JP6440217B1 - Method and apparatus for correcting positioning error in satellite navigation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve positioning accuracy by reducing positioning error of propagation delay due to ionosphere in an area where ionospheric fluctuation is large.
When creating the correction information of propagation delay due to the ionosphere transmitted from the master station to the user station, the ionospheric storm monitor determines whether or not the ionospheric delay amount data conforms to the ionosphere model. While it is determined that it is not suitable, the number of data of the ionospheric delay amount is sequentially reduced and then re-determined, and it is created from the ionospheric delay amount at the time when it is determined that it is compatible. The user station corrects the positioning signal from the navigation satellite using the propagation delay correction information by the ionosphere, and performs positioning of the own station.
[Selection] Figure 1

Description

  The present invention relates to a positioning error correction method and apparatus in a satellite navigation system, and more particularly to a positioning error correction method and apparatus in a wide area differential correction system (hereinafter referred to as WADGPS). .

  In general, electromagnetic waves (hereinafter referred to as signals) emitted from artificial satellites and celestial bodies pass through the ionosphere and troposphere before reaching the ground, but a delay occurs when signals pass through the respective regions. These delays are called ionospheric delay and tropospheric delay, respectively. Therefore, when this signal is used as a positioning signal, these ionospheric delay and tropospheric delay are one of the positioning error sources.

  For the user station, which is a receiver that the user has, not only correction of ionospheric delay, which is one of the causes of positioning errors, but also correction information corresponding to other error factors is provided. The method of reducing the positioning error by performing the correction process is referred to as a wide-area differential correction method (WADGPS). As an example of WADGPS, there is a satellite based augmentation system (hereinafter referred to as SBAS) that is being put into practical use worldwide.

  In WADGPS, the goal is to separately correct positioning error sources such as satellite orbits, satellite clocks, ionospheric delays, and tropospheric delays with high accuracy. The satellite clock is affected regardless of where the user is, but the satellite orbit (satellite position), ionospheric propagation delay, and tropospheric propagation delay differ depending on the position of the receiver (user station). It is. By correcting all of these positioning error sources separately and sending different correction information depending on the position, differential correction effective in a wide geographical range is possible.

  Conventionally, as a system for performing such differential correction, there are satellite navigation systems shown in FIGS. 4 and 5 as described in Patent Document 1, Patent Document 2, and Patent Document 3.

  4 and 5, 151 (151a, 151b...) Is a monitor station, and the position is known for the purpose of improving the positioning accuracy by the positioning signal from the navigation satellite 152 (152a, 152b...). A plurality of locations are installed at certain known points. The monitor station 151 (151a, 151b...) Has a network 153, and is connected to the master station 154 via the network 153. Reference numeral 155 denotes a user station that is a receiver of the user.

  The navigation satellites 152 (152a, 152b...) Are GPS satellites, and each transmits detailed orbit information of the GPS satellites at two frequencies (L1: 1.6 GHz band / L2: 1.2 GHz band). ing. Since the ionospheric delay has a characteristic that it varies depending on the frequency of the signal, the ionospheric delay can be obtained by calculation using measurement data of two frequencies received at the monitor station.

  The monitor station 151 (151a, 151b...) Has a two-frequency GPS receiver capable of receiving positioning signals transmitted from GPS satellites at two frequencies (L1, L2). Data is transmitted to the master station 154 via the network 153.

  The master station 154 has a function of obtaining an ionospheric delay amount from measurement data of a positioning signal received from the navigation satellite received by the monitor station, and an IGP (Ionospheric Grid) set every 5 degrees in longitude and latitude using this ionospheric delay amount. (Point: ionosphere grid point, hereinafter referred to as IGP) is used to calculate the ionospheric delay, and to create the grid information that is the correction information, to create the correction information of the orbit of the navigation satellite, and to be transmitted from the navigation satellite And a function of transmitting the generated correction information (grid information, trajectory correction information, clock correction information) to the user station 155.

  The user station 155 normally has a single-frequency GPS receiver that can receive a positioning signal transmitted from a GPS satellite for only one frequency (L1), and corrects it using correction information from the master station 154. By doing so, it has a function that can improve positioning accuracy.

  4 and 5, the monitor station 151 (151a, 151b...) Is a positioning signal transmitted from the navigation satellite 152 (152a, 152b...), A quasi-zenith satellite, or a geostationary satellite (not shown). The measurement data is transmitted to the master station 154 via the network 153.

  The master station 154 calculates an ionospheric delay amount, which is a propagation delay due to the ionosphere, based on the measurement data of the two-frequency GPS receiver included in each monitor station 151 (151a, 151b...) (FIGS. 4161 and 5171). ). Since the ionospheric delay amount calculated in the master station 154 is calculated using the measurement data of the two-frequency GPS receiver, the measurement error is small and the accuracy is high. Next, the master station 154 uses this ionosphere delay amount to calculate model parameters based on the ionosphere model, thereby obtaining ionosphere delay amounts in each IGP, and creates grid information that is correction information (FIG. 4). 162). This grid information is coarsened to be transmitted to the user station 155, and is created for each IGP.

