The broadcast area calculation device according to Example 2 is characterized in that, in the broadcast area calculation device 1-1 according to Example 1, the broadcast area is corrected using land use data for each mesh so that sea areas are not included in the broadcast area.

According to Example 2, a broadcast area is set that does not include ocean areas, making it possible to exclude uninhabited areas from the broadcast area.

Figure 29 is a block diagram showing an example configuration of a broadcast area calculation device according to Example 2. This broadcast area calculation device 1-2 includes a required electric field input unit 10, a constant memory unit 11, a transmission point information memory unit 12, a topographical height data memory unit 13, a land reflection coefficient memory unit 14, a land use data memory unit 15, a land reflection coefficient calculation unit 16, a broadcast area calculation unit 17, a broadcast area information memory unit 18, a broadcast area correction unit 21, and a broadcast area drawing unit 20.

Comparing the broadcast area calculation device 1-1 of Example 1 and the broadcast area calculation device 1-2 of Example 2 shown in Figure 1, the broadcast area calculation device 1-2 differs from the broadcast area calculation device 1-1 in that it is equipped with a broadcast area correction unit 21 that is different from the broadcast area correction unit 19 equipped in the broadcast area calculation device 1-1. Both broadcast area calculation devices 1-1 and 1-2 have the same components except for the broadcast area correction units 19 and 21. In Figure 29, parts that are common to Figure 1 are assigned the same reference numerals as in Figure 1, and detailed explanations of these parts will be omitted.

The broadcast area correction unit 21 reads the area vertex coordinates area_data[hoko].ido,keido, which are broadcast area information, from the broadcast area information storage unit 18. Then, similar to the broadcast area correction unit 19 shown in Figure 1, the broadcast area correction unit 21 corrects the area vertex coordinates area_data[hoko].ido,keido, such as by eliminating protrusions and cuts in the area vertices, so that the shape connecting the area vertices (broadcast area shape) becomes smooth.

The broadcast area correction unit 21 reads the land use data for the position of the corrected area vertex coordinates area_data[hoko].ido,keido from the land use data storage unit 15. Then, if the land use data is a sea area, the broadcast area correction unit 21 re-corrects the area vertex coordinates area_data[hoko].ido,keido by moving the area vertex toward the transmission point so that the area vertex does not fall within the sea area mesh.

The broadcast area correction unit 21 outputs the re-corrected area vertex coordinates area_data[hoko].ido,keido to the broadcast area drawing unit 20.

Figure 30 is a flowchart showing an example of processing (corresponding to step S203) by the broadcast area correction unit 21 in Example 2. The processing in steps S3001 to S3004 is the same as the processing in steps S1901 to S1904 in Figure 19, so a description thereof will be omitted here.

The broadcast area correction unit 21 proceeds from step S3004 and reads the land use data for the area vertex indicated by the area vertex coordinates area_data[hoko].ido,keido from the land use data storage unit 15 (step S3005).

If the land use data for the area vertex indicates a sea area, the broadcast area correction unit 21 moves the area vertex toward the transmission point so that the area vertex does not fall within the sea area mesh (step S3006), and sets the area vertex coordinates after the move to area_data[hoko].ido,keido.

Specifically, if the land use data for an area vertex indicates a sea area, the broadcast area correction unit 21 moves the area vertex toward the transmission point so that the area vertex does not fall within the mesh corresponding to the read land use data (sea area), and reads the land use data for the area vertex after the move from the land use data storage unit 15.

If the land use data for an area vertex indicates a sea area, the broadcast area correction unit 21 moves the area vertex toward the transmission point so that the area vertex does not again fall within the sea area mesh. The broadcast area correction unit 21 repeats this process until the area vertex no longer falls within the sea area mesh, thereby identifying area vertices whose land use data is not a sea area, and sets the moved area vertex coordinates area_data[hoko].ido,keido.

The broadcast area correction unit 21 proceeds from step S3006 and outputs the moved area vertex coordinates area_data[hoko].ido,keido to the broadcast area drawing unit 20 as corrected broadcast area information (step S3007).

