JPH0260988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a navigation device that calculates a navigation position by converting the intersection of two position lines obtained as the output of a navigation device such as a Loran receiver into latitude and longitude information. It is something.

The output of the Loran receiver, which is a typical example of navigation equipment, is the position line information of the current ship position, which is the measurement point, so the output is the latitude,
It is necessary to use a longitude conversion device. Navigation devices using Loran receivers have a built-in latitude and longitude converter, and are now being put into widespread use as a way to further automate hyperbolic navigation using Loran receivers.

By the way, to determine the current position of a ship using hyperbolic navigation, the intersection of two position lines is found, but for geometric reasons, the greater the hyperbola, that is, the divergence of the position lines, the greater the error in the determined ship position. Furthermore, as the intersection angle θ between the two position lines becomes smaller, the error in the ship's position similarly becomes larger. This will be explained with reference to FIG. Figure A shows two position lines L ₁ and L ₂
are perpendicular to each other at the intersection point P, and the figure (b) shows the case where the two position lines L ₁ and L ₂ intersect at the intersection point P at the intersection angle θ, and ΔL ₁ and ΔL ₂ are determined by fluctuations in radio wave propagation, etc. The resulting error range is shown. From this figure, the shaded areas A and B indicate the overall error range of the ship's position, including radio wave propagation causes and geometric causes.Therefore, the smaller the intersection angle between the two position lines, the more it can be calculated. It can be seen that the error in the ship's position becomes larger.

If the Loran chain used in the above-mentioned Loran navigation device is restricted, many locations shown in FIG. 1B will appear. This deteriorates the accuracy of navigation equipment using the Loran receiver. If there is no restriction on the Loran chain to be used, that is, if Loran A and C chains can be used separately, or if both chains can be mixed and the two position lines can be used hybridly, the navigation device described above can be used. Deterioration of usage accuracy can be prevented.

Figure 4 explains the case where when there is a large geometrical error due to Loran C, the error in the final latitude and longitude information is reduced by using the position line of Loran A and the position line of Loran C. It is a diagram.

In the figure, the intersection point P ₁ of time difference lines L ₁ and L ₂ is the own ship position. When the time difference line L ₂ includes an error Δt ₂ , the intersection of the time difference lines L ₁ and L ₂ varies within the range of P ₂ to P ₃ .

That is, for an error Δt ₂ of the time difference line L ₂ , the time difference line L ₁ fluctuates by Δt ₁ .

The amount of variation Δt ₁ on the time difference line L ₁ is determined by Δt ₁ =Δt ₂ /sinθ.

Now, if we adopt Loran A for time difference line L ₂ ,
The nominal accuracy of Loran A is 1 μsec.

Therefore, the amount of variation Δt ₁ A in the time difference line L ₁ direction is Δt ₁ A = 1/sinθ = 1 (μsec), and if the time difference lines L ₁ and L ₂ are orthogonal, Δt ₁ A = 1/ 1=1 (μsec).

In other words, if the time difference lines are approximately perpendicular to each other, the measurement error will be 1 μsec when measuring Loran A and C in combination.

Next, if the time difference lines L ₁ and L ₂ are both Loran C,
Since the nominal accuracy of Loran C is 0.1 μsec, the error Δt _1c in the time difference line L ₁ direction is Δt _1c =0.1/sinθ.

The time difference line L ₁ when this error Δt _1c becomes equal to the error 1 μsec in the combination of Loran A and C
When calculating the intersection angle θ _between

As is clear from this, when position measurement is performed using Loran C on time difference lines L ₁ and L ₂ , when the intersection angle of the time difference lines becomes 5.7°, Loran A is used on time difference line L ₂ .
It is equal to the error when positioning is performed using time difference lines L ₁ and L ₂ in orthogonal state.

In other words, when the intersection angle between time difference lines L ₁ and L ₂ is 5.7° or less, it is better to measure the position using the combination of Loran C and A, whose time difference lines are perpendicular to each other, than to perform positioning using the combination of Loran C. It can be said that the accuracy of the lines, that is, the accuracy of the obtained latitude and longitude values, is good.

As described above, by using the two position lines of Loran A and C, higher accuracy can be obtained than positioning using Loran C alone, depending on the own ship's position.

In view of the above, an object of the present invention is to provide a navigation device that can prevent the accuracy of use from deteriorating at any position in the sea area covered by the Loran A chain, Loran C chain, or the like.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a navigation device using a Loran receiver, which is an embodiment of the present invention.