  Next, the master station 154 creates navigation satellite orbit correction information using the ionospheric delay amount (FIG. 4163), and further creates positioning signal clock correction information transmitted from the navigation satellite (FIG. 4163). FIG. 4 164).

  The master station 154 transmits the correction information (grid information, orbit correction information, clock correction information) thus created to the user station 155 via the geostationary satellite (FIG. 4165).

  The user station 155 receives the correction information (grid information, orbit correction information, clock correction information) transmitted from the master station 154 and performs correction processing (FIG. 4166). That is, the correction information is used to correct the ionospheric propagation delay in the user station 155, the orbit of the navigation satellite, and the clock of the positioning signal from the navigation satellite.

  Regarding the correction of the ionospheric propagation delay, the grid information transmitted from the master station 154 is linearly interpolated using the grid information of four IGPs adjacent to the point where the positioning signal passes through the ionosphere. The ionospheric delay amount is obtained and corrected (FIG. 5 172). In this way, the user station 155 corrects the ionospheric propagation delay, the satellite orbit, the satellite clock, and performs positioning of the user station 155.

JP 2007-171082 A JP 2011-203100 A Japanese Patent Laying-Open No. 2015-138021

  However, in a wide area differential correction system such as SBAS as before, four error factors are reliably separated, and how to reduce the positioning error due to these four error factors when positioning at the user station, It was an important issue.

  In particular, in the ionosphere (D, E, F layer) existing in the upper atmosphere, disturbance phenomena of various scales occur in time and space, and the radio waves of satellite communication are greatly affected. And since solar ultraviolet rays and X-rays received by the atmosphere change depending on the season, latitude / longitude, time, solar activity cycle, etc., the ionosphere basically changes depending on these. In addition to these steady changes, the ionosphere also has an increase in X-rays and high-energy particles due to sudden solar explosions, disturbances such as magnetic storms typified by aurora activity, or disturbances in the medieval atmosphere as the host. It changes complicatedly under the influence of. In some cases, a disturbance state called an ionospheric storm occurs. In such a case, it is difficult to accurately correct the propagation delay of the ionosphere. For this reason, there is a problem that positioning errors that cannot be completely corrected remain. For example, in the southern region of Japan, especially in the south of Kyushu, there is a problem that the ionospheric fluctuation is large, so that errors due to ionospheric propagation delay cannot be corrected and sufficient positioning accuracy cannot be obtained.

  As a method for solving such a problem, it is conceivable that the ionospheric delay amount is corrected by the two-frequency data in the user station as in the master station. However, if the GPS receiver of the user station is a two-frequency GPS receiver similar to the monitor station, the size of the antenna increases, and two sets of high-frequency circuits are required, resulting in increased costs. . In addition, the receiver mounted on the aircraft has a problem that, for safety reasons, only a single frequency GPS receiver can be used.

  Thus, the conventional ionospheric propagation delay correction information cannot be corrected, and the positioning error cannot be reduced. Therefore, there has been a demand for new correction information for the ionospheric propagation delay that can minimize this positioning error.

  In addition, in the next MSAS, there is a plan to add a vertical guidance function, and improvement of availability by improving a correction information generation method for ionospheric propagation delay is an urgent issue, and an immediate solution to the problem is required.

  The invention according to claim 1 obtains the correction information of the clock of the positioning signal, the correction information of the orbit of the navigation satellite, and the correction information of the propagation delay due to the ionosphere from the positioning signal from the navigation satellite. A master station that transmits to a user station, which is a receiver that the user has, a plurality of monitor stations installed at known points, receiving a positioning signal from a navigation satellite in order to obtain correction information thereof, and a master station In a satellite navigation system consisting of a network connecting multiple monitor stations, the master station uses the positioning signals from all the navigation satellites that can be received by the monitor station to determine the ionospheric delay, which is the propagation delay due to the ionosphere. The ionospheric delay collected to create this correction information when creating the correction information for the propagation delay due to the ionosphere that can be used by the user station from the ionospheric delay amount However, if the ionosphere storm monitor determines whether the ionosphere model conforms to the ionosphere model used to create the ionospheric propagation delay correction information, and if it does not conform to the ionosphere model, the ionospheric propagation delay correction information Reduce the number of ionospheric delay data collected to create and re-determine with the ionospheric storm monitor, and while it is determined that the ionospheric delay data does not fit the ionosphere model, If the number of delay data is further reduced and then re-determined and it is determined that the ionosphere model is met, the ionospheric propagation delay that can be used by the user station is corrected from the ionospheric delay at this point. The master station then creates the ionospheric propagation delay correction information along with the clock correction information and the orbit correction information. This user station receives positioning signals from a plurality of receivable navigation satellites, and these positioning signals are transmitted from the master station as propagation delay correction information by the ionosphere, clock correction information, This is a method for correcting a positioning error in a satellite navigation system, in which correction is performed based on orbit correction information and positioning of a user station is performed.

  The invention according to claim 2 is the invention according to claim 1, wherein the ionosphere storm monitor makes a determination using a chi-square test.