As described above, according to the broadcast area calculation device 1-2 of Example 2, the broadcast area correction unit 21 reads from the land use data storage unit 15 the land use data for the area vertex coordinates area_data[hoko].ido,keido, where protrusions and notches of the area vertices have been removed. If the land use data is a sea area, the broadcast area correction unit 21 then moves the area vertex toward the transmission point so that the land use data for the area vertex is not a sea area, and re-corrects the area vertex coordinates area_data[hoko].ido,keido.

This achieves the same effects as in Example 1. In addition, because a broadcast area is set that does not include ocean areas, uninhabited areas can be excluded from the broadcast area.

The broadcast area correction unit 21 may read the land reflection coefficient for the position of the corrected area vertex coordinates area_data[hoko].ido,keido from the land reflection coefficient storage unit 14, and determine whether the position of the corrected area vertex coordinates area_data[hoko].ido,keido is an ocean area based on the land reflection coefficient. If the broadcast area correction unit 21 determines that the position of the corrected area vertex coordinates area_data[hoko].ido,keido is an ocean area, it re-corrects the area vertex coordinates area_data[hoko].ido,keido by moving the area vertex toward the transmission point so that the area vertex does not fall within the mesh of the ocean area.

Example 3
Next, a description will be given of a broadcast area calculation device according to Example 3. The broadcast area calculation device according to Example 3 is characterized in that, when calculating the broadcast area in the broadcast area calculation device 1-1 according to Example 1, mesh areas whose land use data indicate sea areas are excluded from the processing target.

According to Example 3, mesh areas representing ocean areas are excluded from the processing target, allowing for fast calculation of the broadcast area, and because a broadcast area is set that does not include ocean areas, uninhabited areas can be excluded from the broadcast area.

Figure 31 is a block diagram showing an example configuration of a broadcast area calculation device according to a third embodiment. This broadcast area calculation device 1-3 includes a required electric field input unit 10, a constant memory unit 11, a transmission point information memory unit 12, a topographical height data memory unit 13, a land reflection coefficient memory unit 14, a land use data memory unit 15, a land reflection coefficient calculation unit 16, a broadcast area calculation unit 22, a broadcast area information memory unit 18, a broadcast area correction unit 19, and a broadcast area drawing unit 20.

Comparing the broadcast area calculation device 1-1 of Example 1 shown in Figure 1 with the broadcast area calculation device 1-3 of Example 3, the broadcast area calculation device 1-3 differs from the broadcast area calculation device 1-1 in that it is equipped with a broadcast area calculation unit 22 that is different from the broadcast area calculation unit 17 equipped in the broadcast area calculation device 1-1. Both broadcast area calculation devices 1-1 and 1-3 have the same components except for the broadcast area calculation units 17 and 22. In Figure 31, parts that are common to Figure 1 are assigned the same reference numerals as in Figure 1, and detailed explanations of these parts will be omitted.

Similar to the broadcast area calculation unit 17 shown in Figure 1, the broadcast area calculation unit 22 starts the broadcast area calculation process when a start command is input from the required electric field input unit 10. The broadcast area calculation unit 22 uses the required electric fields syoyou_e, syoyou_e2, the number of angular steps hoko_step, transmission point information, topographical height data and land reflection coefficients for each mesh of a predetermined size, etc., to calculate the electric field E in the horizontal 360-degree direction based on the transmission point while excluding from the processing area mesh areas whose land use data indicates sea areas, thereby calculating the broadcast area in which the electric field E at the receiving point satisfies the required electric field min_se, and finds the area vertex coordinates area_data[hoko].ido,keido.

The broadcast area calculation unit 22 stores the area vertex coordinates area_data[hoko].ido,keido as broadcast area information in the broadcast area information storage unit 18.

Specifically, for each target direction hoko, the broadcast area calculation unit 22 reads land use data for each mesh containing the profile point from the land use data storage unit 15 for each profile point between the transmission point and the virtual reception point corresponding to the maximum distance kyori.

