JP7570623B2 - Satellite-based positioning method and positioning device - Google Patents

Description

The present invention relates to a positioning method and device using satellites.

In monitoring slope collapse, since the movements of the ground surface that are precursors are small, it is necessary to capture displacements of a few millimeters. It is known to use positioning technology using the Global Navigation Satellite System (GNSS) to capture displacements of the ground surface. Among positioning technologies, the Real Time Kinematic (RTK) method, which is a type of kinematic method, is capable of high-precision positioning in real time. Patent Document 1 discloses a positioning method that achieves measurement accuracy on the millimeter level using the RTK method. In the method of Patent Document 1, displacement is measured from the difference in position information calculated at the time of measurement and at a reference time, which is a time that differs from the measurement time by an integer multiple of a sidereal day, using a combination of satellites that are common to both times.

The RTK method is composed of two calculation steps: an initialization calculation step in which an integer bias corresponding to the path difference of the radio waves received at the measurement point and the reference point is determined (a fix solution is obtained), and then a positioning calculation step in which the position of the measurement point is measured. The initialization time is 10 to 30 seconds in an open sky area, but if there are obstacles such as structural parts in the vicinity, problems such as miss fixes and initialization taking several minutes occur due to the influence of multipath caused by reflected waves. In Non-Patent Document 1, the positioning results are improved by eliminating satellites with poor signal quality. Specifically, an elevation angle mask that eliminates satellites with low elevation angles with large multipath noise, a CN ₀ (carrier power to noise power density ratio) mask that eliminates satellites with low reception sensitivity, satellite system selection, and positioning start timing selection. The selection of the positioning start timing improves the overlooking of cycle slips that occur in specific satellites.

Japanese Patent Application Publication No. 11-352210

"Improving positioning performance by changing the settings of positioning calculation software" Journal of the Japan Society of Civil Engineers, Vol. 72, No. 2, II_47-II_54, 2016

Monitoring for slope collapse requires continuous 24-hour monitoring, and a sufficient number of measurement points must be installed in the estimated slope area. Furthermore, it is usually difficult to secure a power source at the slope collapse monitoring locations. Therefore, long-term measurements are performed using batteries or solar cells, and a system that can reduce power consumption is preferable. Furthermore, since the slope collapse monitoring locations are often mountainous areas with no open sky, initialization of the RTK method takes time, but from the standpoint of power consumption it is desirable to complete the initialization quickly.

The above-mentioned satellite elevation mask, CN ₀ mask, satellite system selection, etc., all reduce the initialization time by excluding specific satellites with large noise. However, each satellite exclusion method has a problem in that it is not possible to determine whether or not the method should be applied before performing the initialization calculation or positioning calculation. Conventionally, one or more satellite exclusion methods are applied to reduce the time of the initialization calculation or positioning calculation.

In view of the above problems, the present invention aims to provide a positioning method and device that uses radio waves from periodic satellites to perform calculations based on the RTK method to determine the position of a measurement point, and that can efficiently select satellites to be excluded from those used in the calculations, thereby shortening the calculation time and performing highly accurate positioning.