  The invention according to claim 3 is the invention according to any one of claims 1 to 2, wherein when the ionospheric delay amount data is reduced, the ionospheric delay amount at a point far from the point at which the correction information of the propagation delay by the ionosphere is created. The data is reduced in order of distance from the data.

  According to a fourth aspect of the invention, in the invention according to any one of the first and second aspects, when the ionospheric delay amount data is reduced, the ionospheric delay amount data at a point close to the equator is reduced in descending order of latitude. Is.

  The invention according to claim 5 is the invention according to any one of claims 1 to 3, wherein when reducing the ionospheric delay amount data, the distance from the point where the correction information for propagation delay due to the ionosphere is created to the farthest point is set. With respect to the collection range as the radius, an upper limit is set in the range where the collection range is narrowed by reducing the data.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, when the ionospheric delay amount data is reduced, an upper limit is provided for the number of data to be reduced.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the propagation delay correction information by the ionosphere is information for each grid point created every 5 degrees longitude and latitude.

  The invention according to claim 8 obtains correction information of the clock of the positioning signal, correction information of the orbit of the navigation satellite, and correction information of the propagation delay due to the ionosphere based on the positioning signal from the navigation satellite. A master station that transmits to a user station, which is a receiver that the user has, a plurality of monitor stations installed at known points, receiving a positioning signal from a navigation satellite in order to obtain correction information thereof, and a master station In a satellite navigation system consisting of a network connecting a plurality of monitor stations, the master station has a function to obtain an ionospheric delay amount that is a propagation delay by the ionosphere using positioning signals from all navigation satellites that can be received by the monitor station; From the ionospheric delay amount, when the correction information of the propagation delay due to the ionosphere that can be used by the user station is created, the power collected to create the correction information is collected. If the ionospheric storm monitor has a function to determine whether or not the ionospheric delay is compatible with the ionosphere model used to create correction information for propagation delay due to the ionosphere, Decrease the number of ionospheric delay data collected to create propagation delay correction information and re-determine with the ionospheric storm monitor. The user station uses the ionospheric delay amount at this point if it determines that it is compatible with the ionospheric model and the function to repeat the determination after further reducing the number of ionospheric delay amount data Function to create possible ionospheric propagation delay correction information, ionospheric propagation delay correction information, clock correction information, and orbit correction information Both of them have a function of transmitting to a user station, and the user station receives a positioning signal from a plurality of receivable navigation satellites and a propagation delay due to the ionosphere transmitted from the master station. This is a device for correcting a positioning error in a satellite navigation system, which has a function of performing correction by each of correction information, clock correction information, and orbit correction information, and positioning a user station.

  The invention according to claim 9 is the invention according to claim 8, wherein the ionospheric storm monitor has a function of performing determination using a chi-square test.

  The invention according to claim 10 is the invention according to any one of claims 8 to 9, wherein when the master station reduces the ionospheric delay amount data, the master station is a point far from the point where the correction information for the propagation delay caused by the ionosphere is created. It has a function of decreasing in order from the ionospheric delay data.

  The invention according to claim 11 is the invention according to any one of claims 8 to 9, wherein when the master station reduces the ionospheric delay amount data, the latitude from the ionospheric delay amount data at a point close to the equator is in ascending order of latitude. It has a function to reduce.

  The invention according to claim 12 is the invention according to any one of claims 8 to 10, wherein when the master station reduces the ionospheric delay amount data, the master station is the farthest point from the point where the correction information for the propagation delay caused by the ionosphere is created. As for the collection range whose radius is the distance up to, it has a function of setting an upper limit to the narrowing range of the collection range narrowed by reducing the data.

  The invention according to claim 13 is the invention according to any one of claims 8 to 12, wherein the master station has a function of setting an upper limit to the number of data to be reduced when reducing the data of the ionospheric delay amount.

  The invention according to claim 14 is the invention according to any one of claims 8 to 13, wherein the propagation delay correction information by the ionosphere is information for each grid point created every 5 degrees longitude and latitude.

  Since the invention according to claims 1 and 8 is configured as described above, it is possible to reduce the possibility that the correction error inherent in the correction information of the propagation delay caused by the ionosphere, that is, the residual becomes excessive. In addition, the accuracy of the propagation delay correction information due to the ionosphere is improved, the positioning error due to WADGPS (Wide Area Differential Correction System) can be reduced, and the positioning accuracy is improved. In particular, it is possible to greatly improve the positioning accuracy of WADGPS in a low-latitude region that is easily affected by the ionosphere.

  In addition, the positioning error in the user station can be reduced without changing the hardware configuration of the master station and monitor station in the conventional satellite navigation system, and without changing the hardware and software of the user station. The positioning accuracy can be further improved.

  Since the inventions according to claims 2 and 9 are configured as described above, the same effects as the inventions according to claims 1 and 8 are obtained.

  Since the inventions according to claims 3 and 10 are configured as described above, the same effects as the inventions according to claims 1 and 8 are obtained.

