Positioning system, positioning device, positioning method, and positioning program

Abstract

This system provides a positioning system for use between a reference station and a target station with a large ionospheric delay difference. [Solution] The positioning system comprises a reference station that receives a first positioning signal from an artificial satellite and a target station that receives a second positioning signal from the artificial satellite. The reference station generates an elevation-azimuth mask that includes information on the elevation angle and azimuth angle of the artificial satellite and determines whether or not to generate correction information, using the total number of ionospheric electrons based on a third positioning signal received from the artificial satellite by an evaluation station located near the target station and the total number of ionospheric electrons based on the first positioning signal. The reference station generates the correction information using the positioning error based on the first positioning signal, and the target station calculates position information based on the second positioning signal, the information, and the correction information corresponding to the elevation angle and azimuth angle.

Description

Technical Field

[0001] The present disclosure relates to a positioning system, a positioning device, a positioning method, and a positioning program.

Background Art

[0002] Patent Document 1 describes a system that measures the distance between a base station (reference station) and a satellite at the base station (reference station) to obtain a measurement error corresponding to ionospheric delay and tropospheric delay, and corrects the position information of the base station (target station) to be corrected based on the correction information corresponding to the measurement error.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the system described in Patent Document 1, when performing positioning correction at the base station to be corrected using differential GPS (DGPS: Differential Global Positioning System), if the delay difference between the ionospheric delay at the base station (reference station) used for estimation and the ionospheric delay at the base station to be corrected (target station) is large, there is a problem that the positioning accuracy deteriorates.

[0005] The present disclosure aims to provide a positioning system that solves the above problems.

Means for Solving the Problems

[0006] According to one aspect of the present disclosure, a positioning system is provided comprising: a reference station that receives a first positioning signal from an artificial satellite; and a target station that receives a second positioning signal from the artificial satellite, wherein the reference station generates an elevation-azimuth mask that includes information on the elevation angle and azimuth angle of the artificial satellite and determines whether or not to generate correction information, using the total number of ionospheric electrons based on a third positioning signal received from the artificial satellite by an evaluation station located near the target station, and the total number of ionospheric electrons based on the first positioning signal; the reference station generates the correction information using the positioning error based on the first positioning signal; and the target station calculates position information based on the second positioning signal, the information, and the correction information corresponding to the elevation angle and azimuth angle.

[0007] According to one aspect of the present disclosure, a positioning device is provided, comprising: an acquisition means for acquiring an elevation angle and azimuth mask including correction information and information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite; a receiving means for receiving a second positioning signal from the artificial satellite and acquiring the elevation angle and azimuth angle between the artificial satellite and the positioning device; and a positioning means for calculating position information based on the second positioning signal, the elevation angle and azimuth angle, the information of the elevation angle and azimuth mask corresponding to the elevation angle and azimuth angle, and the correction information corresponding to the elevation angle and azimuth angle, wherein the elevation angle and azimuth mask is generated by the reference station using the total number of ionospheric electrons based on a third positioning signal received from the artificial satellite by an evaluation station located near the positioning device and the total number of ionospheric electrons based on the first positioning signal, and the correction information is generated by the reference station using the positioning error based on the first positioning signal.

[0008] According to one aspect of the present disclosure, a positioning method is provided comprising: an acquisition step of acquiring an elevation angle-azimuth mask including correction information and information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite; a reception step of receiving a second positioning signal from the artificial satellite and acquiring the elevation angle and azimuth angle between the artificial satellite and the positioning device; and a positioning step of calculating position information based on the second positioning signal, the elevation angle and azimuth angle, the information of the elevation angle-azimuth mask corresponding to the elevation angle and azimuth angle, and the correction information corresponding to the elevation angle and azimuth angle, wherein the elevation angle-azimuth mask is generated by the reference station using the total number of ionospheric electrons based on a third positioning signal received from the artificial satellite by an evaluation station located near the positioning device and the total number of ionospheric electrons based on the first positioning signal, and the correction information is generated by the reference station using the positioning error based on the first positioning signal.

[0009] According to one aspect of the present disclosure, a positioning program is provided comprising: an acquisition step of acquiring an elevation-azimuth mask including correction information and information determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite; a reception step of receiving a second positioning signal from the artificial satellite and acquiring the elevation angle and azimuth angle between the artificial satellite and the positioning device; and a positioning step of calculating position information based on the second positioning signal, the elevation angle and azimuth angle, the information of the elevation-azimuth mask corresponding to the elevation angle and azimuth angle, and the correction information corresponding to the elevation angle and azimuth angle, wherein the elevation-azimuth mask is generated by the reference station using the total number of ionospheric electrons based on a third positioning signal received from the artificial satellite by an evaluation station located near the positioning device and the total number of ionospheric electrons based on the first positioning signal, and the correction information is generated by the reference station using the positioning error based on the first positioning signal. [Effects of the Invention]

[0010] According to the present disclosure, it becomes possible to provide a positioning system for use between a reference station and a target station with a large ionospheric delay difference. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing an example of a positioning system according to one embodiment of the present invention. [Figure 2] This block diagram shows the configuration of the target station according to one embodiment of the present disclosure. [Figure 3] This block diagram shows the configuration of a reference authority according to one embodiment of the present disclosure. [Figure 4] This is a block diagram showing the configuration of an evaluation bureau according to one embodiment of the present disclosure. [Figure 5] This is a block diagram showing the hardware configuration of an information processing device according to one embodiment of the present invention. [Figure 6] This is a schematic diagram showing the TEC difference between a reference station and an evaluation station according to one embodiment of the disclosure of this application. [Figure 7] This is a schematic diagram showing a method for generating an elevation angle and azimuth angle mask according to one embodiment of the disclosure of this application. [Figure 8] This is a sky plot showing an elevation and azimuth mask according to one embodiment of the disclosure of this application. [Figure 9] This flowchart shows an example of positioning processing for an evaluation station according to one embodiment of the disclosure of this application. [Figure 10] This flowchart shows an example of the process for generating an elevation angle and azimuth angle mask according to one embodiment of the present invention. [Figure 11] This flowchart shows an example of the process for generating correction information according to one embodiment of the present invention. [Figure 12] This flowchart shows an example of an evaluation process for an elevation angle and azimuth angle mask according to one embodiment of the present invention. [Figure 13] This flowchart shows an example of the positioning process for a target station according to one embodiment of the disclosure of this application. [Figure 14] This is a block diagram showing a positioning system according to one embodiment of the present invention. [Modes for carrying out the invention]

[0012] Hereinafter, a positioning system according to an embodiment of the present disclosure will be described with reference to the drawings. In all the drawings, the same or corresponding components are denoted by the same reference numerals, and common descriptions will be omitted.

[0013] [First Embodiment] FIG. 1 is a schematic diagram showing an example of a positioning system according to an embodiment of the present disclosure. The positioning system 1 is a positioning system using a global navigation satellite system (GNSS) including a global positioning system (GPS). The positioning system 1 includes a target station 2, a reference station 3, an evaluation station 4, and a control station 5. The target station 2, the reference station 3, the evaluation station 4, and the control station 5 may be communicably connected to each other via a network 8. It is desirable that the target station 2, the reference station 3, and the evaluation station 4 can receive a positioning signal 61 from the artificial satellite 6A. It is desirable that the target station 2, the reference station 3, the control station 5, and the artificial satellite 6B are communicably connected.

[0014] (Target Station 2) The target station 2 can be a base station or a base station system equipped with a GPS receiver. The target station 2 receives a positioning signal 61 from a plurality of artificial satellites 6A via the ionosphere 9 and measures the position of the target station 2. The target station 2 may be a fixed base station fixedly provided at an arbitrary position or a movable base station. When the target station 2 is a movable base station, the target station 2 can be, for example, a bicycle, a motorcycle, an automobile, a train, a ship, an aircraft, a running drone, a flying drone, or the like. Alternatively, the target station 2 may be an information processing device such as a mobile terminal. When a user holds a mobile terminal and boards a moving body such as a bicycle, a motorcycle, an automobile, a train, or a ship, the user or the moving body can be regarded as the target station 2.

[0015] (Reference Station 3) Reference station 3 may be a base station or base station system equipped with a GPS receiver. Reference station 3 receives positioning signals 61 from multiple artificial satellites 6A via the ionosphere 9 and measures its position. Here, the location where reference station 3 is installed is known, and reference station 3 calculates a positioning error using position information obtained by positioning based on the positioning signals 61 and the known position of reference station 3. Reference station 3 transmits the positioning error and correction information 62 based on the positioning error to target station 2. Hereinafter, this embodiment will be described assuming that the correction information 62 includes the positioning error calculated by reference station 3 and a correction value obtained using the positioning error. Note that the correction information 62 transmitted from reference station 3 to target station 2 may include the positioning error and correction value for one artificial satellite 6A, or it may include multiple positioning errors and multiple correction values ​​for multiple artificial satellites 6A. The correction value is obtained, for example, by calculating the difference between the distance (geometric distance) based on the difference between the true position of the reference station 3 and the true position of the satellite 6A, and the distance (pseudo-distance) based on the positioning signal 61. The reference station 3 can calculate the positioning error for each of the multiple satellites 6A and the reference station 3, and obtain the correction value.

[0016] Based on the assumption that the positioning error calculated at base station 3 is equal to the positioning error at target station 2, target station 2 can correct its position using correction information 62. That is, based on the positioning error at base station 3, target station 2 can perform positioning correction using differential GPS (DGPS). Positioning correction using DGPS based on correction information 62 may use known techniques. If the factors causing the positioning error at target station 2 and the factors causing the positioning error at base station 3 are the same, positioning correction using DGPS may improve the accuracy of positioning at target station 2. Positioning correction using DGPS may be effective against satellite orbit errors, satellite clock errors, ionospheric delay errors, tropospheric delay errors, etc.