In order to solve the above problems, the present invention provides the following configuration.
An embodiment of a positioning method using satellites according to the present invention is a positioning method for positioning a measurement point by an RTK method having an initialization calculation step and a positioning calculation step using radio waves received from a plurality of satellites at a measurement point and a reference point,
A satellite selection step is executed before the initialization calculation step or between the initialization calculation step and the positioning calculation step to select a satellite to be used in a subsequent calculation, and the satellite selection step includes:
a step of excluding satellites other than the periodic satellites having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
Detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
for each said periodic satellite, comparing the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference of at least a predetermined value;
and excluding a periodic satellite determined to have a difference in _CN0 of a predetermined value or more as a satellite not to be used in subsequent calculations.
Another aspect of the positioning method using satellites according to the present invention is a positioning method for performing positioning of a measurement point by an RTK method having an initialization calculation step and a positioning calculation step using radio waves received from a plurality of satellites at a measurement point and a reference point,
A satellite selection step is executed before the initialization calculation step or between the initialization calculation step and the positioning calculation step to select a satellite to be used in a subsequent calculation, and the satellite selection step includes:
a step of excluding satellites other than the periodic satellites having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
Detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
for each said periodic satellite, comparing the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference of at least a predetermined value;
For a periodic satellite determined to have a difference of a predetermined value or more in CN ₀ , a step of acquiring a difference between CN ₀ at the same timing at a reference point and CN ₀ at a reference point one or more sidereal days ago that is the same as the measurement point;
For a periodic satellite determined to have a difference in _CN0 of a predetermined value or more, determining whether or not the difference in _CN0 is the same as the difference in _CN0 at a reference point;
and excluding, from among the periodic satellites determined to have a difference in _CN0 of a predetermined value or more, a periodic satellite whose difference in _CN0 is determined to be not the same as the difference in _CN0 at the reference point, as a satellite not to be used in subsequent calculations.
In any of the above methods, the satellite selection step comprises:
determining a range of directions to be excluded at the measurement point based on ambient environment information of the measurement point;
It is preferable that the method further comprises the step of excluding satellites that fall within the determined azimuth range as satellites that will not be used in subsequent calculations.
In any of the above-described methods, it is preferable that the initialization calculation step and the positioning calculation step are performed at regular time intervals.
In any one of the above methods, the positioning calculation step includes:
performing positioning calculations using radio waves at predetermined time intervals within a predetermined time range for all combinations including five or more periodic satellites among the periodic satellites to be used;
A step of calculating a displacement amount, which is a difference from one sidereal day ago, for the positioning calculation result for each of the combinations for each time interval, and calculating an average of the displacement amounts within the time range;
determining whether or not the majority of combinations have a displacement amount equal to or greater than a threshold;
It is preferable to further include a step of determining that there is no displacement when the number of combinations in which the displacement amount is equal to or greater than the threshold is not the majority or more.
In any of the above methods, when the majority or more of the combinations have a displacement amount equal to or greater than the threshold, further determining whether or not only a combination including a specific periodic satellite exceeds the threshold;
It is preferable to have a step of determining that there is a displacement if only the combination including a specific periodic satellite does not exceed the threshold.
An embodiment of a positioning device using satellites according to the present invention is a positioning device having an initialization calculation unit that performs initialization calculations to perform positioning of a measurement point by the RTK method using radio waves received from a plurality of satellites at a measurement point and a reference point, and a positioning calculation unit that performs positioning calculations,
A satellite selection unit is provided for selecting a satellite to be used in a subsequent calculation before an initialization calculation or between the initialization calculation and the positioning calculation, the satellite selection unit being:
a means for excluding satellites other than a periodic satellite having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
A means for detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
means for comparing, for each of said periodic satellites, the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference between the detected CN0 and the stored CN0 by more than a predetermined value;
and means for excluding a periodic satellite determined to have a difference in _CN0 of a predetermined value or more as a satellite not to be used in subsequent calculations.
Another aspect of the satellite-based positioning device according to the present invention is a positioning device having an initialization calculation unit that performs initialization calculations to perform positioning of a measurement point by the RTK method using radio waves received from a plurality of satellites at a measurement point and a reference point, and a positioning calculation unit that performs positioning calculations,
A satellite selection unit is executed before the initialization operation or between the initialization operation and the positioning operation to select a satellite to be used in a subsequent operation, the satellite selection unit being:
a means for excluding satellites other than a periodic satellite having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
A means for detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
means for comparing, for each of said periodic satellites, the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference between the detected CN0 and the stored CN0 by more than a predetermined value;
For a periodic satellite determined to have a difference of a predetermined value or more in CN ₀ , a means for acquiring a difference between CN ₀ at the same timing at a reference point and CN ₀ at a reference point one or more sidereal days ago that is the same as the measurement point;
A means for determining whether or not the difference in _CN0 of a periodic satellite determined to have a difference of _a predetermined value or more is the same as the difference in _CN0 at a reference point;
and a means for excluding, from among the periodic satellites determined to have a difference in _CN0 of a predetermined value or more, a periodic satellite whose difference in _CN0 is determined to be not the same as the difference in _CN0 at the reference point, as a satellite not to be used in subsequent calculations.
In any of the above-mentioned device aspects, the satellite selection unit
A means for determining a range of directions to be excluded at the measurement point based on ambient environment information of the measurement point;
It is preferable that the satellite detection apparatus further comprises a means for excluding satellites included in the determined azimuth range as satellites not to be used in subsequent calculations.
In any of the above aspects of the device, a means for waking up at a constant time interval in order to perform the initialization calculation and the positioning calculation;
It is preferable that the device further comprises a means for executing a series of processes including the initialization calculation and the positioning calculation after waking up, and going into a sleep state after completion of the processes.

According to the present invention, in a positioning method and a positioning device using GNSS, it is possible to efficiently identify satellites to be excluded from among the satellites used in calculations using the RTK method.

FIG. 1 is a diagram showing an example of a configuration of an overall positioning system including a positioning device according to a first embodiment of the present invention. FIG. 2 is a flow diagram illustrating an example of a positioning method according to the first embodiment. FIG. 3 is a continuation of the flow chart of FIG. FIG. 4 is a flow diagram that illustrates a schematic modification of the positioning method shown in FIGS. FIG. 5 is a diagram showing an example of a configuration of an overall positioning system including a positioning device according to the second embodiment of the present invention. FIG. 6 is a flow diagram illustrating an example of a positioning method according to the second embodiment. FIG. 7 is a diagram showing an example of a configuration of an overall positioning system including a positioning device according to the third embodiment of the present invention. FIG. 8 is a flow diagram illustrating an example of a positioning method according to the third embodiment. FIG. 9 is a diagram showing an example of a configuration of an overall positioning system including a positioning device according to the fourth embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings showing examples. In the drawings, the same or similar components in each embodiment are given the same reference numerals.

The RTK method, which is one of the positioning methods, consists of a two-step calculation process: an initialization calculation step that determines an integer bias corresponding to the path difference between the radio waves received at the measurement point and the radio waves received at a reference point (known point), and then a positioning calculation step that measures the position of the measurement point.

(1) First embodiment Fig. 1 is a schematic diagram showing an example of an overall positioning system including a positioning device according to a first embodiment of the present invention. A mobile station system 1 provided at a measurement point has an antenna 10, a receiving device 20, and a mobile station terminal 30. Here, the mobile station terminal 30 corresponds to the positioning device of the present invention.