  Since the inventions according to claims 4 and 11 are configured as described above, the same effects as the inventions according to claims 1 and 8 are obtained. Furthermore, since the measurement data at points susceptible to the influence of ionospheric disturbances caused by ionospheric storms is reduced, the effect can be exhibited without reducing the number of measurement data more than necessary.

  Since the inventions according to claims 5 and 12 are configured as described above, the same effects as the inventions according to claims 1 and 8 are obtained. Furthermore, it is possible to reduce the burden on the master station related to the processing of the present invention by limiting the range for narrowing the collection range.

  Since the inventions according to claims 6 and 13 are configured as described above, the same effects as the inventions according to claims 1 and 8 are obtained. Furthermore, by setting a limit on the number of data to be reduced, it is possible to reduce the burden on the master station related to the processing of the present invention.

  Since the inventions according to claims 7 and 14 are configured as described above, the same effects as the inventions according to claims 1 and 8 are obtained.

1 shows a first embodiment of the present invention and is a schematic diagram for explaining a positioning method in a satellite navigation system of the present invention. FIG. FIG. 1 shows a first embodiment of the present invention, and is a schematic diagram for explaining the principle of a positioning method in the satellite navigation system of the present invention, where (a) does not use the positioning method of the present invention; ) Is a diagram when the positioning method of the present invention is used. It is a histogram which shows the effect of this invention and shows the estimation result of the ionospheric delay amount in each IGP. It is a schematic diagram for demonstrating the positioning method in the conventional satellite navigation system. It is a schematic diagram for demonstrating the positioning method in the conventional satellite navigation system.

  A positioning signal from the navigation satellite is used to obtain the correction information of the clock of the positioning signal, the correction information of the orbit of the navigation satellite, and the correction information of the propagation delay due to the ionosphere, and the user has the correction information. A master station to be transmitted to the user station, a network that receives positioning signals from navigation satellites to obtain these correction information, and a network connecting a plurality of monitor stations installed at known points and the master station and the plurality of monitor stations In the satellite navigation system, the master station uses the positioning signals from all the navigation satellites that can be received by the monitor station to obtain ionospheric delay amounts that are propagation delays by the ionosphere, and from these ionospheric delay amounts, the user station When creating correction information for propagation delay due to the ionosphere that can be used by the ionosphere, the amount of ionospheric delay collected to create this correction information The ionosphere storm monitor is used to determine whether the ionosphere model is used to create the correction information for the ionosphere, and if it is determined not to be compatible with the ionosphere model, it is collected to create correction information for propagation delay due to the ionosphere. Decrease the number of ionospheric delay data and make another determination with the ionospheric storm monitor. While it is determined that the ionospheric delay data is not compatible with the ionosphere model even if the ionospheric delay data is reduced, the number of ionosphere delay data If it is determined that it is compatible with the ionosphere model, the correction information of the propagation delay due to the ionosphere that can be used by the user station is created from the ionosphere delay amount at this point, Next, the master station transmits the propagation delay correction information by the ionosphere to the user station together with the clock correction information and the orbit correction information. , Receiving positioning signals from a plurality of receivable navigation satellites, and each of these positioning signals by means of ionospheric propagation delay correction information, clock correction information and orbit correction information transmitted from the master station, respectively. Correct and perform positioning of the user station.

A first embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 shows a first embodiment of the present invention and is a schematic diagram for explaining a positioning method in the satellite navigation system of the present invention. FIG. 2 shows a first embodiment of the present invention and is a schematic diagram for explaining the principle of the positioning method in the satellite navigation system of the present invention. FIG. 2 (a) does not use the positioning method of the present invention. In this case, (b) is a figure when the positioning method of the present invention is used, and how it is affected when creating ionospheric correction information in an area affected by ionospheric disturbances due to ionospheric storms. And how the invention avoids the effects.

  In FIG. 1, 1 (1a, 1b,...) Is a monitor station, and a plurality of locations whose positions are known are for the purpose of improving the positioning accuracy by the positioning signals from the navigation satellite 2 (2a, 2b...). Each is installed at a known point. The monitor station 1 (1a, 1b...) Has a network 3 and is connected to the master station 4 via the network 3. Reference numeral 5 denotes a user station, which is a receiver that the user has.

  The navigation satellite 2 (2a, 2b...) Is a GPS satellite in this embodiment, and detailed orbit information of the GPS satellite itself is stored in two frequencies (L1: 1.6 GHz band / L2: 1.2 GHz band). )

  The monitor station 1 (1a, 1b...) Has a two-frequency GPS receiver capable of receiving a positioning signal transmitted from a GPS satellite with two frequencies (L1, L2). The signal is transmitted to the master station 4 via the network 3.