In the figure, a Loran A receiver 1 and a Loran C receiver 2 are each configured independently, and are each capable of outputting a plurality of position line information. A position line selection circuit 4 is connected to the Loran A and C receivers 1 and 2, which selects two predetermined position line information based on the setting position of the selection switch 3 from among the position line information output from them. The circuit 4 calculates the latitude of the intersection point based on the selected position line information,
A latitude/longitude conversion circuit 5 for calculating longitude is connected. In this latitude/longitude conversion circuit 5, if one of the position lines selected by the selection switch 3 and the position line selection circuit 4 is the position line information of Loran C, the station data serving as the reference for the position line is First, the coordinate data is converted into Bethel system coordinate data, and latitude and longitude are determined from the converted values. For this reason, correction values for the above conversion are stored in advance in a geodetic system conversion table 6 constituted by a ROM, and the latitude/longitude conversion circuit 5 is configured to refer to the stored contents of the table 6 as appropriate.

The display 7 displays the latitude determined by the conversion circuit 5,
It consists of a digital display that directly displays the longitude numerically.

Note that the latitude/longitude conversion circuit 5 and the geodetic system conversion table 6 are composed of a microcomputer.

Next, the operation of this device will be explained.

When the Loran A chain is selected by the selection switch 3, the position line selection circuit 4 enables the two position line information from the Loran A receiver 1 and disables the position line information from the Loran C receiver 2. . That is, the latitude and longitude are determined based on the two position line information from the Loran A receiver 1.

In this case, the contents of the geodetic system conversion table 6 are not referred to, and therefore the latitude/longitude conversion circuit 5 calculates the two position line information from the Loran A receiver 1 using the Bessel system coordinates as a reference.

When the selection switch 3 selects the Loran C chain, contrary to the above, the position line selection circuit 4 validates the two position line information from the Loran C receiver 2 and selects the position from the Loran A receiver 1. Disable line information. That is, the latitude and longitude are determined based on the two position line information from the Loran C receiver 2. In this case, the Loran C chain is configured based on the WGS system coordinates, so when calculating latitude and longitude, the geodetic system conversion table 6 is referred to and the station data is converted to data corresponding to the Betssel system. The latitude and longitude calculations described above are executed from here.

Selection switch 3 is Loran A or Loran C
If chain is selected, latitude and longitude calculations are performed as described above.

Next, the operation when the selection switch 3 selects Loran A and C chains will be described.

In this case, the position line selection circuit 4 receives one position line information from the Loran A receiver 1, and receives one position line information from the Loran C receiver 2.
Select another position line information from , and invalidate the other position line information of each receiver. At the same time, the latitude/longitude conversion circuit 5 calculates the latitude and longitude only for the position line information from the Loran C receiver 2 using the geodetic system conversion (WGS system → Betssel system) correction value of the station data. In this way, even if the position line information has different coordinate systems, only one position line information, that is, Loran C
The latitude and longitude of the intersection of both position lines can be determined by simply converting the station data related to the position line information from the receiver 2 into data based on the coordinate system that is the standard for other position line information, that is, the Bethel system coordinates. It will be done. The reason for this is that the position line information is time difference information, that is, distance information, and if the WGS coordinate position of the reference point (transmitting station) is converted to the Bethel system coordinate position, the position line of the Loran C chain is also the position of the Loran A chain. This is because it can be handled simultaneously with lines.

As described above, with a simple configuration, Loran A
The latitude and longitude can be determined by hybridly using the two position lines of the C chain.

Next, the contents of the calculation in the latitude/longitude conversion circuit 5 will be explained with reference to FIG. 3. This figure shows the calculation procedure for determining latitude and longitude using the microcomputer.

Step n ₁ (Hereinafter, step n _x will be simply referred to as n _x )
Then, the station code specified by the Loran receiver, that is, the station code related to the position line information to be used, is input. In n ₂ , the estimated current position of the ship is read. This estimated position may be input from a key not shown, or may be the previous ship position. Next, at _n3 , the location of the station is determined from the station code input at _n1 . The above-mentioned microcomputer has a table memory in which the position of each station is stored in advance in correspondence with each station code, and the position data of the station corresponding to the station code input in _n1 is read from the above-mentioned memory. There is. in this case,
If the station code is of the Loran C chain, the latitude/longitude conversion circuit 5 takes in the correction value for converting from the WGS system to the Bessel system from the geodetic system conversion table 6, and converts the station code of the Loran C chain into the Bethssel system. Converted station data. The work of converting the station data related to the position line information from the Loran C receiver described above into station data based on Betssel system coordinates is executed by _n3 .

Next, in _n4 , it is determined whether position line information is input from the Loran receiver, and if there is no input, the process advances to _n5 . At _n5 , a coordinate conversion coefficient c is obtained that represents a change in latitude and longitude (rad: angular dimension) per unit time shift of a position line (μs: time dimension). This coefficient c is obtained by referring to the estimated position obtained at n ₂ and the station data obtained at n ₃ . Then, the determined coefficient c is temporarily stored until it is determined again in this step, and is placed in a state where it can be used at _n9 , which will be described later.

If position line information is input at _n4 , the process advances to _n6 , where the position line information is taken in. Next, for n ₇ , the position line at the estimated position obtained in n ₂ is determined. This can be done by first finding the distance between the estimated position and the station position obtained in _n3 , and then calculating based on this distance and the degree of radio wave propagation.