The antenna 10 in the mobile station system 1 is installed at the measurement point. The antenna 10, for example, has a built-in high-frequency amplifier, receives radio waves (carrier waves) from multiple satellites S1, S2, etc. at the measurement point, amplifies the waves, and then transmits them to the receiving device 20 connected to the antenna 10. The receiving device 20 is composed of, for example, a high-frequency amplifier circuit, a code demodulation circuit, a digital signal processing circuit, etc., and adds predetermined additional data to the received radio waves and transmits them to the mobile station terminal 30. As an example, the receiving device 20 can be incorporated into the mobile terminal 30 to form an integrated device.

The mobile station terminal 30 is equipped with a central processing unit 31. Although not shown, the central processing unit 31 has a CPU and memory such as RAM, and the CPU loads and executes a specific application into the memory to perform calculation processing that realizes each function of the positioning device of the present invention. The central processing unit 31 has, as its main functional processing units, a satellite selection unit 1A, an initialization calculation unit 1B, a positioning calculation unit 1C, and a displacement determination unit 1D.

The satellite selection unit 1A has a function of appropriately selecting a satellite to be used for subsequent calculations in the initialization calculation unit 1B and the positioning calculation unit 1C. The initialization calculation unit 1B has a function of performing initialization calculations using radio waves from the satellite to be used to obtain a fix solution. The positioning calculation unit 1C has a function of calculating the position coordinates of the measurement point using radio waves from the satellite to be used. The displacement determination unit 1D has a function of determining whether or not the position of the measurement point has been displaced. Details of each functional processing unit will be described below with reference to Figures 2 and 3, along with the positioning method.

The mobile station terminal 30 further includes a communication device 32, preferably equipped with wireless communication capabilities, a display device 33 for displaying the processing status and processing results, and a storage device 34 for storing various data such as received radio waves and calculation result data. Each of these devices 32, 33, and 34 is also controlled by the central processing unit 31.

The mobile station terminal 30 can be implemented as a dedicated device incorporating only the functions of the present invention. However, it can also be implemented by installing a specific application on, for example, a personal computer, a tablet computer, a smartphone, etc. It is preferable that the mobile station terminal 30 is easily portable by the user.

On the other hand, the reference station system 5 installed at the reference point has an antenna 51, a receiving device 52, and a communication device 53.

An antenna 51 at the reference point is installed at a reference point whose position coordinates are already known. The antenna 51 also has a built-in high-frequency amplifier, for example, and receives radio waves (carrier waves) from multiple satellites S1, S2, etc. at the reference point, amplifies the waves, and then transmits them to a receiving device 52 connected to the antenna 51. The receiving device 52 has a configuration similar to that of the receiving device 20, and adds predetermined data to the received radio waves and transmits them to a communication device 53. The communication device 53 at the reference point and the communication device 32 of the mobile station terminal 30 at the measurement point are connected to each other, for example, via a wireless communication network, so that data can be transmitted, and the radio waves at the reference point can be transmitted to the mobile station terminal 30 in real time.

2 and 3 are flow charts each showing an outline of an example of the positioning method according to the first embodiment.
In step 101, the mobile station terminal 30 is woken up. When the mobile station terminal 30 is used for monitoring slope collapse, etc., it is often difficult to secure a power source, so it is preferable that the mobile station terminal 30 uses a battery as a power source. Therefore, in order to suppress power consumption, it is preferable that the mobile station terminal 30 performs positioning intermittently, not continuously. The mobile station terminal 30 is woken up, for example, every 30 minutes, and is put into a sleep state after completing a series of positioning procedures. In the sleep state, only the control function for waking up is operated, and other functions are stopped. In the case of monitoring slope collapse, it is preferable that the wake-up interval is every 60 minutes. It is preferable that the series of positioning procedures using the RTK method are initialized within 1 minute, and the subsequent positioning measurement is completed within 3 minutes. Note that the wake-up interval is not limited to every 60 minutes, and can be set to a fixed time interval, such as every 30 minutes, as necessary. If there is no problem with the power supply, it is also possible to perform positioning continuously. Although not shown, it is also possible to wake up the mobile station terminal 30 from a remote terminal that can communicate with the mobile station terminal 30 via a communication network. It is also possible to set and change the wake-up interval by transmitting a control signal from such a remote terminal to the mobile station terminal 30.

After waking up, the mobile station terminal 30 starts receiving radio waves from all satellites that the antenna 10 receives at that timing, and also starts receiving radio waves transmitted from the reference station system 5. The radio waves from the reference station system 5 are received by the antenna 51 from all the same satellites at the same timing. Note that the term "timing" in this specification means a point in time during a satellite cycle.

The processing of steps 102 to 105 is performed by the satellite selection unit 1A. The satellite selection unit 1A performs this in order to eliminate satellites whose radio waves should not be used in the subsequent initialization calculations and positioning calculations. This is performed before the initialization calculation steps of steps 106 and 107. Radio waves that should not be used are radio waves with a lot of noise and poor quality. Such radio waves can cause delays or inability to complete initialization, missed fixes, and reduced position accuracy.

In step 102, satellites other than a number of satellites that are periodic every sidereal day (hereinafter referred to as "periodic satellites") are excluded as satellites that will not be used in subsequent calculations. A periodic satellite is a satellite that is in the same position at the same time during each sidereal day cycle. In the positioning method of the present invention, the RTK method is applied using only periodic satellites.