  The master station 4 obtains ionospheric delay amounts using positioning signals from all navigation satellites received by the monitor station, and obtains ionospheric propagation delay correction information for each navigation satellite using the ionospheric delay amounts. And ionospheric propagation delay correction information in IGP (Ionospheric Grid Point, hereinafter referred to as IGP) set every 5 degrees in longitude and latitude using this ionospheric propagation delay correction information. A function to create grid information (for each navigation satellite), a function to determine the quality of ionospheric propagation delay correction information in this grid information by obtaining the estimation accuracy of the ionospheric delay amount, and navigation satellite orbit correction information , A function to create clock correction information for positioning signals transmitted from navigation satellites, and these correction information ( It has at least a function of transmitting grid information (for each navigation satellite), orbit correction information, and clock correction information to the user station 5.

  The user station 5 has a GPS receiver capable of receiving a positioning signal transmitted from a GPS satellite, and a function that can improve positioning accuracy by correcting using the correction information from the master station 4. have.

  Next, the operation will be described with reference to FIGS.

  The monitor station 1 (1a, 1b...) Receives a positioning signal transmitted from the navigation satellite 2 (2a, 2b...), A signal from a quasi-zenith satellite or a geostationary satellite (not shown), The measurement data is transmitted to the master station 4 via the network 3.

  The master station 4 has a propagation delay due to the ionosphere in each monitor station 1 (1a, 1b,...) Based on the measurement data of the two-frequency GPS receiver that each monitor station 1 (1a, 1b...) Has. The ionospheric delay amount is calculated (FIG. 11) and navigation satellite orbit correction information is created (FIG. 112), and then positioning signal clock correction information transmitted from the navigation satellite is created (FIG. 1). 13). Since the ionospheric delay amount calculated in the master station 4 is calculated using the measurement data of the two-frequency GPS receiver, the measurement error is small and the accuracy is high.

  Then, the master station 4 uses these ionospheric delay amounts to calculate model parameters based on the ionospheric model used for estimating the ionospheric delay amount, thereby estimating the ionospheric delay amount in each IGP, and correcting information thereof. Is created (FIG. 114 (14a, 14b...)). When creating this grid information, it is determined by an ionospheric storm monitor algorithm (hereinafter simply referred to as an ionospheric storm monitor) whether the actual ionospheric state is compatible with the ionospheric model (FIG. 117). When this ionospheric storm monitor is activated, that is, when it is determined that the ionospheric storm monitor is abnormal, the number of ionospheric delay data used to create correction information is reduced (FIG. 118), and the model parameters are calculated again. To do. The model parameter recalculated by reducing the number of data is determined again by the ionospheric storm monitor (FIG. 117), and if it is still determined to be “abnormal”, the ionospheric delay used for creating correction information is further determined. Repeat the process of reducing the amount of data (FIG. 118) and recalculating the model parameters. When the ionospheric storm monitor does not operate, that is, when the ionospheric storm monitor determines that “no abnormality”, the ionospheric delay amount in the IGP is obtained using the model parameters at this time, and grid information is created. . In this way, grid information is created for all IGPs. In this embodiment, since the grid information is broadcast to the user station 5, the accuracy is reduced and the amount of information is suppressed.

  The grid information created in this way is transmitted from the master station 4 to the user station 5 together with other correction information (such as navigation satellite orbit correction information and navigation satellite clock correction information) created by the master station 4. (FIG. 115). The user station 5 can improve the positioning accuracy by performing correction processing using the received correction information (FIG. 116).

  Here, the principle of the present invention when creating grid information in each IGP will be described in detail with reference to FIGS. In FIG. 2, the center of the figure indicates the position of the point 21 of the IGP for which grid information is to be created. When calculating the model parameters in this IGP, among the data of the ionospheric delay amount in each monitor station 1 (1a, 1b...), 22 indicates the data used for the calculation (the portion of ●), and 23 indicates the calculation. Data that is not used (circled part) is shown. In FIG. 2, 24 is the minimum range of the collection range set when collecting the data 22 used for calculation, 25 is the maximum range, and 26 is the range for collecting data. 27 is a region affected by ionospheric disturbances caused by ionospheric storms, and 28 is a measurement data group affected by ionospheric disturbances. By applying this invention, it is no longer used for calculation of model parameters. Measurement data group, that is, a reduced measurement data group.

  First, each monitor station 1 (1a, 1b...) Obtained from the measurement data (positioning signal from the navigation satellite 2 (2a, 2b...)) At each monitor station 1 (1a, 1b...). Are collected in ascending order from the ionospheric delay data of the monitor station 1 (1a, 1b,...) At a location close to the IGP location 21. The number of data to be collected is collected so as to be a maximum of 30 from the viewpoint of safety. When the data in the minimum range 24 of the collection range is less than 30, the collection range 26 is expanded in a range not exceeding the maximum range 25 of the collection range, and the data is collected so as to become 30 pieces. In this embodiment, the minimum range 24 of the collection range has a radius of 800 (km) around the point 21 of the IGP, and the maximum range 25 has a radius of 2100 (km).

  Next, the master station 4 obtains model parameters based on the ionosphere model using the collected data 22, estimates the ionospheric delay amount at the IGP point 21 using the model parameters, and estimates the ionospheric delay amount. Find accuracy. Moreover, the grid information which is the correction information is created by the estimated ionospheric delay amount in the IGP. The grid information broadcast to the user station 5 also includes information on the estimation accuracy of the residual, that is, the ionospheric delay amount at the point 21 of the IGP used to create this grid information. Information is also broadcast to the user station 5.