[0017] (Ionosphere 9) The ionosphere 9 is a layer of the atmosphere located at an altitude of approximately 60 km to 500 km above the Earth's surface, and includes the D layer, the E layer, and the F layer (the F layer splits into the F1 and F2 layers during the day). The ionosphere 9 is formed by the ionization of Earth's atmospheric molecules and atoms by ultraviolet rays and X-rays from the sun. Therefore, the state of the ionosphere 9 during the day and the state of the ionosphere 9 at night are different from each other. The state of the ionosphere 9 in the daytime hemisphere of the Earth and the state of the ionosphere 9 in the nighttime hemisphere of the Earth are also different from each other. In other words, the ionosphere 9 can include multiple different states of the ionosphere. For example, the ionosphere 9 can include ionosphere 9A and ionosphere 9B. The propagation path characteristics of ionosphere 9A and ionosphere 9B can be different from each other.

[0018] Radio waves with frequencies from 30 MHz to 300 MHz (VHF: Very High Frequency) and frequencies from 300 MHz to 3 GHz (UHF: Ultra High Frequency) can penetrate the ionosphere 9, but their propagation speed decreases as they propagate through the ionosphere 9. Therefore, the delay amount of the signal received by the positioning signal 61 from the ionosphere 9A is different from the delay amount of the signal received by the positioning signal 61 from the ionosphere 9B. As a result, the difference between the propagation path characteristics of the ionosphere 9A and the propagation path characteristics of the ionosphere 9B can cause positioning errors using GPS.

[0019] Regarding positioning correction using DGPS, the positioning error calculated at base station 3 includes all errors such as satellite orbit error, satellite clock error, ionospheric delay error, and tropospheric delay error. For example, if the ionospheric delay error at target station 2 and the ionospheric delay error at base station 3 differ significantly, there may be a difference between the positioning error at target station 2 and the positioning error at base station 3. Therefore, even if target station 2 performs positioning correction using DGPS, the positioning accuracy at target station 2 will not improve.

[0020] Ionospheric delay error is related to the total electron content (TEC) of the ionosphere. For example, if the difference between the TEC of ionosphere 9A between satellite 6A and target station 2 and the TEC of ionosphere 9B between satellite 6A and reference station 3 (hereinafter referred to as the "TEC difference") becomes large, the ionospheric delay error will increase. Also, when ionospheric activity becomes more active in response to the space environment, such as solar activity, the variation in TEC from region to region increases. Periods of active ionospheric activity are called ionospheric disturbance periods, and periods of inactive ionospheric activity are called ionospheric quiescence periods. Positioning accuracy may deteriorate when using DGPS for positioning correction during ionospheric disturbance periods compared to when using DGPS for positioning correction during ionospheric quiescence periods.

[0021] (Evaluation Bureau 4) Evaluation Station 4 is a Global Navigation Satellite System (GNSS) continuous observation system installed by the Geospatial Information Authority of Japan and is located at a GNSS continuous observation point. When Evaluation Station 4 is a continuous observation system, it comprises an antenna for receiving positioning signals 61 from GNSS satellites, a receiver, wired communication equipment, and wireless communication equipment. It is desirable that Evaluation Station 4 is a GNSS continuous observation system located near the target station 2. It is also desirable that the location where Evaluation Station 4 is installed is known.

[0022] The evaluation station 4 may be a base station or base station system other than a GNSS continuous observation system. For example, the evaluation station 4 may be a base station installed by the user, and the evaluation station 4 may be a base station equipped with a GPS receiver. When the evaluation station 4 is installed by the user, the evaluation station 4 receives positioning signals 61 from multiple artificial satellites 6A via the ionosphere 9 and measures its position in advance. Furthermore, the evaluation station 4 stores the measured position information of the evaluation station 4 in a storage medium or the like. That is, it is desirable that the location where the evaluation station 4 is installed is known in advance by measurement. It is also desirable that the location where the evaluation station 4 is installed is in the vicinity of the target station 2. In the following, this embodiment will be described assuming that the location where the evaluation station 4 is installed is known or can be obtained with sufficient accuracy.

[0023] (Control station 5) The control station 5 is a base station or base station system capable of communicating with the satellite 6B, and the control station 5 is connected to the reference station 3 and the satellite 6B in a communicative manner. It receives correction information 62 from the reference station 3 and transmits the correction information 62 to the target station 2 via the satellite 6B. In Figure 1, the control station 5 transmits the correction information 62 to the target station 2 via the satellite 6B, but the control station 5 may also transmit the correction information 62 to the target station 2 via a network 8 or the like. In Figure 1, the control station 5 is provided separately from the reference station 3, but the reference station 3 may have the functions of the control station 5. Alternatively, the reference station 3 may directly transmit the correction information 62 to the target station 2. The configuration of the reference station 3, the control station 5, and the satellite 6B is not particularly limited as long as the correction information 62 can be transmitted from the reference station 3 to the target station 2. In the following, this embodiment will be described assuming that the reference station 3 has the functions of the control station 5.

[0024] (Artificial satellite 6A and artificial satellite 6B) Satellite 6A is a GPS satellite that transmits a positioning signal 61 obtained by spreading pseudorandom numbers across the spectrum. Satellite 6A is equipped with a high-precision atomic clock and uses the atomic clock to generate time information. The positioning signal 61 includes time information, orbital information, and information about satellite 6A. In Figure 1, one satellite 6A is shown, but there can be four or more satellites 6A in GPS positioning. Satellite 6B is a communications satellite. Satellite 6B can communicate wirelessly with target station 2, reference station 3, evaluation station 4, or control station 5 using microwave radio waves.

[0025] (Configuration of Target Station 2) Figure 2 is a block diagram showing the configuration of a target station 2 according to one embodiment of the present disclosure. The target station 2 comprises an information processing device 21, a receiving unit 22, a transmitting unit 23, and a communication unit 24. The information processing device 21 is a computer, and may be, for example, a personal computer, a workstation, a mobile terminal, a hardware server, a software server, etc. If the information processing device 21 is a hardware server, it may be, for example, a network server or a cloud server, etc. If the information processing device 21 is a software server, it may be, for example, server software or a server program, etc. If the target station 2 is mobile, the information processing device 21 may be a mobile terminal. The information processing device 21 controls the receiving unit 22, the transmitting unit 23, and the communication unit 24.

[0026] The receiving unit 22 receives signals from satellite 6A or other base stations and demodulates the received signals. The receiving unit 22 can store the demodulated signals in a memory device or the like of the information processing device 21. The receiving unit 22 comprises a control unit 220, a receiving antenna 221, a demodulation unit 222, a positioning unit 223, and a display unit 224. The control unit 220 controls some or all of the functions of the receiving unit 22. That is, the control unit 220 can control and manage the demodulation unit 222, the positioning unit 223, and the display unit 224.

[0027] The receiving antenna 221 is, for example, a GPS receiving antenna capable of receiving positioning signals 61 from satellite 6A. The receiving antenna 221 is not limited to one antenna, but may have multiple antennas. For example, the receiving antenna 221 may have antennas capable of receiving signals in a frequency band different from the GPS frequency band, in addition to a GPS receiving antenna. These different bands may be, for example, the 3.7GHz band, the 4.5GHz band, the 28GHz band, etc. If the receiving antenna 221 has antennas capable of receiving signals in a frequency band different from the GPS frequency band, the receiving unit 22 may have a demodulation unit corresponding to the frequency band of the receivable signals and the communication method.

[0028] The demodulation unit 222 demodulates the signal received by the receiving antenna 221. When the receiving antenna 221 receives a positioning signal 61 from satellite 6A, the demodulation unit 222 demodulates the positioning signal 61 received by the receiving antenna 221. For example, the demodulation unit 222 performs despread spectrum processing on the positioning signal 61 to obtain time information, orbital information, and information about satellite 6A transmitted by satellite 6A. If there are multiple satellites 6A, the demodulation unit 222 receives a positioning signal 61 from each satellite 6A and obtains time information, orbital information, and information about satellite 6A.

[0029] The positioning unit 223 performs GPS positioning processing and DGPS positioning correction processing. The positioning unit 223 acquires time information, orbital information, and information on artificial satellite 6A from the demodulation unit 222, and calculates the distance between artificial satellite 6A and target station 2 based on the time difference between the time when artificial satellite 6A transmits the positioning signal 61 and the time when target station 2 receives the positioning signal 61. Based on the distance between multiple artificial satellites 6A and target station 2 and the correction information 62 received from the reference station 3, the positioning unit 223 performs positioning of target station 2 and positioning correction using DGPS.

[0030] The display unit 224 acquires positioning information for the target station 2 from the positioning unit 223 and outputs the positioning information to the information processing device 21. The display unit 224 may also notify the user of the positioning information via the input / output IF 215. The display unit 224 may also output to the information processing device 21 the number of artificial satellites 6A used in the positioning information, the position information of the reference station 3 that transmitted the correction information 62, and the position information of the evaluation station 4.

[0031] The transmitting unit 23 modulates the signal generated by the information processing device 21 and transmits the signal using the transmitting antenna 231. The communication unit 24 can perform wired or wireless communication between the target station 2 and external devices connected to the target station 2. For example, the communication unit 24 may transmit positioning information of the target station 2 to the reference station 3 and the evaluation station 4 via the network 8 or the like.

[0032] In Figure 2, the receiving unit 22 and the transmitting unit 23 are provided separately from the information processing device 21, but the information processing device 21 may also have the functions of the receiving unit 22 and the transmitting unit 23. For example, some of the functions of the receiving unit 22 and the transmitting unit 23 may be implemented in hardware or software and stored in the information processing device 21. Similarly, some or all of the functions of the communication unit 24 may be implemented in hardware or software and stored in the information processing device 21.

[0033] (Composition of Base Station 3) Figure 3 is a block diagram showing the configuration of a reference station 3 according to one embodiment of the present disclosure. The reference station 3 comprises an information processing device 31, a receiving unit 32, a transmitting unit 33, and a communication unit 34. The information processing device 31 is a computer, and may be, for example, a personal computer, a workstation, a mobile terminal, a hardware server, a software server, etc. If the information processing device 31 is a hardware server, it may be, for example, a network server or a cloud server, etc. If the information processing device 31 is a software server, it may be, for example, server software or a server program, etc. If the reference station 3 is mobile, the information processing device 31 may be a mobile terminal. The information processing device 31 controls the receiving unit 32, the transmitting unit 33, and the communication unit 34.