GNSS satellites such as GPS and QZSS are located at the same position every sidereal day. Geostationary satellites (SBAS, Quasi-Zenith Satellite 3, BeiDou GEO, etc.) are also considered to be periodic satellites because they are always located at the same position. If an antenna is located at the same position at the same timing during the period one sidereal day ago, the same situation regarding the influence of multipath and obstacles on radio waves from these satellites should be reproduced. Therefore, each time radio waves are acquired, the radio waves can be compared with the radio waves received at the timing, for example, one sidereal day ago, to identify satellites whose conditions have changed. As another example, multiple sidereal days ago can be used instead of one sidereal day ago. For example, two sidereal days ago, seven sidereal days ago, etc. Alternatively, radio waves can be received and stored for one consecutive sidereal day at the beginning of installing a mobile station at a measurement point, and radio waves at the same timing among the continuous data of the stored radio waves can be used as a comparison standard. In the following, in this example, a comparison with radio waves one sidereal day ago will be described. Here, the carrier power to noise power density ratio _CN0 represents the strength of radio waves from a satellite, and changes when there is a change in the multipath due to the movement of obstacles or when radio waves are blocked. In the present invention, _CN0 is used as an evaluation parameter for the influence on radio waves.

In step 103, CN ₀ is detected based on the radio waves of each periodic satellite. Then, the detected CN ₀ is stored in the storage device 34 in association with the timing at which the radio waves were received. CN ₀ is defined as follows.
_CN0 = C/ _N0
C: Carrier power
N ₀ : Noise power density
Unit: dBHz

In step 104, the CN ₀ of each periodic satellite detected in step 103 is compared with the CN ₀ of the corresponding periodic satellite one sidereal day ago. The CN ₀ of one sidereal day ago is stored in the storage device 34. By the comparison, it is determined whether there is a difference between the two that is equal to or greater than a predetermined value, for example, whether there is a difference of 1 dBHz or more. If there is no difference that is equal to or greater than the predetermined value, the process proceeds directly to the initialization calculation.

If there is a difference of a predetermined value or more in _CN0 in step 104, that periodic satellite is excluded as a satellite that will not be used in the subsequent calculations, and the process proceeds to initialization calculations using the radio waves of the remaining periodic satellites.

By selecting satellites using the difference in CN ₀ before and after one sidereal day as an evaluation parameter, available periodic satellites can be selected before the initialization calculation. This makes it possible to avoid misfixes in the initialization calculation and shorten the initialization time. Furthermore, by eliminating satellites that cause accuracy degradation, it is possible to suppress in advance the variation in the positioning calculation results thereafter. By performing positioning using satellites whose CN ₀ has not changed since one sidereal day ago, the position of the antenna 10 and the displaced distance can be measured with high accuracy.

The processes of steps 106 and 107 are performed by the initialization calculation unit 1B. In step 106, the initialization calculation is performed using radio waves from all periodic satellites to be used that are selected by the satellite selection unit 1A. In step 107, a fix solution is obtained in the RTK method. If the mobile station terminal 30 wakes up every 30 minutes, it is preferable to obtain a fix solution within one minute in the initialization calculation. When an accuracy of several centimeters is achieved after initialization, the next step of positioning measurement is performed.

Steps 108 and 109 are performed by the positioning calculation unit 1C. In steps 108 and 109, positioning measurements are performed at the measurement point. In step 108, radio waves (herein referred to as "measurement data") from all periodic satellites to be used that have been selected by the satellite selection unit 1A (i.e., used in the initialization calculation) are acquired. For example, measurement data is acquired every second, and measurements are performed for three minutes. When n periodic satellites are used, n pieces of measurement data are obtained every second, and n x 180 pieces of measurement data are obtained in three minutes. The measurement data is stored in the storage device 34 in association with the timing at which the radio waves were received.

In step 109, a positioning calculation is performed using the measurement data obtained in step 108 to calculate the position coordinates. Preferably, when n periodic satellites are used, the positioning calculation is performed for all combinations of 5 or more. The total number of combinations of 5 or more is nCk (k is a natural number between 5 and n). As a result, position coordinates are obtained for each combination every second for 3 minutes. The position coordinates obtained at this stage are stored in the storage device 34 as provisional position coordinates of the measurement point.

Steps 110 to 117 in FIG. 3 are performed by the displacement determination unit 1D. In steps 110 to 117, the displacement at the measurement point from one sidereal day ago is determined. In step 110, for each combination of satellites, the difference between the position coordinates for each second and the position coordinates at the same time during the period one sidereal day ago, i.e., the amount of displacement, is calculated. In other words, the difference from the position coordinates for the same combination of satellites one sidereal day ago is derived. By using the same combination of satellites, it is possible to remove the effects of multipath and extract only the displacement. In step 111, the average amount of displacement for each combination for each second over a three-minute period is calculated.

In step 112, the amount of displacement for each of all combinations is compared with a threshold value (e.g., 3 mm) to determine whether or not the majority of combinations have a displacement amount that exceeds the threshold value. If the majority of combinations do not have a displacement amount that exceeds the threshold value, in step 113, it is determined that there is "no displacement," and the position coordinates of the measurement points are determined by calculating the temporal average over three minutes and the average of all combinations from the provisional position coordinates of each combination obtained in step 109 above.