When performing the profile calculation in step S903 of process 1b shown in Figure 9, the maximum point setting unit 31 of the broadcast area calculation unit 22 determines whether the land use data for each profile point is a sea area.

If the maximum point setting unit 31 determines that the land use data for a profile point is not a sea area, it calculates the electric field E for that profile point. On the other hand, if the maximum point setting unit 31 determines that the land use data for a profile point is a sea area, it skips that profile point without calculating the electric field E for that profile point, and moves on to processing the next profile point.

The maximum point setting unit 31 and the farthest point setting unit 32 exclude from processing profile points for which the land use data is determined to be a sea area and the electric field E has not been calculated.

In other words, when setting the designated point in step S1001 of process 1c shown in FIG. 10, the maximum point setting unit 31 does not set as a designated point any profile point for which the land use data is determined to be an ocean area and for which the electric field E has not been calculated. In other words, the processes of steps S1002 and S1003 are not performed for profile points for which the land use data is determined to be an ocean area and for which the electric field E has not been calculated.

In addition, in process 1d shown in FIG. 11, the maximum point setting unit 31 excludes profile points for which the land use data is determined to be a sea area and the electric field E is not calculated from the processing targets of steps S1102 to S1104.

In addition, the farthest point setting unit 32 excludes profile points for which the land use data is determined to be an ocean area and for which the electric field E was not calculated in process 2a shown in Figure 13, process 2b shown in Figure 14, and process 2c shown in Figure 15 from the processing targets of steps S1301, S1401, and S1502 (processing is performed so that the profile points are not included in the maximum width max1, etc.). As a result, there are no profile points for which the land use data is an ocean area in the maximum widths max1, max2, and max3, and no profile points for which the land use data is an ocean area are set as the farthest points max_p and min_p.

Furthermore, when setting profile points in step S1603 shown in FIG. 16, the farthest point setting unit 32 does not set profile points for which the land use data is determined to be an ocean area and for which the electric field E has not been calculated. In other words, for profile points for which the land use data is determined to be an ocean area and for which the electric field E has not been calculated, the processing of steps S1604 to S1607 for those profile points is not performed (processing is performed so that those profile points are not included in the maximum width dspan and width A). As a result, there are no profile points for which the land use data is an ocean area within the maximum width dspan and width A, and no profile points for which the land use data is an ocean area are set at the area vertex coordinates area_data[hoko].ido,keido.

As described above, according to the broadcast area calculation device 1-3 of Example 3, the broadcast area calculation unit 22 reads the land use data of the profile points from the land use data storage unit 15, and calculates the electric field E for each profile point while excluding from the processing target mesh areas where the land use data indicates an ocean area, thereby obtaining the area vertex coordinates area_data[hoko].ido,keido. In this case, the broadcast area calculation unit 22 calculates the electric field E for profile points between the transmission point and the virtual reception point where the land use data is not an ocean area, and does not calculate the electric field E for profile points where the land use data is an ocean area.

This allows mesh areas that represent ocean areas to be excluded from processing, making it possible to calculate the broadcast area even faster. Furthermore, because the broadcast area is set to exclude ocean areas, uninhabited areas can be excluded from the broadcast area.

The broadcast area calculation unit 22 may read the land reflection coefficient of each profile point from the land reflection coefficient storage unit 14 and determine whether or not the profile point is an ocean area based on the land reflection coefficient. If the broadcast area calculation unit 22 determines that the profile point is an ocean area, it performs the same processing as when the land use data described above determines that the profile point is an ocean area. If the broadcast area calculation unit 22 determines that the profile point is not an ocean area, it performs the same processing as when the land use data described above determines that the profile point is not an ocean area.

The present invention has been described above using Examples 1 to 3, but the present invention is not limited to these Examples 1 to 3 and can be modified in various ways without departing from the technical concept thereof.