[0034] The receiving unit 32 receives signals from satellite 6A or other base stations and demodulates the received signals. The receiving unit 32 can store the demodulated signals in a memory device or the like of the information processing device 31. The receiving unit 32 comprises a control unit 320, a receiving antenna 321, a demodulation unit 322, a positioning unit 323, a mask generation unit 324, a correction information generation unit 325, and a mask evaluation unit 326. The control unit 320 controls some or all of the functions of the receiving unit 32. That is, the control unit 320 can control and manage the demodulation unit 322, the positioning unit 323, the mask generation unit 324, the correction information generation unit 325, and the mask evaluation unit 326.

[0035] The receiving antenna 321 is, for example, a GPS receiving antenna capable of receiving positioning signals 61 from satellite 6A. The receiving antenna 321 is not limited to one antenna, but may have multiple antennas. For example, the receiving antenna 321 may have antennas capable of receiving signals in a frequency band different from the GPS frequency band, in addition to a GPS receiving antenna. These different bands may be, for example, the 3.7GHz band, the 4.5GHz band, the 28GHz band, etc. If the receiving antenna 321 has antennas capable of receiving signals in a frequency band different from the GPS frequency band, the receiving unit 32 may have a demodulation unit corresponding to the frequency band of the receivable signals and the communication method.

[0036] The demodulation unit 322 demodulates the signal received by the receiving antenna 321. When the receiving antenna 321 receives a positioning signal 61 from the satellite 6A, the demodulation unit 322 demodulates the positioning signal 61 received by the receiving antenna 321. For example, the demodulation unit 322 performs despread spectrum processing on the positioning signal 61 to obtain time information, orbital information, and information about the satellite 6A transmitted by the satellite 6A. If there are multiple satellites 6A, the demodulation unit 322 receives a positioning signal 61 from each satellite 6A and obtains time information, orbital information, and information about the satellite 6A.

[0037] The positioning unit 323 performs GPS positioning processing. The positioning unit 323 obtains time information, orbital information, and information about the artificial satellite 6A from the demodulation unit 322. Based on the time difference between the time when the artificial satellite 6A transmits the positioning signal 61 and the time when the base station 3 receives the positioning signal 61, the positioning unit 323 calculates the distance between the artificial satellite 6A and the base station 3.

[0038] The mask generation unit 324 calculates the difference between the TEC contained in the ionosphere 9B between the satellite 6A and the reference station 3 and the TEC contained in the ionosphere 9A between the satellite 6A and the evaluation station 4, and calculates the TEC difference amount for each elevation angle and azimuth angle between the satellite 6A and the evaluation station 4. Based on the TEC difference amount for each elevation angle and azimuth angle, the mask generation unit 324 generates an elevation angle and azimuth mask. Note that when generating the elevation angle and azimuth mask, the mask generation unit 324 may generate an elevation angle and azimuth mask that corresponds not only to the elevation angle and azimuth angle, but also to time and the position information of the evaluation station 4.

[0039] The correction information generation unit 325 acquires the positioning signal 61, the time information contained in the positioning signal 61, the orbital information, and the information of the satellite 6A from the demodulation unit 322, and generates correction information 62 based on the elevation angle and azimuth angle between the reference station 3 and the satellite 6A, and the elevation angle and azimuth angle mask. The correction information generation unit 325 decides whether or not to generate correction information 62 depending on the elevation angle and azimuth angle between the reference station 3 and the satellite 6A, and the value of the elevation angle and azimuth angle mask. If there are multiple satellites 6A, the positioning unit 323, the mask generation unit 324, the correction information generation unit 325, and the mask evaluation unit 326 decide whether or not to generate correction information 62 for each satellite 6A. The correction information generation unit 325 may also generate correction information 62 for all elevation angles and azimuth angles between the reference station 3 and the satellite 6A. In this case, the target station 2 may decide whether or not to use the correction information 62 of satellite 6A for each elevation angle and azimuth angle based on the values ​​of the elevation angle and azimuth angle mask.

[0040] The mask evaluation unit 326 evaluates the correction information 62 based on the positioning information at evaluation station 4 and the generated correction information 62. The mask evaluation unit 326 acquires the positioning signal 61 at evaluation station 4 and the positioning information corresponding to the positioning signal 61 at evaluation station 4, and performs positioning correction using DGPS based on the correction information 62 generated by the correction information generation unit 325. The mask evaluation unit 326 calculates the error between the positioning information obtained by positioning correction using DGPS and the known position information of evaluation station 4 (for example, positioning information based on the positioning signal 61 at evaluation station 4). Using the calculated error, the mask evaluation unit 326 modifies the threshold used in the mask generation unit 324. For example, if the calculated error is greater than or equal to a predetermined value, the mask evaluation unit 326 may reduce the threshold value. Alternatively, the mask evaluation unit 326 may use the Dilution Of Precision (DOP) as the evaluation quantity and modify the threshold.

[0041] The transmitting unit 33 modulates the signal generated by the information processing device 31 and transmits the signal using the transmitting antenna 331. For example, the transmitting unit 33 may transmit the elevation angle and azimuth mask and correction information 62 to the target station 2 via the artificial satellite 6B. The communication unit 34 can perform wired or wireless communication between the reference station 3 and external equipment connected to the reference station 3. For example, the communication unit 34 may transmit the elevation angle and azimuth mask and correction information 62 to the target station 2 via the network 8 or the like.

[0042] In Figure 3, the receiving unit 32 and the transmitting unit 33 are provided separately from the information processing device 31, but the information processing device 31 may also have the functions of the receiving unit 32 and the transmitting unit 33. For example, some of the functions of the receiving unit 32 and the transmitting unit 33 may be implemented in hardware or software and stored in the information processing device 31. Similarly, some or all of the functions of the communication unit 34 may be implemented in hardware or software and stored in the information processing device 31.

[0043] (Composition of Evaluation Bureau 4) Figure 4 is a block diagram showing the configuration of an evaluation station 4 according to one embodiment of the present disclosure. The evaluation station 4 comprises an information processing device 41, a receiving unit 42, a transmitting unit 43, and a communication unit 44. The information processing device 41 is a computer, and may be, for example, a personal computer, a workstation, a mobile terminal, a hardware server, a software server, etc. If the information processing device 41 is a hardware server, it may be, for example, a network server or a cloud server, etc. If the information processing device 41 is a software server, it may be, for example, server software or a server program, etc. If the evaluation station 4 is mobile, the information processing device 41 may be a mobile terminal. The information processing device 41 controls the receiving unit 42, the transmitting unit 43, and the communication unit 44.

[0044] The receiving unit 42 receives signals from satellite 6A or other base stations and demodulates the received signals. The receiving unit 42 can store the demodulated signals in a memory device or the like of the information processing device 41. The receiving unit 42 comprises a control unit 420, a receiving antenna 421, a demodulation unit 422, and a positioning unit 423. The control unit 420 controls some or all of the functions of the receiving unit 42. That is, the control unit 420 can control and manage the demodulation unit 422 and the positioning unit 423.

[0045] The receiving antenna 421 is, for example, a GPS receiving antenna capable of receiving positioning signals 61 from satellite 6A. The receiving antenna 421 is not limited to one antenna, but may have multiple antennas. For example, the receiving antenna 421 may have antennas capable of receiving signals in a frequency band different from the GPS frequency band, in addition to a GPS receiving antenna. These different bands may be, for example, the 3.7GHz band, the 4.5GHz band, the 28GHz band, etc. If the receiving antenna 421 has antennas capable of receiving signals in a frequency band different from the GPS frequency band, the receiving unit 42 may have a demodulation unit corresponding to the frequency band of the receivable signals and the communication method.

[0046] The demodulation unit 422 demodulates the signal received by the receiving antenna 421. When the receiving antenna 421 receives a positioning signal 61 from satellite 6A, the demodulation unit 422 demodulates the positioning signal 61 received by the receiving antenna 421. For example, the demodulation unit 422 performs despread spectrum processing on the positioning signal 61 to obtain time information, orbital information, and information about satellite 6A transmitted by satellite 6A. If there are multiple satellites 6A, the demodulation unit 422 receives a positioning signal 61 from each satellite 6A and obtains time information, orbital information, and information about satellite 6A.

[0047] The positioning unit 423 performs GPS positioning processing. The positioning unit 423 obtains time information, orbital information, and information about the artificial satellite 6A from the demodulation unit 422, and calculates the distance between the artificial satellite 6A and the evaluation station 4 based on the time difference between the time when the artificial satellite 6A transmits the positioning signal 61 and the time when the evaluation station 4 receives the positioning signal 61. If the evaluation station 4 is a base station fixed in a certain location, predetermined location information may be used as the location information of the evaluation station 4.

[0048] The transmitting unit 43 modulates the signal generated by the information processing device 41 and transmits the signal using the transmitting antenna 431. The communication unit 44 can perform wired or wireless communication between the evaluation station 4 and external devices connected to the evaluation station 4. For example, the communication unit 44 may transmit the location information of the evaluation station 4 to a reference station 3 or the like via a network 8 or the like.

[0049] In Figure 4, the receiving unit 42 and the transmitting unit 43 are provided separately from the information processing device 41, but the information processing device 41 may also have the functions of the receiving unit 42 and the transmitting unit 43. For example, some of the functions of the receiving unit 42 and the transmitting unit 43 may be implemented in hardware or software and stored in the information processing device 41. Similarly, some or all of the functions of the communication unit 44 may be implemented in hardware or software and stored in the information processing device 41.

[0050] Figure 5 is a block diagram showing the hardware configuration of an information processing device 21 according to one embodiment of the present disclosure. The information processing device 21 comprises a CPU 211, a ROM 212, a RAM 213, a storage device 214, an input / output interface (IF) 215, and a communication interface (IF) 216. The CPU 211, ROM 212, RAM 213, storage device 214, input / output interface (IF) 215, and communication interface (IF) 216 are interconnected via a bus 219 so as to be able to communicate with each other.