  When creating this grid information, the master station 4 determines whether or not the actual ionospheric state is compatible with the ionosphere model used for the calculation by the ionosphere storm monitor. This ionospheric storm monitor collects measurement data used for this calculation, that is, data on the ionospheric delay amount of the monitor station 1 (1a, 1b...) Used for the calculation when obtaining model parameters by the ionosphere model. The positioning data is used to determine whether or not the positioning data is affected by disturbance caused by ionospheric storms. In this embodiment, chi-square test is used for the ionospheric storm monitor, and it is determined whether the distribution of the measurement data 22 in the collection range 26 is substantially the same as the distribution of theoretical values. It is configured to operate by outputting “Yes”.

  When the ionospheric storm monitor is activated, that is, when “abnormal” is output, as shown in FIG. 2A, the ionospheric storm is affected by the ionospheric storm in the measurement data collection range. Since the measurement data of the region 27 is included (FIG. 2 (b) 28), the measurement data deviates from the theoretical value distribution. Therefore, if the ionospheric storm monitor is activated and outputs “abnormal”, the model parameter is not compatible because some or all of the collected measurement data does not match the ionosphere model used to calculate the model parameters. It becomes abnormal. With this abnormal model parameter, grid information with poor estimation accuracy is created. Therefore, assuming that the estimation accuracy of the ionospheric delay amount in the IGP used to create the grid information is poor (in this embodiment, information relating to the estimation accuracy is set to the maximum), the information is transmitted to the user station 5 together with the grid information. Was.

  Therefore, in the present invention, when the ionospheric storm monitor is activated, the measurement data collected in order of distance from the IGP is reduced so as to narrow the measurement data collection range 26 used for the calculation, thereby reducing the number of measurement data used for the calculation (FIG. 1 18). Using the measurement data with the reduced number of data, model parameters are obtained again based on the ionosphere model, and are determined again by the ionosphere storm monitor (FIG. 117). If the ionosphere storm monitor still operates even if it is determined again, the measurement data is further reduced (FIG. 118), the model parameters are similarly determined, and the ionospheric storm monitor is determined again (FIG. 117). It is configured to repeat.

  When the ionospheric storm monitor does not operate as a result of reducing the number of measurement data in this manner, that is, when the ionospheric storm monitor determines that “no abnormality”, as shown in FIG. In addition, the measurement data 28 in the region affected by the ionospheric disturbance due to the ionospheric storm is not included by reducing the measurement data, and grid information with high estimation accuracy is created using normal model parameters. That is, if the ionospheric storm monitor determines that there is no abnormality, the measurement data that does not match the ionosphere model used to calculate the model parameter is removed, the model parameter becomes normal, and the grid information is calculated from the ionospheric delay at this point. Therefore, it is possible to create grid information with good estimation accuracy.

  In this embodiment, when the ionospheric storm monitor is activated, there is a restriction on the range for narrowing the collection range 26 when the measurement data is reduced. In this embodiment, the radius to be narrowed is 600 from the narrower range of the collection range when the measurement data collected for obtaining the model parameters reaches 30 pieces or the maximum range 25 of the collection range. It is limited to be (km) or less. However, the present invention is not limited to this. For example, it may be configured to be narrowed to the minimum range 24 of the collection range.

  There is also a limit on the number of data to be reduced when the ionospheric storm monitor is activated. In this embodiment, the number of data to be reduced is limited to a range not exceeding 10. However, the present invention is not limited to this. For example, the configuration is such that even if the number of data to be reduced exceeds 10, the processing can be continued as it is, and finally the minimum number of data to be collected is 10. You may comprise so that the number of data can be reduced.

  In this embodiment, when the ionospheric storm monitor is activated, the ionospheric storm monitor is still activated even if the data is reduced to the lower limit or the collection range is narrowed to the lower limit or the number of data is reduced to the lower limit. Discarding a series of processes of reducing the measurement data in the invention and re-determining with the ionospheric storm monitor, using 30 measurement data collected when creating grid information, obtaining model parameters based on the ionosphere model, By using this model parameter, the ionospheric delay amount in the IGP is estimated to generate grid information. Since this grid information is created with the ionospheric storm monitor in operation, it is grid information with poor estimation accuracy. The information regarding the estimation accuracy of the ionospheric delay amount broadcasted to the user station 5 together with the grid information has a low estimation accuracy, that is, the information regarding the estimation accuracy is set to the maximum.

  In this embodiment, when the ionospheric storm monitor is activated, when the measurement data is reduced, the measurement data is reduced in order of increasing distance from the target IGP. Anyway. As described above, the ionospheric fluctuations are large in the southern region of Japan, particularly in the south of Kyushu. This is due to ionospheric disturbances caused by ionospheric storms, and there is a high probability that ionospheric disturbances due to ionospheric storms will occur in areas south of Japan, in other words, in low latitude areas. Therefore, a more efficient effect can be obtained if the measurement data at points susceptible to the influence of the ionospheric disturbance, that is, the measurement data at the low latitude points are sequentially reduced.