For example, in the above-described Examples 1 to 3, the broadcast area calculation devices 1-1 and 1-3 are equipped with a broadcast area correction unit 19, and the broadcast area calculation device 1-2 is equipped with a broadcast area correction unit 21. The broadcast area correction units 19 and 21 read and correct the broadcast area information from the broadcast area information storage unit 18, and output the corrected broadcast area information to the broadcast area drawing unit 20.

In contrast, the broadcast area calculation devices 1-1 and 1-3 may not include the broadcast area correction unit 19, and the broadcast area calculation device 1-2 may not include the broadcast area correction unit 21. In this case, the broadcast area drawing unit 20 reads the broadcast area information from the broadcast area information storage unit 18, generates a display signal, and outputs it to the display device 2. This reduces the circuit size and processing load.

Furthermore, for example, in Examples 1 to 3, the maximum point setting unit 31 of the broadcast area calculation unit 17, 22 calculates the maximum distance kyori from the maximum distance kyori2 in process 1a shown in Figure 8, and then performs processes such as process 1b shown in Figure 9 and process 1c shown in Figure 10 based on the virtual reception point corresponding to the maximum distance kyori.

In contrast, the maximum point setting unit 31 may use maximum distance kyori2 instead of maximum distance kyori, and perform each process based on the virtual reception point corresponding to maximum distance kyori2. In this case, the maximum point setting unit 31 does not need to calculate maximum distance kyori. This reduces the processing load and enables faster processing.

Furthermore, for example, in Examples 1 to 3, the farthest point setting unit 31 of the broadcast area calculation unit 17, 22 performs process 1d shown in Figure 11, but process 1d does not have to be performed. In this case, the farthest point setting unit 32 performs processes 2a to 2d using the electric field E that has not been averaged by process 1d.

Furthermore, for example, in Example 2 above, the broadcast area correction unit 21 of the broadcast area calculation device 1-2 corrects the broadcast area information using land use data for each mesh so that ocean areas are not included in the broadcast area. The present invention does not limit the classification of land use data to be excluded from the broadcast area to ocean areas; the broadcast area information may be corrected so as not to include areas classified as other than ocean areas, or so as not to include areas with multiple classifications such as ocean areas or areas with multiple classifications other than ocean areas.

Furthermore, for example, in Example 3, when calculating the broadcast area, the broadcast area calculation unit 22 of the broadcast area calculation device 1-3 excludes from the processing target mesh areas for which land use data indicates sea areas. The present invention does not limit the land use data excluded from the processing target to sea areas; areas of divisions other than sea areas may be excluded from the processing target, or areas of multiple divisions such as sea areas, or multiple divisions other than sea areas may be excluded from the processing target.

Incidentally, a conventional computer can be used as the hardware configuration of the broadcast area calculation devices 1-1 to 1-3 according to embodiments 1 to 3 of the present invention. The broadcast area calculation devices 1-1 to 1-3 are configured by a computer equipped with a CPU, a volatile storage medium such as RAM, a non-volatile storage medium such as ROM, an interface, etc.

The functions of the required electric field input unit 10, constant memory unit 11, transmission point information memory unit 12, topographic height data memory unit 13, land reflection coefficient memory unit 14, land use data memory unit 15, land reflection coefficient calculation unit 16, broadcast area calculation unit 17, broadcast area information memory unit 18, broadcast area correction unit 19, and broadcast area drawing unit 20 provided in the broadcast area calculation device 1-1 are each realized by having the CPU execute a program that describes these functions.

Furthermore, the functions of the required electric field input unit 10, constant memory unit 11, transmission point information memory unit 12, topographic height data memory unit 13, land reflection coefficient memory unit 14, land use data memory unit 15, land reflection coefficient calculation unit 16, broadcast area calculation unit 17, broadcast area information memory unit 18, broadcast area correction unit 21, and broadcast area drawing unit 20 provided in the broadcast area calculation device 1-2 are each realized by having the CPU execute a program that describes these functions.