[0051] The CPU 211 is the Central Processing Unit. The CPU 211 controls each part of the information processing device 21 using application programs. The ROM 212 is read-only memory. The ROM 212 is composed of non-volatile memory and stores application programs for controlling each part of the information processing device 21. The RAM 213 is random access memory. The RAM 213 provides the memory area necessary for the operation of the CPU 211. The storage device 214 is a large-capacity storage device such as a hard disk drive.

[0052] The input / output IF215 is an input / output interface for receiving and outputting audio from the user to the information processing device 21, and for sending and receiving data or information between the information processing device 21 and other devices. The input / output IF215 may include a mouse, touch panel, trackball, keyboard, earphones, headphones, speaker, display, etc. The user can operate the information processing device 21 via the input / output IF215. The communication IF216 enables communication between the information processing device 21 and other devices via wired communication and / or wireless communication.

[0053] Note that the information processing device 31 and the information processing device 41 may have the same hardware configuration as the information processing device 21. In the following description, this embodiment will be explained assuming that the information processing device 21, the information processing device 31, and the information processing device 41 have the same hardware configuration.

[0054] Figure 6 is a schematic diagram showing the TEC difference between a reference station 3 and an evaluation station 4 according to one embodiment of the disclosure. The horizontal axis of Figure 6 represents time T, and the vertical axis represents the TEC difference between the reference station 3 and the evaluation station 4. The TEC difference is obtained, for example, by calculating the absolute value of the difference between the TEC amount between the reference station 3 and the satellite 6A and the TEC amount between the evaluation station 4 and the satellite 6A. The TEC difference is calculated in the mask generation unit 324 of the reference station 3. The elevation angle AL shown at the bottom of time T is the elevation angle between the receiving antenna 321 of the reference station 3 and the satellite 6A, and the azimuth angle AZ shown at the bottom of time T is the azimuth angle between the receiving antenna 321 of the reference station 3 and the satellite 6A. Figure 6 shows the positional relationship between the reference station 3 and the satellite 6A and the relationship between the TEC difference between the reference station 3 and the evaluation station 4 at time T. Note that the TEC difference shown in Figure 6 is calculated for each of the multiple satellites 6A.

[0055] The TEC difference is calculated for a predetermined day and a predetermined time period during the ionospheric disturbance period. The predetermined day may be any single day or any multiple days during the ionospheric disturbance period. The TEC difference may be calculated, for example, for a predetermined time period on any single day during the ionospheric disturbance period. The predetermined time period may be, for example, from 0:00 to 3:00, from 12:30 to 14:00, etc. If the predetermined day is multiple days, the predetermined time period may be different for each day, or the predetermined time period may span multiple days. In the example in Figure 6, the TEC difference is shown calculated every hour, but in the practical examples of the present disclosure, the TEC difference can be calculated at intervals of any number of seconds. In the embodiments of the present disclosure, an interval of any number of seconds is called an "epoch," and the TEC difference is calculated for each epoch. However, in Figure 6 of this embodiment, for the sake of simplicity, the epoch is assumed to have an interval of one hour.

[0056] In Figure 6, the smaller the TEC difference per epoch, the smaller the difference between the TEC contained in ionosphere 9A between satellite 6A and evaluation station 4 in Figure 1 and the TEC contained in ionosphere 9B between satellite 6A and reference station 3 in Figure 1. In other words, the smaller the TEC difference per epoch, the smaller the ionospheric delay error. On the other hand, the larger the TEC difference per epoch, the larger the ionospheric delay error. Therefore, if the TEC difference in a given epoch is large, positioning correction using DGPS may result in a deterioration of positioning accuracy.

[0057] The mask generation unit 324 compares the TEC difference amount for each epoch with a predetermined threshold ε. The threshold ε can be considered an indicator of the acceptable TEC difference amount for each epoch in positioning correction using DGPS. If the TEC difference amount is greater than the predetermined threshold ε, the mask generation unit 324 acquires the elevation angle AL and azimuth angle AZ of satellite 6A for that epoch. Assuming that the TEC difference amount is large (i.e., the accuracy of positioning correction using DGPS is poor) for the acquired elevation angle AL and azimuth angle AZ, the mask generation unit 324 sets an elevation angle and azimuth angle mask so that positioning correction using DGPS is not performed for the acquired elevation angle AL and azimuth angle AZ.

[0058] On the other hand, if the TEC difference amount is less than or equal to a predetermined threshold ε, the mask generation unit 324 acquires the elevation angle AL and azimuth angle AZ of satellite 6A in that epoch. For the acquired elevation angle AL and azimuth angle AZ, the TEC difference amount is considered to be small (i.e., the accuracy of positioning correction using DGPS is good), and the mask generation unit 324 sets the elevation angle and azimuth angle mask so that positioning correction using DGPS is performed for the acquired elevation angle AL and azimuth angle AZ. In this way, the mask generation unit 324 calculates the TEC difference amount for multiple elevation angles AL and azimuth angles AZ and sets an elevation angle and azimuth angle mask for each elevation angle AL and azimuth angle AZ.

[0059] Figure 7 is a schematic diagram showing a method for generating an elevation angle and azimuth angle mask according to one embodiment of the present disclosure. In Figure 7, the values ​​0, 90, 180, and 270 on the circumference of the sky plot of the elevation angle and azimuth angle mask represent the azimuth angle. In Figure 7, for the sake of simplicity, an example of a method for generating an elevation angle and azimuth angle mask is described, focusing on the azimuth angle divided into four sections without considering the elevation angle. In the example in Figure 7, the mask generation unit 324 generates elevation angle and azimuth angle masks for azimuth angles of 0 degrees (including azimuth angles of 0 degrees or more and less than 90 degrees), 90 degrees (including azimuth angles of 90 degrees or more and less than 180 degrees), 180 degrees (including azimuth angles of 180 degrees or more and less than 270 degrees), and 270 degrees (including azimuth angles of 270 degrees or more and less than 360 degrees). For the specified dates and times D1, D2, and D3, which are specified time periods on specified days, the mask generation unit 324 generates elevation and azimuth masks. Preferably, the specified days are different days. The specified time periods may be the same time period or different time periods.

[0060] At date and time D1, there are time periods when the TEC difference is greater than the threshold ε for azimuth angles of 0 degrees, 180 degrees, and 270 degrees, but there are no time periods when the TEC difference is greater than the threshold ε for azimuth angles of 90 degrees. In this case, positioning correction using DGPS cannot be performed for azimuth angles of 0 degrees, 180 degrees, and 270 degrees, so the mask generation unit 324 sets a weight of 1 for azimuth angles of 0 degrees, 180 degrees, and 270 degrees. Positioning correction using DGPS can be performed for azimuth angles of 90 degrees, so the mask generation unit 324 sets a weight of 0 for azimuth angles of 90 degrees.

[0061] At time D2, there are time periods when the TEC difference is greater than the threshold ε for 180-degree and 270-degree azimuth angles, but there are no time periods when the TEC difference is greater than the threshold ε for 0-degree and 90-degree azimuth angles. In this case, positioning correction using DGPS cannot be performed for 180-degree and 270-degree azimuth angles, so the mask generation unit 324 sets a weight of 1 for 180-degree and 270-degree azimuth angles. Positioning correction using DGPS can be performed for 0-degree and 90-degree azimuth angles, so the mask generation unit 324 sets a weight of 0 for 0-degree and 90-degree azimuth angles.

[0062] At date and time D3, there is a period in which the TEC difference amount is greater than the threshold ε for an azimuth angle of 180 degrees, but there is no period in which the TEC difference amount is greater than the threshold ε for an azimuth angle of 0 degrees, an azimuth angle of 90 degrees, and an azimuth angle of 270 degrees. In this case, positioning correction using DGPS cannot be performed for an azimuth angle of 180 degrees, so the mask generation unit 324 sets a weight of 1 for an azimuth angle of 180 degrees. Positioning correction using DGPS can be performed for an azimuth angle of 0 degrees, an azimuth angle of 90 degrees, and an azimuth angle of 270 degrees, so the mask generation unit 324 sets a weight of 0 for an azimuth angle of 0 degrees, an azimuth angle of 90 degrees, and an azimuth angle of 270 degrees.

[0063] The mask generation unit 324 synthesizes the weights for the azimuth angles obtained for the dates and times D1, D2, and D3. The weights of the azimuth angles synthesized by the mask generation unit 324 can be values ​​from 0 to 3. The synthesized weights of the azimuth angles can also be said to be values ​​that indicate the reliability of positioning correction using DGPS. If the weights of the synthesized azimuth angles are large, the positioning accuracy of positioning correction using DGPS is poor, and if the weights of the synthesized azimuth angles are small, the positioning accuracy of positioning correction using DGPS is good. Therefore, depending on the value of the weights of the synthesized azimuth angles, the correction information generation unit 325 can determine whether or not to generate correction information 62 and whether or not to perform positioning correction using DGPS. For example, the correction information generation unit 325 may decide not to generate correction information 62 and not to perform positioning correction using DGPS for azimuth angles with a weight value of 2 or more.

[0064] In the example in Figure 7, the number of days in the predetermined day was set to 3, but the predetermined day may be set to a larger number of days depending on the duration of the ionospheric disturbance period, etc. For example, if the number of days in the predetermined day is 10, the weight of the azimuth angle synthesized by the mask generation unit 324 may be a value between 0 and 10. The value of the synthesized weight of the azimuth angle may be normalized using the number of days in the predetermined day. The normalized weight value may be a value between 0 and 1. Alternatively, the number of days in the predetermined day may be 1. In other words, it is not always necessary to synthesize the weight for the azimuth angle. If the weight for the azimuth angle is not synthesized, correction information 62 may not be generated for azimuth angles with a weight value of 1, and it may be determined that positioning correction using DGPS will not be performed. Alternatively, the weight for the azimuth angle may be synthesized using date and time D1, date and time D2, and date and time D3 as different time zones on the same day (for example, date and time D1, date and time D2, and date and time D3 are the same date and time D1, but are different time zones). For example, the time period for date and time D1 may be from 0:00 to 1:00, the time period for date and time D2 may be from 1:00 to 2:00, and the time period for date and time D3 may be from 2:00 to 3:00. In this case, the generated elevation and azimuth mask will have a composite weight of the time periods from 0:00 to 3:00 for date and time D1.