A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 3 shows the effect of the present invention, and is a histogram showing the estimation result of the ionospheric delay amount in each IGP.

  In the second embodiment of the present invention, a simulation performed by the inventor to confirm the effect of the present invention and the result thereof will be described. The same parts as those in the first embodiment are denoted by the same names and the same numbers, and the description thereof is omitted.

  The inventor created correction information for propagation delay due to the ionosphere with (1) the conventional method and (2) the method according to the present invention when 13 monitor stations were arranged for the purpose of assuming SBAS around Japan. At this time, simulation was performed to determine what the ionospheric delay amount estimation result would be, that is, what would be the information regarding the estimation accuracy of the ionospheric delay amount in each IGP. The simulation result is shown in FIG.

  In FIG. 3, the horizontal axis represents an index of GIVE values (GIVEI: Grid Ionical Vertical Error Index), and the vertical axis represents the relative frequency (relative frequency) of GIVEI, that is, the frequency of appearance of GIVEI. In FIG. 3, the black bar indicates the results of (1) the conventional method, and the white bar indicates the result of (2) the method according to the present invention. The index of the GIVE value before and after the application of the method of the present invention is shown. The frequency of appearance is shown respectively.

  A GIVE (Grid Ionospheric Vertical Error) value is a residual of the ionospheric delay amount in each IGP, that is, an estimation error of the ionospheric delay amount in each IGP, and the GIVEI is obtained using this GIVE value as an index. This GIVEI is information related to the estimation accuracy described in the first embodiment, and is information on a 4-bit value broadcast accompanying the ionospheric delay amount correction information broadcast to the user station. GIVEI is a 4-bit value, but GIVEI = 15, that is, the index 15 is a value meaning “unusable”. The maximum value that is set when the ionospheric storm monitor described in the first embodiment is activated is GIVEI = 14, that is, index 14.

  Further, in FIG. 3, (2) the result in the case of the method according to the present invention shows the result when the present invention is applied with the radius of the collection range being limited to 600 (km) or less. Yes.

  As is apparent from FIG. 3, (1) compared to the conventional method, (2) the frequency of appearance of the index 14 by the method according to the present invention is greatly reduced, and conversely, the frequency of appearance of the indexes 11 to 13 is increased. Yes. From this, it can be seen that the frequency of appearance of the index 14 is greatly reduced by the application of the present invention, and the decrease is moved to the indexes 11 to 13. This indicates that the positioning accuracy is reduced because the estimation error of the ionospheric delay amount is reduced by the application of the present invention. Therefore, by applying the present invention, positioning accuracy can be improved and accurate estimation can be performed.

  The correction method in the satellite navigation system according to the present invention can be used for a positioning system of a moving body, a guidance system, and the like. Since the positioning accuracy of the user station is improved, the utilization rate of the navigation mode with vertical guidance can be improved. The spread of SBAS can be expected by improving the utilization rate of the navigation mode with vertical guidance.

  It can also be applied to the quasi-zenith satellite system being developed by the Japan Aerospace Exploration Agency. In particular, in the quasi-zenith satellite submeter-class positioning correction service, positioning accuracy in the south of Kyushu is not sufficient at present, and this improvement is a major issue, but it can be used in this region.

  Furthermore, the next MSAS has a plan to add a vertical guidance function. Since the addition of the vertical guidance function is assumed six years later, it is an urgent need to improve availability by improving the correction information generation method for the ionospheric propagation delay, and the present invention is highly likely to be used.

1 (1a, 1b...) Monitor station 2 (2a, 2b...) Navigation satellite 3 Network 4 Master station 5 User station 17 Ionospheric storm monitor 26 Collection range

Claims (14)