On the other hand, if the majority of combinations have a displacement amount exceeding the threshold in step 112, then in step 114 it is determined whether only combinations including a specific satellite exceed the threshold. If only combinations including a specific satellite exceed the threshold, it is determined that the specific satellite is an unsuitable satellite for use in positioning, and in step 115 the combinations including the specific satellite are eliminated. Then, in step 116 it is determined again whether the majority of combinations have a displacement amount exceeding the threshold.

In step 116, if the majority of combinations have a displacement amount exceeding the threshold, it is determined in step 117 that "displacement exists." Then, from the provisional position coordinates of each combination obtained in step 109, the position coordinates of the measurement points are determined using only the combinations remaining at this stage, and the displacement amount of the measurement points is also determined.

If in step 114 only the combination including a specific satellite does not exceed the threshold, then in step 117 it is determined that "displacement exists" and the position coordinates and amount of displacement of the measurement point are determined.

If the majority of combinations do not have a displacement amount exceeding the threshold in step 116, then in step 113 it is determined that there is no displacement and the position coordinates of the measurement point are determined.

After the position coordinates of the measurement point are determined, or the position coordinates of the measurement point and the amount of displacement are determined, the mobile station terminal 30 is put into a sleep state.

FIG. 4 is a flow diagram that shows a schematic modification of the positioning method shown in FIG. 2 and FIG. 3. Only the points different from the flow diagrams of FIG. 2 and FIG. 3 will be described. In the positioning method of FIG. 4, the processes by the satellite selection unit 1A and the initialization calculation unit 1B of FIG. 1 are performed in the reverse order to the positioning method of FIG. 2. That is, in steps 401 and 402, first, an initialization calculation is performed using radio waves of all received satellites to obtain a fix solution of RTK. Then, in steps 403 to 406, satellite selection is performed with CN ₀ as an evaluation parameter, as in steps 102 to 105 of FIG. 2. The subsequent processes by the positioning calculation unit 1C and the displacement determination unit 1D are the same as those in FIG. 2 and FIG. 3.

In the modified positioning method of FIG. 4, satellite selection is performed between the initialization calculation step and the positioning calculation step, so that a periodic satellite that can be used for the subsequent positioning calculation can be selected before the positioning calculation step. This makes it possible to suppress in advance the variation in the results of the subsequent positioning calculation.

Although not shown, the positioning method of the present invention can further be combined with the conventional techniques of excluding inappropriate satellites using an elevation mask, a _CN0 mask, selection of a satellite system, selection of a positioning start timing, etc. (The same applies to the following embodiments.) These conventional techniques are executed based on the calculation status and calculation results after the start or completion of the initialization calculation step or the positioning calculation step.

(2) Second embodiment Fig. 5 is a schematic diagram showing an example of an overall positioning system including a positioning device according to a second embodiment of the present invention. A mobile station system 1 provided at a measurement point has an antenna 10, a receiving device 20, and a mobile station terminal 30. Again, the mobile station terminal 30 corresponds to the positioning device of the present invention. The configuration of the mobile station system 1 is almost the same as that of the first embodiment described above, so a description thereof will be omitted. In the second embodiment, the processing in the satellite selection unit 1A of the central processing unit 31 is different from that of the first embodiment, but this will be described together with the positioning method with reference to Fig. 6.

On the other hand, the reference station system 5 installed at the reference point has an antenna 51, a receiving device 52, and a reference station terminal 60.

The antenna 51 and the receiving device 52 at the reference point are the same as those in the first embodiment, so a description is omitted. However, the receiving device 52 transmits the received radio waves to the reference station terminal 60.

The reference station terminal 60 comprises a central processing unit 61, a storage device 62, and a communication device 63. The central processing unit 61 has a CPU and memory such as RAM, not shown, and the CPU loads a predetermined application into the memory and executes it to realize each functional processing unit of a _CN0 detection unit 6A and a _CN0 recording unit 6B. The _CN0 detection unit 6A detects the _CN0 of the radio waves of each satellite at the reference point received from the receiving device 52. The _CN0 recording unit 6B stores the _CN0 detected for each satellite in the storage device 62 in association with the timing of receiving the radio waves.

The communication device 63 of the reference station terminal 60 transmits radio waves at the reference point to the communication device 32 of the mobile station terminal 30 under the control of the central processing unit 61. At that time, the communication device 63 transmits the CN ₀ of the radio waves and, for example, the CN ₀ of the radio waves one sidereal day ago together with the radio waves. Note that, as explained in the first embodiment, the CN ₀ of one sidereal day ago is only an example, and the CN ₀ of several sidereal days ago may be used.

As another example, the central processing unit 61 may be configured to detect the CN ₀ of a radio wave, calculate the difference between that radio wave and the CN ₀ at the same timing one sidereal day earlier, and transmit the calculated difference in CN ₀ from the communication device 63 to the communication device 32 of the mobile station terminal 30.

The reference station terminal 60 can be implemented as a dedicated device incorporating only the above functions. However, it can also be implemented by installing a specific application on, for example, a personal computer, tablet computer, smartphone, etc.

Figure 6 is a flow diagram that shows an example of a positioning method in the second embodiment. Figure 6 mainly shows the parts that are different from the first embodiment. Wake-up is similar to step 101 in Figure 2.