[0065] For example, when generating elevation and azimuth masks between a reference station 3 and multiple satellites 6A (wherein N is an arbitrary integer), the mask generation unit 324 performs the elevation and azimuth mask generation method shown in Figures 6 and 7 for satellites 6A-1, 6A-2, ..., 6A-N. That is, the mask generation unit 324 generates elevation and azimuth masks for satellite 6A-1, satellite 6A-2, ..., 6A-N.

[0066] For each of the multiple satellites 6A, the mask generation unit 324 can generate an elevation and azimuth mask. This allows the correction information generation unit 325 to exclude satellites 6A that transmit positioning signals 61 that may degrade positioning accuracy during periods of ionospheric disturbance. For example, an embodiment of this model will be described in the case where DGPS positioning correction can be performed using positioning signals 61 from six satellites 6A-1, 6A-2, 6A-3, 6A-4, 6A-5, and 6A-6 at a certain elevation and azimuth angle. If the positioning signals 61 from satellites 6A-1 and 6A-2 among satellites 6A-1 to 6A-6 may degrade positioning accuracy, the elevation and azimuth masks for satellite 6A-1 and satellite 6A-2 for elevation and azimuth angles may have large weight values. Therefore, the correction information generation unit 325 can generate correction information 62 without using artificial satellites 6A-1 and 6A-2.

[0067] Furthermore, by excluding satellite 6A using an elevation angle and azimuth angle mask, the number of satellite 6A used in positioning and positioning correction processing is reduced, which may worsen the accuracy of positioning and positioning correction processing. In such cases, for example, for elevation angles greater than a predetermined elevation angle, even if the TEC difference amount is greater than the threshold ε, the TEC difference amount may be considered to be less than or equal to the threshold ε.

[0068] Figure 8 is a sky plot showing an elevation-azimuth mask according to one embodiment of the present disclosure. Figure 8 shows the elevation-azimuth mask shown in Figure 7 in more specific and detailed terms. In Figure 8, the numerical values ​​on the circumference of the elevation-azimuth mask represent the azimuth angle, and the numerical values ​​on the concentric circles of the elevation-azimuth mask represent the elevation angle. The elevation-azimuth mask has a predetermined elevation resolution and a predetermined azimuth resolution.

[0069] The predetermined elevation angle resolution is a parameter that divides the elevation angle from 0 to 90 degrees into multiple angular ranges. The predetermined elevation angle resolution may be, for example, 1 degree, 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, etc. If the predetermined elevation angle resolution is 30 degrees, the elevation angle from 0 to 90 degrees is divided into three ranges: an elevation angle of 0 degrees or more and less than 30 degrees, an elevation angle of 30 degrees or more and less than 60 degrees, and an elevation angle of 60 degrees or more and 90 degrees or less. The predetermined elevation angle resolution does not have to be constant for elevation angles from 0 to 90 degrees. For example, the predetermined elevation angle resolution may be 15 degrees for elevation angles of 0 degrees or more and less than 45 degrees, and 5 degrees for elevation angles of 45 degrees or more and 90 degrees or less.

[0070] The predetermined azimuth resolution is a parameter that divides the azimuth angle from 0 to 360 degrees into multiple angular ranges. The predetermined azimuth resolution can be, for example, 1 degree, 5 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, etc. If the predetermined azimuth resolution is 30 degrees, the azimuth angles from 0 to 360 degrees are divided into the following ranges: azimuth angles of 0 degrees or more and less than 30 degrees; azimuth angles of 30 degrees or more and less than 60 degrees; azimuth angles of 60 degrees or more and less than 90 degrees; azimuth angles of 90 degrees or more and less than 120 degrees; azimuth angles of 120 degrees or more and less than 150 degrees; azimuth angles of 150 degrees or more and less than 180 degrees; azimuth angles of 180 degrees or more and less than 210 degrees; azimuth angles of 210 degrees or more and less than 240 degrees; azimuth angles of 240 degrees or more and less than 270 degrees; azimuth angles of 270 degrees or more and less than 300 degrees; azimuth angles of 300 degrees or more and less than 330 degrees; and azimuth angles of 330 degrees or more and less than 360 degrees. The predetermined azimuth resolution does not have to be constant for azimuth angles from 0 to 360 degrees. For example, the predetermined azimuth resolution may be 15 degrees for azimuth angles of 0 degrees or more and less than 90 degrees, 5 degrees for azimuth angles of 90 degrees or more and less than 270 degrees, and 10 degrees for azimuth angles of 270 degrees or more and less than 360 degrees.

[0071] The predetermined elevation resolution and predetermined azimuth resolution may be determined based on the known size of the obstruction, the position of the obstruction, the relative positional relationship between the obstruction and the target station 2, the relative positional relationship between the obstruction and the reference station 3, the relative positional relationship between the obstruction and the evaluation station 4, and the relative positional relationship between the target station 2, the reference station 3, the evaluation station 4, and the obstruction.

[0072] In the elevation angle and azimuth angle mask of Figure 8, the predetermined elevation angle resolution is 15 degrees, and the predetermined azimuth angle resolution is 30 degrees. Weights can be set for the range of elevation angles divided by the predetermined elevation angle resolution and the range of azimuth angles divided by the predetermined azimuth angle resolution, using the method described in Figure 7. For example, for the elevation angle and azimuth angle mask of Figure 8, the correction information generation unit 325 will not generate correction information 62 for a certain satellite 6A and will not perform positioning correction using DGPS with that satellite 6A for the range of elevation angles and azimuth angles where the weight value is 2 or more. In this case, if the range of azimuth angles is 0 degrees or more and less than 360 degrees, and the range of elevation angles is 0 degrees or more and less than 30 degrees, the correction information generation unit 325 will not generate correction information 62 for that satellite 6A and will not perform positioning correction using DGPS with that satellite 6A. For example, if target station 2 can perform positioning correction using DGPS with satellites 6A, 6B, 6C, and 6D, then target station 2 can perform positioning correction using DGPS with satellites 6B, 6C, and 6D other than satellite 6A.

[0073] Figure 9 is a flowchart illustrating an example of the positioning process of evaluation station 4 according to one embodiment of the present disclosure. In the receiving unit 42 of evaluation station 4, the receiving antenna 421 receives the positioning signal 61 (corresponding to the third positioning signal) transmitted from the satellite 6A (step S101). In the receiving unit 42, the demodulation unit 422 demodulates the positioning signal 61 received by the receiving antenna 421. The positioning unit 423 uses the demodulated positioning signal 61 to perform GPS positioning processing of evaluation station 4 (step S103). The positioning unit 423 acquires time information, orbital information, and information of the satellite 6A contained in the demodulated positioning signal 61, and calculates the distance between the satellite 6A and evaluation station 4 based on the time difference between the time the satellite 6A transmitted the positioning signal 61 and the time the evaluation station 4 received the positioning signal 61. The control unit 420 stores the positioning information calculated in step S103 in the storage device of the information processing device 41 (step S105). The control unit 420 may also transmit the positioning information to the reference station 3 via the transmission unit 43 or the communication unit 44. For the positioning process from step S101 to step S105, the evaluation station 4 may store the number of artificial satellites 6A, the identification information of artificial satellites 6A, and the date and time the positioning process was performed as related positioning process information in the storage device of the information processing device 41. The evaluation station 4 performs the positioning process from step S101 to step S105 for each of the multiple artificial satellites 6A-1 to 6A-N.

[0074] Figure 10 is a flowchart showing an example of the process for generating an elevation angle and azimuth angle mask according to one embodiment of the present invention. The process for generating the elevation angle and azimuth angle mask in Figure 10 will be explained with reference to the schematic diagram showing the TEC difference amount in Figure 6 and the schematic diagram showing the method for generating the elevation angle and azimuth angle mask in Figure 7. Similar to the explanation in Figure 7, the process for generating the elevation angle and azimuth angle mask in Figure 10 will be explained assuming that the predetermined time periods on a predetermined day are date and time D1, date and time D2, and date and time D3, and similar to the explanation in Figure 6, that the epochs have an interval of 1 hour.

[0075] First, the mask generation unit 324 repeats the process from step S201 to step S205 for each epoch in Figure 6 at the date and time D1 in Figure 7. For example, if the predetermined time period is from 0:00 to 24:00 at the date and time D1, the process from step S201 to step S205 is repeated 24 times. At each epoch, the mask generation unit 324 calculates the absolute value of the difference between the TEC amount between the reference station 3 and the satellite 6A and the TEC amount between the evaluation station 4 and the satellite 6A, and calculates the TEC difference amount (step S201). The calculated TEC difference amount is compared with the threshold ε, and epochs in which the TEC difference amount is greater than the threshold ε are extracted (step S203). For example, in the epoch from 8:00 to 9:00 in Figure 6, the calculated TEC difference amount is greater than the threshold ε. Therefore, in step S203, the epoch from 8:00 to 9:00 is extracted. On the other hand, in the epoch from 9:00 to 10:00 in Figure 6, the calculated TEC difference is less than or equal to the threshold ε. Therefore, in step S203, the epoch from 9:00 to 10:00 is not extracted. In the example in Figure 6, the epochs between 0:00 and 9:00 and between 16:00 and 24:00 are extracted. The mask generation unit 324 obtains the elevation angle and azimuth angle between the reference station 3 and the satellite 6A in the epoch extracted in step S203 (step S205). For example, in the epoch from 9:00 to 10:00 in Figure 6, the elevation angle AL between the reference station 3 and the satellite 6A is 45 degrees, and the azimuth angle AZ between the reference station 3 and the satellite 6A is 90 degrees. Therefore, the mask generation unit 324 obtains the elevation angle AL of 45 degrees and the azimuth angle AZ of 90 degrees. The mask generation unit 324 sets weight values ​​for the elevation angle and azimuth angle mask corresponding to the obtained elevation angle AL and azimuth angle AZ.