Next, in n ₈ , find the difference between the position line of the current ship position obtained in n ₅ and the position line of the estimated position obtained in n ₇ , and in n ₉ , multiply this difference by the coefficient c obtained in n ₅ . , the difference between the current ship position and the estimated position in the angular dimension is determined. Therefore n ₁₀
By adding the estimated position obtained in n ₂ to this difference, the current position can be determined. The result obtained with n ₁₀ is immediately converted into latitude and longitude data after undergoing simple calculations and displayed as n ₁₁ .
Next, at _n12 , the current position obtained at _n10 is used as the estimated position, and the process returns to _n1 . In this case, if the estimated position of n ₂ is too far away from the true current position, an error will occur in the current position determined by n ₁₀ . Therefore, the calculation procedure shown in FIG. 3 is usually repeated several times before completing the calculation.

According to the above-described operations, the latitude and longitude of the current ship position can be determined regardless of whether the two position line information and station data are from either Loran A or C receiver.

Note that it takes a relatively long time to calculate the coordinate transformation coefficient c, so if you calculate the coefficient c after inputting the position line information from the Loran receiver, it will take a long time to calculate the latitude and longitude. It takes time. In this embodiment, as is clear from n ₄ and n ₅ in FIG. 3, the timing for calculating the above coefficients is set to a time when no position line information is input. Therefore, there is an advantage that the time from inputting position line information to displaying latitude and longitude can be extremely short. In this case, even if the estimated position, which is the data necessary to find the coefficient c, that is, the current immediately preceding ship position (see n ₁₂ ), moves slightly, the change in the coefficient c is negligibly small, and the final latitude , has no effect on longitude.

In the above embodiment, the stored contents of the geodetic system conversion table are the correction values for converting station data from the WGS system to the Bessel system, and the calculations for latitude and longitude are performed based on the coordinates of the Bessel system. However, when performing the above calculation based on coordinates in the WGS system, the stored contents of the geodetic system conversion table may be used as correction values for converting station data from the Bessel system to the WGS system. It is also possible to store these correction values together so that the above calculation can be performed using the coordinates of either geodetic system of the Betzel system or the WGS system as a reference. Furthermore, if it is desired to perform the above calculation using the coordinates of another geodetic system as a reference, it is sufficient to change the correction value stored in the geodetic system conversion table for converting into the coordinates.

Note that the correction value for geodetic system conversion is fixed, so by creating station data in advance when the geodetic system is converted based on this correction value and storing it, you can effectively convert the geodetic system. Construct a geodetic system conversion table in which system conversion correction values are stored, thereby n ₃
The station data conversion work can be omitted.

As described above, according to the present invention, different coordinate systems,
For example, since the position lines of the Loran A chain and Loran C chain can be used hybridly, it is possible to find the latitude and longitude with small errors at any point in the sea area covered by these two types of chains. can. In addition, since the coordinate transformation coefficients, which take a relatively long time to calculate, are calculated at a time other than the input timing of the position line information, if the position line information is input, they have already been calculated and can be used by the coefficients. Since the latitude and longitude can be calculated immediately, the time from the input timing of the position line information to the display timing of the latitude and longitude can be extremely shortened, which has the advantage that the accuracy of the obtained latitude and longitude does not deteriorate. There is.

[Brief explanation of the drawing]

Figure 1 A and B show that the error range of the determined ship position differs depending on how the two position lines intersect.
The figure shows a block diagram of a navigation device using a Loran receiver, which is an embodiment of the present invention. Further, FIG. 3 is a flowchart showing the procedure for determining latitude and longitude in the navigation device. FIG. 4 is a diagram explaining the present invention. 1...Loran A receiver, 2...Loran C receiver, 3...Selection switch, 4...Position line selection circuit, 5...Latitude/longitude conversion circuit, 6...Geodetic system conversion table.

Claims (1)

[Claims] 1. A navigation device that determines a ship's position by converting the intersection of two position line information from a navigation device such as a Loran receiver into latitude and longitude information, wherein the navigation device has a different geodetic system. It includes a plurality of devices that output position line information at a predetermined period, and a position line selection means that selects any two position line information from the navigation equipment, and a position line selection means that selects two position line information according to the type of geodetic system of the two position line information. a calculation means that converts latitude and longitude using a desired geodetic system as a reference and includes a geodetic system conversion table storing geodetic system conversion correction values, the calculation means converting position line information into latitude and longitude information. A navigation device comprising means for obtaining coordinate transformation coefficients for transformation at a time other than input timing of position line information. 2 The navigation equipment includes a Loran A receiver and a Loran C receiver, and the geodetic system conversion table is a correction value when converting a geodetic system from the Bessel system to the WGS system, or a correction value when converting the geodetic system from the WGS system to the Bessel system. The navigation device according to claim 1, which is a memory for storing correction values.