The processing of steps 601 to 606 is performed by the satellite selection unit 1A, which excludes satellites whose radio waves should not be used in subsequent initialization and positioning calculations.

In step 601, satellites other than periodic satellites are excluded as satellites that will not be used in the subsequent calculations. This step is the same as step 102 in Fig. 2. In step 602, _CN0 is detected based on the radio waves of each periodic satellite, and stored in storage device 34 in association with the timing of receiving the radio waves. This step is the same as step 103 in Fig. 2.

In step 603, the CN ₀ of each periodic satellite detected in step 602 is compared with the CN ₀ of the corresponding periodic satellite one sidereal day ago. The CN ₀ of one sidereal day ago is stored in the storage device 34. By the comparison, it is determined whether there is a difference between the two of a predetermined value or more, for example, a difference of 1 dBHz or more. If there is no difference of the predetermined value or more, the process proceeds directly to the initialization calculation.

If there is a difference in CN ₀ of a predetermined value or more in step 603, the CN ₀ of the periodic satellite at the reference point is acquired in step 604. The CN ₀ at the reference point acquired here is the CN ₀ at the same timing as the measurement point and the CN ₀ one sidereal day before. These CN ₀ data are transmitted from the communication device 63 of the reference station terminal 60 to the communication device 32 of the mobile station terminal 30. The satellite selection unit 1A calculates the difference between the CN ₀ at the same timing at the received reference point and the CN ₀ one sidereal day before. As another example, the difference between the CN ₀ at the same timing at the reference point and the CN ₀ one sidereal day before may be calculated in the reference station terminal 60, and the data of the difference in CN ₀ may be transmitted to the mobile station terminal 30.

In step 605, the difference in CN ₀ at the measurement point is compared with the difference in CN ₀ at the reference point to determine whether they are the same. "The same" includes cases where they are completely the same, as well as cases where there is a tolerable difference but they are substantially the same. CN ₀ is affected not only by changes in the surrounding environment such as obstacles, but also by changes in meteorological conditions such as rain and snow. This change in meteorological conditions affects CN ₀ of many satellites, so it is difficult to distinguish it from the effect of changes in the surrounding environment of the measurement point. In this case, the effect of CN ₀ due to changes in meteorological conditions is also seen at the reference point (assuming that the meteorological conditions are the same as those of the measurement point and the reference point). Therefore, in step 605, if the difference in CN ₀ at the measurement point is the same as the difference in CN ₀ at the reference point, it is determined that the difference in CN ₀ at the measurement point is due to meteorological conditions (is normal), and the initialization calculation is started.

In step 605, if the difference in _CN0 at the measurement point is not the same as the difference in _CN0 at the reference point, it is determined that the difference is due to factors other than meteorological conditions (changes in the surrounding environment of the measurement point due to obstacles, etc.), and the periodic satellite is excluded as a satellite that will not be used in subsequent calculations. Then, the initialization calculation is performed using the radio waves of the remaining periodic satellites.

In the first embodiment described above, the evaluation criterion is only the difference in CN ₀ at the measurement point before and after one or more sidereal days, so that satellites that do not need to be excluded may be excluded. In the second embodiment, by comparing the difference in CN ₀ at both the measurement point and the reference point before and after one or more sidereal days, it is possible to distinguish the influence of meteorological conditions on CN ₀ from the influence of changes in the surrounding environment at the measurement point. As a result, it is possible to avoid excluding satellites that do not need to be excluded.

The subsequent initialization calculation by the initialization calculation unit 1B is similar to steps 106 and 107 in FIG. 2 in the first embodiment. Further, the subsequent processing by the positioning calculation unit 1C and the displacement determination unit 1D is similar to step 108 and subsequent steps in FIG. 2 in the first embodiment.

As a modification of the second embodiment, the order of the processing by the satellite selection unit 1A and the processing by the initialization calculation unit 1B may be reversed, as in FIG. 4 shown as a modification of the first embodiment described above.

(3) Third embodiment Fig. 7 is a schematic diagram showing an example of an overall positioning system including a positioning device according to a third embodiment of the present invention. A mobile station system 1 provided at a measurement point has an antenna 10, a receiving device 20, a mobile station terminal 30, and a surrounding environment monitoring device 40. Again, the mobile station terminal 30 corresponds to the positioning device of the present invention. The reference station system 5 is the same as that of the first embodiment.

The third embodiment differs from the first embodiment in that the mobile station system 1 has an ambient environment monitoring device 40. In relation to this, the third embodiment differs from the first embodiment in the processing in the satellite selection unit 1A of the central processing unit 31, which will be described together with the positioning method with reference to FIG. 8.

The surrounding environment monitoring device 40 is, for example, a video camera, a sensor that detects objects, etc. The surrounding environment monitoring device 40 monitors, for example, the presence or absence of obstacles such as people and cars around the measurement point. Then, when there is a change in the surrounding environment, for example when it detects the appearance of a new obstacle or the disappearance of an existing obstacle, it generates surrounding environment information including the position information of the obstacle (azimuth range, height, etc. as seen from the antenna 10) and timing.

The surrounding environment monitoring device 40 is connected to the mobile station terminal 30 so as to be able to communicate with it via wired or wireless communication. The surrounding environment monitoring device 40 communicates surrounding environment information to the mobile station terminal 30 when there is a change in the surrounding environment. The mobile station terminal 30 stores the received surrounding environment information in the storage device 34. As an example, if the mobile station terminal 30 wakes up every 30 minutes, the mobile station terminal 30 may communicate with the surrounding environment monitoring device 40 when it wakes up to obtain and store new surrounding environment information.