[0076] For each epoch of date and time D2 and each epoch of date and time D3, the process from steps S201 to S205 described above is repeated, and the mask generation unit 324 sets weights for the elevation angle and azimuth angle masks corresponding to the elevation angle AL and azimuth angle AZ in date and time D1, date and time D2, and date and time D3. The mask generation unit 324 combines the elevation angle and azimuth angle mask of date and time D1, the elevation angle and azimuth angle mask of date and time D2, and the elevation angle and azimuth angle mask of date and time D3, and generates an elevation angle and azimuth angle mask (step S207). For example, the mask generation unit 324 can generate an elevation angle and azimuth angle mask as shown in Figure 8.

[0077] When using multiple satellites 6A-1 through 6A-N, the mask generation unit 324 performs the elevation and azimuth mask generation process shown in Figure 10 for each of the multiple satellites 6A-1 through 6A-N.

[0078] Figure 11 is a flowchart illustrating an example of the correction information generation process according to one embodiment of the present disclosure. In the receiving unit 32 of the base station 3, the receiving antenna 321 receives the positioning signal 61 (corresponding to the first positioning signal) transmitted from the artificial satellite 6A (step S301). In the receiving unit 32, the demodulation unit 322 demodulates the positioning signal 61 received by the receiving antenna 321. The positioning unit 323 uses the demodulated positioning signal 61 to perform GPS positioning processing for the base station 3. In the process of GPS positioning processing, the positioning unit 323 acquires the elevation angle and azimuth angle between the base station 3 and the artificial satellite 6A (step S303).

[0079] The correction information generation unit 325 refers to the weight values ​​of the elevation angle-azimuth mask corresponding to the acquired elevation angle and azimuth angle (step S305). The correction information generation unit 325 determines whether or not to generate correction information 62 for the acquired elevation angle and azimuth angle according to the weight values ​​of the elevation angle-azimuth mask corresponding to the acquired elevation angle and azimuth angle (step S307). For example, steps S307 and S309 below describe the case where the correction information generation unit 325 determines not to generate correction information 62 and not to perform positioning correction using DGPS for elevation angle ranges and azimuth angle ranges where the weight values ​​are 2 or more.

[0080] For example, if the elevation angle between the reference station 3 and satellite 6A is 50 degrees and the azimuth angle between the reference station 3 and satellite 6A is 290 degrees, referring to the elevation angle / azimuth mask in Figure 8, the weight value is 1. Since the weight value is less than 2 (YES in step S307), the correction information generation unit 325 generates correction information 62 and determines to perform positioning correction using DGPS (step S309). On the other hand, for example, if the elevation angle between the reference station 3 and satellite 6A is 12 degrees and the azimuth angle between the reference station 3 and satellite 6A is 45 degrees, referring to the elevation angle / azimuth mask in Figure 8, the weight value is 3. Since the weight value is 2 or more (NO in step S307), the correction information generation unit 325 does not generate correction information 62, determines not to perform positioning correction using DGPS for satellite 6A, and terminates the correction information generation process.

[0081] When using multiple satellites 6A-1 through 6A-N, the correction information generation unit 325 performs the correction information generation process shown in Figure 11 for each of the multiple satellites 6A-1 through 6A-N.

[0082] Figure 12 is a flowchart showing an example of an evaluation process for an elevation angle and azimuth angle mask according to one embodiment of the present disclosure. The mask evaluation unit 326 acquires a positioning signal 61 received at evaluation station 4, which is located near the target station 2 (step S401). The mask evaluation unit 326 may acquire not only the positioning signal 61 received at evaluation station 4, but also positioning information of evaluation station 4 based on positioning by evaluation station 4. Using the elevation angle and azimuth angle mask generated by the mask generation unit 324, the correction information 62 generated by the correction information generation unit 325, and the positioning signal 61 acquired from evaluation station 4, DGPS positioning correction is performed for evaluation station 4 (step S403).

[0083] The mask evaluation unit 326 calculates an error using the positioning information of evaluation station 4 and the positioning information obtained by DGPS positioning correction in step S403 (step S405). The mask evaluation unit 326 calculates the error between the positioning information of evaluation station 4 obtained by positioning correction using DGPS and the positioning information based on the positioning signal 61 at evaluation station 4. Instead of the positioning information based on the positioning signal 61 at evaluation station 4, the error may be calculated using known location information of evaluation station 4. The mask evaluation unit 326 determines whether the error calculated in step S405 is greater than or equal to a predetermined value (step S407).

[0084] If the error is greater than or equal to a predetermined value (YES in step S407), the mask evaluation unit 326 modifies the threshold ε used in the mask generation unit 324 using the calculated error (step S409). For example, if the calculated error is greater than or equal to a predetermined value, the mask evaluation unit 326 may reduce the value of the threshold ε. In the evaluation process of the elevation angle and azimuth angle mask, the threshold ε may be modified using evaluation quantities other than the error between the positioning information of the evaluation station 4 obtained by positioning correction using DGPS and the positioning information based on the positioning signal 61 at the evaluation station 4. For example, if there is no interval on a predetermined day in which the TEC difference amount is less than or equal to the threshold ε, the mask evaluation unit 326 may increase the value of the threshold ε. For example, if the values ​​of all weights in the elevation angle and azimuth angle mask are greater than or equal to a predetermined value, the mask evaluation unit 326 may increase the value of the threshold ε. On the other hand, if the error is not greater than or equal to a predetermined value (NO in step S407), the mask evaluation unit 326 does not modify the threshold ε and terminates the evaluation process of the elevation angle and azimuth angle mask.

[0085] Figure 13 is a flowchart illustrating an example of the positioning process of a target station according to one embodiment of the present disclosure. The positioning process of the target station 2 will be described in the case where the target station 2 receives positioning signals 61 from satellites 6A-1 to 6A-N. In the receiving unit 22 of the target station 2, the receiving antenna 221 receives a positioning signal 61 (corresponding to the second positioning signal) transmitted from one of the multiple satellites 6A, satellite 6A-n (n=1, 2, ..., N) (step S501). In the receiving unit 22, the demodulation unit 222 demodulates the positioning signal 61 received by the receiving antenna 221. Furthermore, the target station 2 acquires an elevation angle and azimuth angle mask and correction information 62 from the reference station 3 (step S503). For example, when the reference station 3 transmits the elevation angle and azimuth mask and correction information 62 to the target station 2 via satellite 6B, the receiving unit 22 of the target station 2 receives the elevation angle and azimuth mask and correction information 62 transmitted from satellite 6B via the receiving antenna 221. For example, when the reference station 3 transmits the elevation angle and azimuth mask and correction information 62 to the target station 2 via network 8, the communication unit 34 of the target station 2 receives the elevation angle and azimuth mask and correction information 62.

[0086] The positioning unit 223 uses the elevation angle and azimuth angle between the target station 2 and the satellite 6A-n, acquired during the demodulation process in step S501, to refer to the elevation-azimuth mask acquired in step S503 (step S505). The positioning unit 223 determines whether the weight values ​​of the elevation-azimuth mask for the acquired elevation angle and azimuth angle are greater than or equal to a predetermined value (step S507). If the weight values ​​of the elevation-azimuth mask are greater than or equal to a predetermined value (YES in step S507), the positioning unit 223 determines that the positioning signal 61 from the satellite 6A-n will not be used for GPS positioning (step S509). On the other hand, if the weight values ​​of the elevation-azimuth mask are not greater than or equal to a predetermined value (NO in step S507), the positioning unit 223 determines that the positioning signal 61 from the satellite 6A-n will be used for GPS positioning (step S511).

[0087] For multiple satellites 6A-1 through 6A-N, the positioning unit 223 performs the processes from steps S501 to S511. In step S511, based on the positioning signals 61 from multiple satellites 6A that the positioning unit 223 has determined to use, and the elevation angle / azimuth mask and correction information 62 acquired in step S503, the positioning unit 223 performs GPS positioning processing and DGPS positioning correction for the target station 2 (step S513). It is desirable for the target station 2 to perform GPS positioning and DGPS positioning correction using positioning signals 61 from at least four different satellites 6A. Therefore, in step S513, if the number of satellites 6A used for GPS positioning is less than four, for example, a satellite 6A that will use the positioning signal 61 may be selected from among the satellites 6A that were determined not to use the positioning signal 61 in step S509.

[0088] The positioning unit 223 transmits positioning information to the display unit 224, and the display unit 224 displays the positioning information on the input / output IF 215 of the information processing device 21 (step S515). The display unit 224 may also display the number of artificial satellites 6A used by the target station 2 when performing GPS positioning processing and DGPS positioning correction, the position information of the reference station 3 that transmitted the elevation angle / azimuth angle mask and correction information 62, and the position information of the evaluation station 4. Referring to the display by the display unit 224, the user may transmit feedback information to the reference station 3 to improve the accuracy of GPS positioning and DGPS positioning correction. The reference station 3 receives the feedback information from the user and may reduce the predetermined value used by the mask evaluation unit 326 when evaluating the error in S407 of Figure 12.

[0089] In this embodiment, the reference station 3 generates elevation and azimuth masks and correction information 62 for multiple artificial satellites 6A. The reference station 3 can exclude artificial satellites 6A that have conditions that would worsen the accuracy of positioning processing and positioning correction processing from among the multiple artificial satellites 6A by using the elevation and azimuth mask. This makes it possible to perform accurate positioning processing and positioning correction processing for the target station 2, even when there is a large ionospheric delay difference between the reference station 3 and the target station 2.

[0090] [Second Embodiment] In the first embodiment, evaluation station 4 is located near target station 2. In this embodiment, target station 2 is a mobile station and moves from the vicinity of evaluation station 4A to the vicinity of evaluation station 4B. Components that are the same in the configuration of the positioning system 1 in this embodiment and the configuration of the positioning system 1 in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0091] When target station 2 is located near evaluation station 4A, base station 3 transmits an elevation / azimuth mask and correction information 62 generated using the positioning signal 61 received at evaluation station 4A to target station 2, and target station 2 performs GPS positioning and DGPS positioning correction. When target station 2 moves near evaluation station 4B, base station 3 transmits an elevation / azimuth mask and correction information 62 generated using the positioning signal 61 received at evaluation station 4B to target station 2, and target station 2 performs GPS positioning and DGPS positioning correction.