Based on the positioning signal from the navigation satellite, the correction information of the clock of the positioning signal, the correction information of the orbit of the navigation satellite, and the correction information of the propagation delay due to the ionosphere are obtained, and the correction information is received by the receiver that the user has. A master station that transmits to a user station;
In order to obtain the correction information, a positioning signal is received from the navigation satellite, and a plurality of monitor stations installed at known points;
In a satellite navigation system comprising a network connecting the master station and the plurality of monitor stations,
The master station obtains an ionospheric delay amount that is a propagation delay by the ionosphere using positioning signals from all navigation satellites that can be received by the monitor station,
From these ionospheric delay amounts, when creating correction information for propagation delay due to the ionosphere that can be used by the user station, the ionospheric delay amount collected to create this correction information is the correction information for propagation delay due to the ionosphere. The ionosphere storm monitor determines whether the ionosphere model used to create the
When it is determined that the ionosphere model is not adapted, the ionosphere delay amount collected to create the propagation delay correction information by the ionosphere is reduced, and the ionosphere storm monitor determines again, and While it is determined that the ionospheric delay amount data is reduced and the ionosphere model is not adapted to the ionosphere delay amount, the number of data of the ionospheric delay amount is further reduced and then it is determined again.
If it is determined that the ionosphere model is met, the ionospheric delay amount at this point is used to create correction information for propagation delay due to the ionosphere available to the user station,
Then, the master station transmits the propagation delay correction information by the ionosphere to the user station together with the clock correction information and the orbit correction information,
This user station receives positioning signals from a plurality of receivable navigation satellites, and these positioning signals are transmitted from the master station, the propagation delay correction information by the ionosphere, the clock correction information, A method for correcting a positioning error in a satellite navigation system, wherein correction is performed based on the correction information of the orbit and positioning of the user station is performed. The positioning error correction method in the satellite navigation system according to claim 1, wherein the ionospheric storm monitor performs determination using chi-square test. 3. The method according to claim 1, wherein when the ionospheric delay amount data is reduced, the ionosphere delay amount data is decreased in order from the ionospheric delay amount data at a point far from a point where the propagation delay correction information by the ionosphere is created. A method for correcting a positioning error in the satellite navigation system according to claim 1. 3. The positioning in the satellite navigation system according to claim 1, wherein when the ionospheric delay amount data is reduced, the ionospheric delay amount data at a point close to the equator is reduced in descending order of latitude. Error correction method. When reducing the data of the ionospheric delay amount, the collection range whose radius is the distance from the point where the correction information of the propagation delay caused by the ionosphere is created to the farthest point is reduced to a range narrowed by reducing the data. An upper limit is provided. The positioning error correction method in the satellite navigation system according to any one of claims 1 to 3. The method for correcting a positioning error in a satellite navigation system according to any one of claims 1 to 5, wherein when the ionospheric delay amount data is reduced, an upper limit is set for the number of data to be reduced. The positioning error in the satellite navigation system according to any one of claims 1 to 6, wherein the correction information of the propagation delay due to the ionosphere is information for each grid point created every 5 degrees longitude and latitude. Correction method. Based on the positioning signal from the navigation satellite, the correction information of the clock of the positioning signal, the correction information of the orbit of the navigation satellite, and the correction information of the propagation delay due to the ionosphere are obtained, and the correction information is received by the receiver that the user has. A master station that transmits to a user station;
In order to obtain the correction information, a positioning signal is received from the navigation satellite, and a plurality of monitor stations installed at known points;
In a satellite navigation system comprising a network connecting the master station and the plurality of monitor stations,
The master station has a function of obtaining an ionospheric delay amount that is a propagation delay by the ionosphere using positioning signals from all navigation satellites that can be received by the monitor station;
From these ionospheric delay amounts, when creating correction information for propagation delay due to the ionosphere that can be used by the user station, the ionospheric delay amount collected to create this correction information is the correction information for propagation delay due to the ionosphere. An ionospheric storm monitor having a function of determining whether or not the ionosphere model is used to create
When it is determined that the ionosphere model is not adapted, the ionosphere delay amount collected to create the propagation delay correction information by the ionosphere is reduced, and the ionosphere storm monitor determines again, and While it is determined that the ionosphere delay amount data is not adapted to the ionosphere model even if the ionosphere delay amount data is reduced, the function of repeating the determination again after further reducing the number of data of the ionosphere delay amount, and
When it is determined that the ionosphere model is adapted, from the ionospheric delay amount at this point, a function of creating propagation delay correction information by the ionosphere available to the user station,
A function of transmitting propagation delay correction information by the ionosphere to the user station together with the clock correction information and the orbit correction information,
The user station has a function of receiving positioning signals from a plurality of receivable navigation satellites, a correction information of propagation delay due to the ionosphere transmitted from the master station, and a correction information of the clock. And a correction function for the positioning error in the satellite navigation system. The apparatus corrects the positioning error in the satellite navigation system. The apparatus for correcting a positioning error in the satellite navigation system according to claim 8, wherein the ionospheric storm monitor has a function of performing a determination using a chi-square test. When the master station reduces the ionospheric delay amount data, the master station has a function of decreasing in order from the ionospheric delay amount data at a point far from the point where the propagation delay correction information by the ionosphere is created. The apparatus which correct | amends the positioning error in the satellite navigation system in any one of Claims 8-9. The master station has a function of reducing the ionospheric delay amount data from the ionospheric delay amount data at a point close to the equator in order of increasing latitude when reducing the ionospheric delay amount data. The device which corrects the positioning error in the satellite navigation system described in 1. When the master station reduces the ionospheric delay amount data, the collection range narrowed by reducing the data for the collection range having a radius from the point where the propagation delay correction information by the ionosphere is created to the farthest point is reduced. The apparatus for correcting a positioning error in a satellite navigation system according to any one of claims 8 to 10, wherein the apparatus has a function of setting an upper limit in a range to be narrowed. The positioning error in the satellite navigation system according to any one of claims 8 to 12, wherein the master station has a function of setting an upper limit to the number of data to be reduced when the ionospheric delay amount data is reduced. Device to correct. The positioning error in the satellite navigation system according to any one of claims 8 to 13, wherein the correction information of the propagation delay due to the ionosphere is information for each grid point created every 5 degrees longitude and latitude. Device to correct.

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