Figure 8 is a flow diagram that shows an example of a positioning method according to the third embodiment. Figure 8 mainly shows the parts that are different from the first embodiment. Wake-up is similar to step 101 in Figure 2.

The processing of steps 801 to 807 is performed by the satellite selection unit 1A, which excludes satellites whose radio waves should not be used in subsequent initialization and positioning calculations.

In step 801, surrounding environment information is received. In step 802, if the presence of a new obstacle is confirmed from the received surrounding environment information, the direction range in which radio waves are expected to be unable to be received normally due to the obstacle is determined as a direction range to be excluded. The determined direction range to be excluded is stored in the storage device 34. Then, in step 803, satellites that fall within the direction range to be excluded are excluded as satellites that will not be used in subsequent calculations.

Steps 804 to 807 are similar to steps 102 to 105 in FIG. 2 in the first embodiment. As another example, steps 601 to 606 in FIG. 6 in the second embodiment may be performed instead of steps 804 to 807. The subsequent initialization calculation by the initialization calculation unit 1B is also similar to steps 106 and 107 in FIG. 2. Furthermore, the subsequent processing by the positioning calculation unit 1C and the displacement determination unit 1D is also similar to step 108 and subsequent steps in FIG. 2.

As a modification of the third embodiment, similar to FIG. 4 shown as a modification of the first embodiment described above, the order of the processing by the satellite selection unit 1A and the processing by the initialization calculation unit 1B may be reversed.

(4) Fourth embodiment Fig. 9 is a schematic diagram showing an example of the overall positioning system including a positioning device according to a fourth embodiment of the present invention. A mobile station system 1 provided at a measurement point has an antenna 10, a receiving device 20, and a mobile station terminal 30. On the other hand, a reference station system 5 provided at a reference point has an antenna 51, a receiving device 52, and a reference station terminal 60. In the fourth embodiment, the mobile station terminal 30 and the reference station terminal 60 each have at least a communication device 32, 63, and transmit radio waves received from a satellite to a remote computing device 70 via an appropriate communication network. In the fourth embodiment, the remote computing device 70 corresponds to the positioning device of the present invention. The remote computing device 70 is, for example, a computer with a predetermined application installed, and can be installed at any location.

The remote computing device 70 includes a central processing unit 71. Although not shown, the central processing unit 71 has a CPU and a memory such as a RAM, and the CPU loads and executes a predetermined application into the memory to perform computational processing to realize each function of the positioning device of the present invention. The central processing unit 71 has a satellite selection unit 1A, an initialization computation unit 1B, a positioning computation unit 1C, and a displacement determination unit 1D as main functional processing units. The central processing unit 71 can perform the same processing (see Figures 2 to 4, 6, and 8) as the central processing unit 31 of the mobile station terminal 30 in the first, second, or third embodiment described above, based on the radio waves received from the mobile station terminal 30 and the reference station terminal 30. That is, in the fourth embodiment, each of the processes of satellite selection, initialization computation, positioning computation, and displacement determination is performed by the remote computing device 70. In that case, the communication device 72, the display device 73, and the storage device 74 can function in the same way as the communication device 32, the display device 33, and the storage device 34 of the mobile station terminal 30 in the first, second, or third embodiment.

When the central processing unit 71 performs processing similar to that of the central processing unit 31 of the second embodiment (see Figures 5 and 6), the detection of _CN0 of the radio waves of each satellite at the reference point may be performed by the central processing unit 71 based on the radio waves received from the reference station terminal 60, or, as in the second embodiment, the detection of _CN0 of the radio waves at the reference point may be performed in the reference station terminal 60 and the result transmitted to the remote computing device 70.

As a variation of the fourth embodiment, the remote computing device 70 may execute only some of the processes of satellite selection, initialization calculation, positioning calculation, and displacement determination, rather than all of them. For example, the satellite selection process may be performed by the mobile station terminal 30, which may transmit only radio waves from the selected satellite to the remote computing device 70, and the remote computing device 70 may execute the processes from the initialization calculation onwards.

Although each embodiment of the present invention has been described above with reference to one configuration example, the embodiments of the present invention are not limited to the above-mentioned examples, and various modifications are possible without departing from the spirit of the present invention, and such modifications are also included in the scope of the present invention.

REFERENCE SIGNS LIST 1 Mobile station system 10 Antenna 20 Receiving device 30 Mobile station terminal 31 Central processing unit 32 Communication device 33 Display device 34 Storage device 40 Surrounding environment monitoring device 5 Reference station system 51 Antenna 52 Receiving device 53 Communication device 60 Reference station terminal 61 Central processing unit 62 Storage device 63 Communication device

Claims (10)