[0092] Target station 2 may transmit location information obtained by GPS positioning to base station 3. Based on the location information received from target station 2, base station 3 may select an appropriate evaluation station 4 from among a plurality of evaluation stations 4 located near target station 2. For example, base station 3 may select one or more evaluation stations 4 located within a predetermined distance from target station 2 and notify target station 2 of the location information and identification information of one or more evaluation stations 4. Furthermore, base station 3 may transmit the elevation angle and azimuth angle mask and correction information 62 generated for one or more evaluation stations 4 to target station 2.

[0093] Target station 2 can perform GPS positioning and DGPS positioning correction using one or more evaluation stations 4 notified by base station 3, an elevation angle / azimuth mask, and correction information 62. Furthermore, target station 2 can select an appropriate evaluation station 4, an elevation angle / azimuth mask, and correction information 62 based on the position information obtained by GPS positioning and DGPS positioning correction. For example, target station 2 may select the nearest evaluation station 4. Target station 2 may also select an evaluation station 4 that is free from obstructions, etc., in its vicinity based on map information.

[0094] The predetermined distance from the target station 2 may be determined, for example, based on the threshold ε in Figure 6 and the length of the interval where the TEC difference is less than or equal to the threshold. Alternatively, it may be predetermined based on the surrounding topography, such as urban areas, city centers, or mountainous areas, by referring to map information.

[0095] Alternatively, instead of target station 2, the reference station 3 may select evaluation station 4 and notify target station 2 of the selected evaluation station 4. For example, reference station 3 selects an evaluation station 4 from among several evaluation stations 4 located near target station 2 and notifies target station 2 of the identification information of evaluation station 4. Reference station 3 may further transmit the elevation angle and azimuth angle mask and correction information 62 generated for the evaluation station 4 to target station 2.

[0096] Target station 2 can transmit location information to base station 3 while moving and receive location information, identification information, elevation angle and azimuth angle mask, and correction information 62 from base station 3 for one or more evaluation stations 4. If the distance between target station 2 and base station 3 exceeds a predetermined distance, base station 3 may hand over communication with target station 2 to another base station 3.

[0097] In this embodiment, while the target station 2 is moving, it receives location information, identification information, elevation and azimuth masks, and correction information 62 from the reference station 3 for one or more evaluation stations 4. The target station 2 can perform GPS positioning and DGPS positioning correction and select an appropriate evaluation station 4, elevation and azimuth mask, and correction information 62. In this way, even when the target station 2 is a mobile station, it becomes possible to perform accurate positioning and positioning correction processing for the target station 2.

[0098] Reference station 3 may apply the configuration disclosed in this application for a predetermined period. For example, reference station 3 may apply the configuration disclosed in this application during ionospheric disturbance periods and not apply the configuration disclosed in this application during ionospheric quiescence periods or periods other than ionospheric disturbance periods. Alternatively, elevation angle and azimuth mask and correction information 62 for ionospheric disturbance periods and elevation angle and azimuth mask and correction information 62 for ionospheric quiescence periods may be generated, and reference station 3 may switch between applying them to ionospheric disturbance periods and ionospheric quiescence periods.

[0099] Depending on the positional relationship between target station 2, reference station 3, and evaluation station 4, reference station 3 and evaluation station 4 may be selected to generate the elevation angle azimuth mask and correction information 62. For example, if a reference station 3 cannot generate an elevation angle azimuth mask and correction information 62 that ensures sufficient accuracy for target station 2, target station 2 may select another reference station 3. The other reference station 3 may generate the elevation angle azimuth mask and correction information 62 and transmit it to target station 2. Alternatively, a reference station 3 may select another reference station 3 and forward information about target station 2 and a processing command to generate the elevation angle azimuth mask and correction information 62.

[0100] [Other embodiments] Figure 14 is a block diagram showing a positioning system according to one embodiment of the present disclosure. The positioning system 1000 comprises a reference station 1001 and a target station 1002. The reference station 1001 receives a first positioning signal from an artificial satellite. The target station 1002 receives a second positioning signal from an artificial satellite. The reference station 1001 uses the total number of ionospheric electrons based on a third positioning signal received from an artificial satellite by an evaluation station located near the target station 1002, and the total number of ionospheric electrons based on the first positioning signal, to generate an elevation-azimuth mask that includes information on the elevation angle and azimuth angle of the artificial satellite and determines whether or not to generate correction information. The reference station 1001 generates correction information using the positioning error based on the first positioning signal. The target station 1002 calculates position information based on the second positioning signal, the elevation-azimuth angle information, and the correction information corresponding to the elevation-azimuth angle.

[0101] Furthermore, the processing method of recording a program that operates the configuration of each embodiment to realize the functions of each embodiment on a recording medium, reading the program recorded on the recording medium as code, and executing it on a computer is also included in the scope of each embodiment. In other words, computer-readable recording media are also included in the scope of each embodiment. Moreover, not only the recording medium on which the above-mentioned computer program is recorded, but also the computer program itself is included in each embodiment.

[0102] Examples of recording media that can be used include floppy disks, hard disks, optical disks, magneto-optical disks, CD-ROMs (Compact Disc-Read Only Memory), magnetic tapes, non-volatile memory cards, and ROMs. Furthermore, the scope of each embodiment is not limited to programs that perform processing on the recording media alone, but also includes programs that operate on an OS (Operating System) in cooperation with other software and the functions of expansion boards to perform processing.

[0103] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and detailed description of the present disclosure can be made that will be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0104] Some or all of the above embodiments may also be described as follows, but are not limited to the following:

[0105] (Note 1) A reference station that receives the first positioning signal from an artificial satellite, A target station that receives a second positioning signal from the aforementioned artificial satellite, The reference station generates an elevation and azimuth mask that includes information on the elevation and azimuth of the satellite and determines whether or not to generate correction information, using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the target station and the total number of ionospheric electrons based on the first positioning signal. The reference station generates the correction information using the positioning error based on the first positioning signal. The aforementioned target station is a positioning system that calculates location information based on the second positioning signal, the information, and the correction information corresponding to the elevation angle and azimuth angle.

[0106] (Note 2) The positioning system according to Appendix 1, wherein the information included in the elevation angle and azimuth angle mask comprises elevation angle information and azimuth angle information between the reference station and the artificial satellite, and weights corresponding to the elevation angle information and the azimuth angle information.

[0107] (Note 3) The positioning system as described in Appendix 2, wherein if the weights corresponding to the elevation angle and azimuth angle based on the second positioning signal are greater than or equal to a predetermined value, the target station calculates the position information based on the second positioning signal without using the correction information.

[0108] (Note 4) The reference station calculates the difference in the total number of electrons between the total number of electrons in the ionosphere based on the third positioning signal and the total number of electrons in the ionosphere based on the first positioning signal, with respect to the elevation angle information and the azimuth angle information. The positioning system as described in Appendix 2, wherein the weight is set to 1 when the total difference in the number of electrons is greater than or equal to a predetermined threshold.

[0109] (Note 5) The aforementioned reference station calculates the total electron count difference amount for the elevation angle information and the azimuth angle information at multiple different time periods. The reference station sets a plurality of weights for each of the total electron count difference amounts in the plurality of different time periods, The positioning system described in Appendix 4, wherein the reference station sets the sum of the plurality of weights to the weights corresponding to the elevation angle information and the azimuth angle information.

[0110] (Note 6) The positioning system described in Appendix 4, wherein the reference station calculates the error between the position information of the evaluation station calculated based on the correction information and the position information of the evaluation station based on the third positioning signal, and updates the predetermined threshold based on the error.

[0111] (Note 7) The reference station notifies the reference station of the identification information of the evaluation station located within a predetermined distance from the target station. The positioning system described in Appendix 1, wherein the target station obtains the elevation angle and azimuth angle mask and the correction information for the evaluation station corresponding to the identification information from the reference station.

[0112] (Note 8) Acquisition means for acquiring correction information and an elevation angle and azimuth mask including information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite, Receiving means for receiving a second positioning signal from the artificial satellite and acquiring the elevation angle and azimuth angle between the artificial satellite and the positioning device, The system comprises a positioning means that calculates position information based on the second positioning signal, the elevation angle and the azimuth angle, the information of the elevation angle and azimuth angle mask corresponding to the elevation angle and the azimuth angle, and the correction information corresponding to the elevation angle and the azimuth angle, The elevation angle and azimuth angle mask is generated by the reference station using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the positioning device, and the total number of ionospheric electrons based on the first positioning signal. The correction information is generated by the reference station using the positioning error based on the first positioning signal in a positioning device.

[0113] (Note 9) The positioning device according to Appendix 8, wherein the information included in the elevation angle and azimuth angle mask comprises elevation angle information and azimuth angle information between the reference station and the artificial satellite, and weights corresponding to the elevation angle information and the azimuth angle information.

[0114] (Note 10) The positioning device according to Appendix 9, wherein if the weights corresponding to the elevation angle and azimuth angle based on the second positioning signal are greater than or equal to a predetermined value, the positioning device calculates the position information based on the second positioning signal without using the correction information.

[0115] (Note 11) The reference station calculates the difference in the total number of electrons between the total number of electrons in the ionosphere based on the third positioning signal and the total number of electrons in the ionosphere based on the first positioning signal, with respect to the elevation angle information and the azimuth angle information. The positioning device described in Appendix 9, wherein the weight is set to 1 when the total difference in the number of electrons is greater than or equal to a predetermined threshold.

[0116] (Note 12) The aforementioned reference station calculates the total electron count difference amount for the elevation angle information and the azimuth angle information at multiple different time periods. The reference station sets a plurality of weights for each of the total electron count difference amounts in the plurality of different time periods, The positioning device described in Appendix 11, wherein the reference station sets the sum of the plurality of weights to the weights corresponding to the elevation angle information and the azimuth angle information.

[0117] (Note 13) The positioning device described in Appendix 11, wherein the reference station calculates the error between the position information of the evaluation station calculated based on the correction information and the position information of the evaluation station based on the third positioning signal, and updates the predetermined threshold based on the error.