Furthermore, the functions of the required electric field input unit 10, constant memory unit 11, transmission point information memory unit 12, topographic height data memory unit 13, land reflection coefficient memory unit 14, land use data memory unit 15, land reflection coefficient calculation unit 16, broadcast area calculation unit 22, broadcast area information memory unit 18, broadcast area correction unit 19, and broadcast area drawing unit 20 provided in the broadcast area calculation device 1-3 are each realized by having the CPU execute a program that describes these functions.

These programs are stored on the storage medium and are read and executed by the CPU. These programs can also be stored and distributed on storage media such as magnetic disks (floppy disks, hard disks, etc.), optical disks (CD-ROMs, DVDs, etc.), and semiconductor memory, and can also be sent and received over a network.

1-1, 1-2, 1-3 Broadcast area calculation device 2 Display device 10 Required electric field input unit 11 Constant memory unit 12 Transmission point information memory unit 13 Topographic height data memory unit 14 Land reflection coefficient memory unit 15 Land use data memory unit 16 Land reflection coefficient calculation unit 17, 22 Broadcast area calculation unit 18 Broadcast area information memory unit 19, 21 Broadcast area correction unit 20 Broadcast area drawing unit 30 Pre-processing unit 31 Maximum point setting unit 32 Farthest point setting unit
syoyou_e, syoyou_e2, min_se required electric field
hoko_step Number of steps in the angle direction
stp Number of steps in the distance direction
ERP Effective radiated power at transmitting point
kyori2, kyori maximum distance
hoko Target direction
a_loss, ant_loss(recv_h) Antenna directivity
recv_h Virtual reception point height for calculation
send_h Transmission point height j Vertical angle
hantei_kyori Judgment distance
p_count Profile score
p_step Step number E Electric field
max_pt Maximum point
max1, max2, max3, dspan Maximum width
max_p, min_p Farthest point
area_data[hoko].ido,keido Area vertex coordinates (latitude and longitude)

Claims (8)