A positioning method for measuring the position of a measurement point by an RTK method, the method having an initialization calculation step and a positioning calculation step, using radio waves received from a plurality of satellites at a measurement point and a reference point,
A satellite selection step is executed before the initialization calculation step or between the initialization calculation step and the positioning calculation step to select a satellite to be used in a subsequent calculation, and the satellite selection step includes:
a step of excluding satellites other than the periodic satellites having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
Detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
for each said periodic satellite, comparing the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference of at least a predetermined value;
and excluding a periodic satellite determined to have a difference in _CN0 of a predetermined value or more as a satellite not to be used in subsequent calculations. A positioning method for measuring the position of a measurement point by an RTK method, the method having an initialization calculation step and a positioning calculation step, using radio waves received from a plurality of satellites at a measurement point and a reference point,
A satellite selection step is executed before the initialization calculation step or between the initialization calculation step and the positioning calculation step to select a satellite to be used in a subsequent calculation, and the satellite selection step includes:
a step of excluding satellites other than the periodic satellites having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
Detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
for each said periodic satellite, comparing the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference of at least a predetermined value;
For a periodic satellite determined to have a difference of a predetermined value or more in CN ₀ , a step of acquiring a difference between CN ₀ at the same timing at a reference point and CN ₀ at a reference point one or more sidereal days ago that is the same as the measurement point;
For a periodic satellite determined to have a difference in _CN0 of a predetermined value or more, determining whether or not the difference in _CN0 is the same as the difference in _CN0 at a reference point;
and excluding, from among the periodic satellites determined to have a difference in _CN0 of a predetermined value or more, a periodic satellite whose difference in _CN0 is determined to be not the same as the difference in _CN0 at a reference point, as a satellite not to be used in subsequent calculations. The satellite selection step includes:
determining a range of directions to be excluded at the measurement point based on ambient environment information of the measurement point;
3. The method of claim 1, further comprising the step of excluding satellites that fall within the determined azimuth range as satellites that will not be used in subsequent calculations. The satellite-based positioning method according to any one of claims 1 to 3, characterized in that the initialization calculation step and the positioning calculation step are performed at regular time intervals. The positioning calculation step includes:
performing positioning calculations using radio waves at predetermined time intervals within a predetermined time range for all combinations including five or more periodic satellites among the periodic satellites to be used;
calculating a displacement amount, which is a difference from one sidereal day ago, for the positioning calculation result for each of the combinations for each time interval, and calculating an average of the displacement amounts within the time range;
determining whether or not the majority of combinations have a displacement amount equal to or greater than a threshold;
5. The method of claim 1, further comprising a step of determining that there is no displacement when the majority of the combinations do not have a displacement amount equal to or greater than the threshold value. If the majority or more of the combinations have a displacement amount equal to or greater than the threshold, a further step of determining whether or not only a combination including a specific periodic satellite exceeds the threshold;
The method for positioning using satellites according to claim 5, further comprising a step of determining that there is displacement when only a combination including a specific periodic satellite does not exceed the threshold value. A positioning device having an initialization calculation unit that performs initialization calculations to perform positioning of a measurement point by an RTK method using radio waves received from a plurality of satellites at a measurement point and a reference point, and a positioning calculation unit that performs positioning calculations,
A satellite selection unit is provided for selecting a satellite to be used in a subsequent calculation before an initialization calculation or between the initialization calculation and the positioning calculation, the satellite selection unit being:
a means for excluding satellites other than a periodic satellite having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
A means for detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
means for comparing, for each of said periodic satellites, the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference between the detected CN0 and the stored CN0 by more than a predetermined value;
means for excluding a periodic satellite determined to have a difference in _CN0 of a predetermined value or more as a satellite not to be used in subsequent calculations. A positioning device having an initialization calculation unit that performs initialization calculations to perform positioning of a measurement point by an RTK method using radio waves received from a plurality of satellites at a measurement point and a reference point, and a positioning calculation unit that performs positioning calculations,
A satellite selection unit is executed before the initialization operation or between the initialization operation and the positioning operation to select a satellite to be used in a subsequent operation, the satellite selection unit being:
a means for excluding satellites other than a periodic satellite having a periodicity every sidereal day as satellites not to be used in subsequent calculations;
A means for detecting and storing a carrier power to noise power density ratio (CN0 ₎ of radio waves at a measurement point for each of the periodic satellites;
means for comparing, for each of said periodic satellites, the detected _CN0 with a stored _CN0 from one or more sidereal days ago to determine whether there is a difference between the detected CN0 and the stored CN0 by more than a predetermined value;
For a periodic satellite determined to have a difference of a predetermined value or more in CN ₀ , a means for acquiring a difference between CN ₀ at the same timing at a reference point and CN ₀ at a reference point one or more sidereal days ago that is the same as the measurement point;
A means for determining whether or not the difference in _CN0 of a periodic satellite determined to have a difference of _a predetermined value or more is the same as the difference in _CN0 at a reference point;
and a means for excluding, from among periodic satellites determined to have a difference in _CN0 of a predetermined value or more, a periodic satellite whose difference in _CN0 is determined to be not the same as the difference in _CN0 at a reference point, as a satellite not to be used in subsequent calculations. The satellite selection unit:
A means for determining a range of directions to be excluded at the measurement point based on ambient environment information of the measurement point;
9. The satellite-based positioning device according to claim 7, further comprising: means for excluding satellites included in the determined azimuth range as satellites not to be used in subsequent calculations. a means for waking up at a constant time interval in order to perform the initialization calculation and the positioning calculation;
The satellite-based positioning device according to any one of claims 7 to 9, further comprising: a means for executing a series of processes including the initialization calculation and the positioning calculation after waking up, and going into a sleep state after completion of the processes.

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