[0118] (Note 14) The reference station notifies the reference station of the identification information of the evaluation station located within a predetermined distance range from the positioning device. The positioning device described in Appendix 8 acquires the elevation angle and azimuth angle mask and the correction information for the evaluation station corresponding to the identification information from the reference station.

[0119] (Note 15) An acquisition step of obtaining correction information and an elevation angle and azimuth mask including information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite, A receiving step of receiving a second positioning signal from the artificial satellite and obtaining the elevation angle and azimuth angle between the artificial satellite and the positioning device, The system includes a positioning step which calculates position information based on the second positioning signal, the elevation angle and the azimuth angle, the information of the elevation angle and azimuth angle mask corresponding to the elevation angle and the azimuth angle, and the correction information corresponding to the elevation angle and the azimuth angle, The elevation angle and azimuth angle mask is generated by the reference station using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the positioning device, and the total number of ionospheric electrons based on the first positioning signal. A positioning method in which the correction information is generated by the reference station using the positioning error based on the first positioning signal.

[0120] (Note 16) The positioning method according to Appendix 15, wherein the information included in the elevation angle and azimuth angle mask comprises elevation angle information and azimuth angle information between the reference station and the artificial satellite, and weights corresponding to the elevation angle information and the azimuth angle information.

[0121] (Note 17) The positioning method according to Appendix 16, wherein if the weights corresponding to the elevation angle and azimuth angle based on the second positioning signal are greater than or equal to a predetermined value, the positioning device calculates the position information based on the second positioning signal without using the correction information.

[0122] (Note 18) The reference station calculates the difference in the total number of electrons between the total number of electrons in the ionosphere based on the third positioning signal and the total number of electrons in the ionosphere based on the first positioning signal, with respect to the elevation angle information and the azimuth angle information. The positioning method described in Appendix 16, wherein the weight is set to 1 when the total difference in the number of electrons is greater than or equal to a predetermined threshold.

[0123] (Note 19) The aforementioned reference station calculates the total electron count difference amount for the elevation angle information and the azimuth angle information at multiple different time periods. The reference station sets a plurality of weights for each of the total electron count difference amounts in the plurality of different time periods, The positioning method described in Appendix 18, wherein the reference station sets the sum of the plurality of weights to the weights corresponding to the elevation angle information and the azimuth angle information.

[0124] (Note 20) The positioning method according to Appendix 18, wherein the reference station calculates an error between the position information of the evaluation station calculated based on the correction information and the position information of the evaluation station based on the third positioning signal, and updates the predetermined threshold based on the error.

[0125] (Note 21) The reference station notifies the reference station of the identification information of the evaluation station located within a predetermined distance range from the positioning device. The positioning method described in Appendix 15, wherein the positioning device obtains the elevation angle and azimuth angle mask and the correction information for the evaluation station corresponding to the identification information from the reference station.

[0126] (Note 22) An acquisition step of obtaining correction information and an elevation angle and azimuth mask including information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite, A receiving step of receiving a second positioning signal from the artificial satellite and obtaining the elevation angle and azimuth angle between the artificial satellite and the positioning device, The system includes a positioning step which calculates position information based on the second positioning signal, the elevation angle and the azimuth angle, the information of the elevation angle and azimuth angle mask corresponding to the elevation angle and the azimuth angle, and the correction information corresponding to the elevation angle and the azimuth angle, The elevation angle and azimuth angle mask is generated by the reference station using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the positioning device, and the total number of ionospheric electrons based on the first positioning signal. The correction information is a positioning program generated by the reference station using the positioning error based on the first positioning signal.

[0127] (Note 23) The positioning program described in Appendix 22 includes, wherein the information included in the elevation angle and azimuth angle mask comprises elevation angle information and azimuth angle information between the reference station and the artificial satellite, and weights corresponding to the elevation angle information and the azimuth angle information.

[0128] (Note 24) The positioning program described in Appendix 23, wherein if the weights corresponding to the elevation angle and azimuth angle based on the second positioning signal are greater than or equal to a predetermined value, the positioning device calculates the position information based on the second positioning signal without using the correction information.

[0129] (Note 25) The reference station calculates the difference in the total number of electrons between the total number of electrons in the ionosphere based on the third positioning signal and the total number of electrons in the ionosphere based on the first positioning signal, with respect to the elevation angle information and the azimuth angle information. The positioning program described in Appendix 23, wherein the weight is set to 1 when the total difference in the number of electrons is greater than or equal to a predetermined threshold.

[0130] (Note 26) The aforementioned reference station calculates the total electron count difference amount for the elevation angle information and the azimuth angle information at multiple different time periods. The reference station sets a plurality of weights for each of the total electron count difference amounts in the plurality of different time periods, The positioning program described in Appendix 25, wherein the reference station sets the sum of the plurality of weights to the weights corresponding to the elevation angle information and the azimuth angle information.

[0131] (Note 27) The positioning program described in Appendix 25, wherein the reference station calculates an error between the position information of the evaluation station calculated based on the correction information and the position information of the evaluation station based on the third positioning signal, and updates the predetermined threshold based on the error.

[0132] (Note 28) The reference station notifies the reference station of the identification information of the evaluation station located within a predetermined distance range from the positioning device. The positioning device is a positioning program as described in Appendix 22, which obtains the elevation angle and azimuth angle mask and the correction information for the evaluation station corresponding to the identification information from the reference station. [Explanation of Symbols]

[0133] 1: Positioning system 2: Target Station 3: Reference station 4: Evaluation Bureau 5:Control station 6A:Satellite 6B:Artificial satellite 8: Network 9: Ionosphere 9A:Ionosphere 9B:Ionosphere

Claims

1. A reference station that receives the first positioning signal from an artificial satellite, A target station that receives a second positioning signal from the aforementioned artificial satellite, The reference station generates an elevation-azimuth mask that includes information on the elevation and azimuth of the satellite and determines whether or not to generate correction information, using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the target station and the total number of ionospheric electrons based on the first positioning signal. The reference station generates the correction information using the positioning error based on the first positioning signal. The aforementioned target station is a positioning system that calculates location information based on the second positioning signal, the information, and the correction information corresponding to the elevation angle and azimuth angle.

2. The positioning system according to claim 1, wherein the information included in the elevation angle and azimuth angle mask comprises elevation angle information and azimuth angle information between the reference station and the artificial satellite, and weights corresponding to the elevation angle information and the azimuth angle information.

3. The positioning system according to claim 2, wherein if the weights corresponding to the elevation angle and azimuth angle based on the second positioning signal are greater than or equal to a predetermined value, the target station calculates the position information based on the second positioning signal without using the correction information.

4. The reference station calculates the difference in the total number of electrons between the total number of electrons in the ionosphere based on the third positioning signal and the total number of electrons in the ionosphere based on the first positioning signal, with respect to the elevation angle information and the azimuth angle information. The positioning system according to claim 2, wherein the weight is set to 1 when the total difference in the number of electrons is greater than or equal to a predetermined threshold.

5. The aforementioned reference station calculates the total electron count difference amount for the elevation angle information and the azimuth angle information at multiple different time periods. The reference station sets a plurality of weights for each of the total electron count difference amounts in the plurality of different time periods, The positioning system according to claim 4, wherein the reference station sets the sum of the plurality of weights to the weights corresponding to the elevation angle information and the azimuth angle information.

6. The positioning system according to claim 4, wherein the reference station calculates an error between the position information of the evaluation station calculated based on the correction information and the position information of the evaluation station based on the third positioning signal, and updates the predetermined threshold based on the error.

7. The reference station notifies the reference station of the identification information of the evaluation station located within a predetermined distance from the target station. The positioning system according to claim 1, wherein the target station obtains the elevation angle and azimuth angle mask and the correction information for the evaluation station corresponding to the identification information from the reference station.

8. Acquisition means for acquiring correction information and an elevation angle and azimuth mask including information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite, Receiving means for receiving a second positioning signal from the artificial satellite and acquiring the elevation angle and azimuth angle between the artificial satellite and the positioning device, The system comprises a positioning means that calculates position information based on the second positioning signal, the elevation angle and the azimuth angle, the information of the elevation angle and azimuth angle mask corresponding to the elevation angle and the azimuth angle, and the correction information corresponding to the elevation angle and the azimuth angle, The elevation angle and azimuth angle mask is generated by the reference station using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the positioning device, and the total number of ionospheric electrons based on the first positioning signal. The correction information is generated by the reference station using the positioning error based on the first positioning signal in a positioning device.

9. An acquisition step of obtaining correction information and an elevation angle and azimuth angle mask including information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite, A receiving step of receiving a second positioning signal from the artificial satellite and obtaining the elevation angle and azimuth angle between the artificial satellite and the positioning device, The system comprises a positioning step that calculates position information based on the second positioning signal, the elevation angle and the azimuth angle, the information of the elevation angle-azimuth mask corresponding to the elevation angle and the azimuth angle, and the correction information corresponding to the elevation angle and the azimuth angle, The elevation angle and azimuth angle mask is generated by the reference station using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the positioning device, and the total number of ionospheric electrons based on the first positioning signal. A positioning method in which the correction information is generated by the reference station using the positioning error based on the first positioning signal.

10. An acquisition step of obtaining correction information and an elevation angle and azimuth angle mask including information for determining whether or not to use the correction information from a reference station that receives a first positioning signal from an artificial satellite, A receiving step of receiving a second positioning signal from the artificial satellite and obtaining the elevation angle and azimuth angle between the artificial satellite and the positioning device, The system comprises a positioning step that calculates position information based on the second positioning signal, the elevation angle and the azimuth angle, the information of the elevation angle-azimuth mask corresponding to the elevation angle and the azimuth angle, and the correction information corresponding to the elevation angle and the azimuth angle, The elevation angle and azimuth angle mask is generated by the reference station using the total number of ionospheric electrons based on the third positioning signal received from the satellite by an evaluation station located near the positioning device, and the total number of ionospheric electrons based on the first positioning signal. The correction information is a positioning program generated by the reference station using the positioning error based on the first positioning signal.

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