A broadcast area calculation device for calculating a broadcast area where terrestrial digital broadcasting can be received,
a broadcast area calculation unit that calculates the latitude and longitude of a group of area vertices of the broadcast area that satisfy a predetermined required electric field min_se for each target direction hoko obtained by dividing 360 degrees horizontally at predetermined angles based on a transmission point of a broadcast station, as area vertex coordinates area_data[hoko].ido,keido;
The broadcast area calculation unit
a pre-processing unit that calculates a maximum distance kyori2 of a receiving point due to free space propagation based on a transmitting point effective radiated power ERP, which is an effective radiated power of a radio wave transmitted from an antenna of the broadcasting station, and the required electric field min_se;
The reception point corresponding to the maximum distance kyori2 calculated by the preprocessing unit is set as a virtual reception point, and the electric field E is calculated for each profile point between the transmission point and the virtual reception point,
a maximum point setting unit that determines whether or not the electric field E is equal to or greater than the required electric field min_se for each profile point from the virtual reception point toward the transmission point, and sets the profile point at which it is first determined that the electric field E is equal to or greater than the required electric field min_se as a maximum point max_pt,
A broadcast area calculation device characterized in that the maximum point max_pt is set to the area vertex coordinates area_data[hoko].ido,keido. 2. The broadcast area calculation device according to claim 1,
Further, a farthest point setting unit for setting the farthest point is provided,
The farthest point setting unit
calculating a maximum width max1 from the transmission point toward the maximum point max_pt set by the maximum point setting unit, at which the electric field E is equal to or greater than the required electric field min_se, and setting the profile point closest to the maximum point max_pt at the point of the maximum width max1 as the farthest point max_p;
calculating a maximum width max2 from the transmission point toward the farthest point max_p at which the electric field E is less than the required electric field min_se, and setting the profile point closest to the farthest point max_p at the point of the maximum width max2 as the farthest point min_p;
determining whether the maximum width max2 is greater than a predetermined value, and if it is determined that the maximum width max2 is not greater than the predetermined value, setting the coordinates of the farthest point max_p as the area vertex coordinates area_data[hoko].ido,keido;
If it is determined that the maximum width max2 is wider than a predetermined value, a maximum width max3 is calculated from the transmission point toward the farthest point min_p, at which the electric field E is equal to or greater than the required electric field min_se, and the profile point closest to the farthest point min_p at the point of the maximum width max3 is reset to the farthest point max_p, and is also set to the area vertex coordinates area_data[hoko].ido,keido,
A broadcast area calculation device characterized by sequentially calculating widths from the farthest point max_p to the maximum point max_pt at which the electric field E is less than the required electric field min_se, setting the maximum width as a maximum width dspan, and if the width is greater than the set maximum width dspan, updating the maximum width dspan, calculating a width A at which the electric field E is greater than the required electric field min_se, and if the width A exceeds a predetermined multiple of the maximum width dspan, setting the profile point at the point of width A that is closest to the maximum point max_pt as the area vertex coordinates area_data[hoko].ido,keido. 3. The broadcast area calculation device according to claim 1,
The broadcast area calculation device further comprises a broadcast area correction unit that averages the positions of a predetermined number of adjacent area vertex coordinates area_data[hoko].ido,keido for each target direction hoko calculated by the broadcast area calculation unit. 4. The broadcast area calculation device according to claim 1,
The maximum point setting unit
A broadcast area calculation device characterized by calculating an average value for each profile point between the transmission point and the maximum point max_pt based on the electric field E of a plurality of consecutive profile points including the profile point in question, and setting the average value as the electric field E of the profile point in question. 5. The broadcast area calculation device according to claim 1,
The maximum point setting unit
calculating an antenna directivity ant_loss for each predetermined angle j in the vertical direction of the antenna of the broadcasting station, setting the antenna directivity ant_loss at which the antenna gain is maximized as antenna directivity a_loss, and calculating a maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss;
A broadcast area calculation device characterized in that the maximum distance kyori is used instead of the maximum distance kyori2, a reception point corresponding to the maximum distance kyori is set as the virtual reception point, and the maximum point max_pt is set. 4. The broadcast area calculation device according to claim 3,
Further, a land use data storage unit is provided which stores land use data for each mesh of a predetermined size,
The broadcast area correction unit
A broadcast area calculation device characterized by reading out the land use data at the position of the averaged area vertex coordinates area_data[hoko].ido,keido from the land use data storage unit, and if the land use data is a sea area, moving the position of the averaged area vertex coordinates area_data[hoko].ido,keido toward the transmission point so that the area vertex indicated by the averaged area vertex coordinates area_data[hoko].ido,keido does not fall within the mesh of the sea area. 6. The broadcast area calculation device according to claim 1,
Further, a land use data storage unit is provided which stores land use data for each mesh of a predetermined size,
The maximum point setting unit
reads out the land use data of the profile points between the transmission points and the virtual reception points from the land use data storage unit, and determines whether the land use data of the profile points is a sea area;
A broadcast area calculation device, characterized in that it calculates the electric field E for the profile point when the land use data is not the sea area. A computer constituting a broadcast area calculation device calculates the latitude and longitude of a group of area vertices of a broadcast area that satisfies a predetermined required electric field min_se for each target direction hoko obtained by dividing 360 degrees horizontally at predetermined angles based on the transmitting point of a broadcast station, as area vertex coordinates area_data[hoko].ido,keido,
a pre-processing unit that calculates a maximum distance kyori2 from a receiving point due to free space propagation based on a transmitting point effective radiated power ERP, which is the effective radiated power of radio waves transmitted from an antenna of the broadcasting station, and the required electric field min_se; and
The reception point corresponding to the maximum distance kyori2 calculated by the preprocessing unit is set as a virtual reception point, and the electric field E is calculated for each profile point between the transmission point and the virtual reception point,
determining whether or not the electric field E is equal to or greater than the required electric field min_se for each profile point from the virtual reception point toward the transmission point, and functioning as a maximum point setting unit that sets the profile point at which it is first determined that the electric field E is equal to or greater than the required electric field min_se as a maximum point max_pt;
A program characterized by setting the maximum point max_pt to the area vertex coordinates area_data[hoko].ido,keido.