Positioning device and recording medium

Abstract

To provide a positioning device capable of avoiding failure due to an indirect wave, and achieving accurate positioning.SOLUTION: A positioning device 1 comprises a reception part 10, a prediction pseudo distance calculation part 20, a reliability calculation part 30, and a positioning processing part 40. The prediction pseudo distance calculation part 20 determines a first predicted pseudo distance of a first positioning satellite on the basis of a reception result of a first positioning satellite, and determines a second predicted pseudo distance of a second positioning satellite on the basis of a reception result of a second positioning satellite. The reliability calculation part 30 determines first reliability of the first positioning satellite on the basis of a first difference between the first observed pseudo distance and the first predicted pseudo distance of the first positioning satellite, and determines second reliability of the second positioning satellite on the basis of a second difference between the second observed pseudo distance and the second predicted pseudo distance of the second positioning satellite. The positioning processing part 40 executes positioning processing by reflecting the first reliability and second reliability as weighting information, in residuals of the first positioning satellite and the second positioning satellite.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a positioning device, a recording medium, and the like. [Background technology]

[0002] Patent Document 1 discloses a positioning device that performs positioning by excluding, from among the multiple GPS satellites received, GPS satellites for which there is a large difference between the estimated pseudorange for each GPS satellite and the observed pseudorange. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-112494 A Summary of the Invention [Problem to be solved by the invention]

[0004] According to the positioning device disclosed in Patent Document 1, GPS satellites with large residual errors are not used for positioning, so the number of GPS satellites used for positioning decreases, which may result in a decrease in positioning accuracy. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to a positioning device that includes a receiving unit that receives signals from a first positioning satellite and a second positioning satellite; a predicted pseudorange calculation unit that calculates a first predicted pseudorange of the first positioning satellite based on a reception result of the first positioning satellite, and calculates a second predicted pseudorange of the second positioning satellite based on the reception result of the second positioning satellite; a reliability calculation unit that calculates a first reliability of the first positioning satellite based on a first difference between a first observed pseudorange of the first positioning satellite and the first predicted pseudorange, and calculates a second reliability of the second positioning satellite based on a second difference between a second observed pseudorange of the second positioning satellite and the second predicted pseudorange; and a positioning processing unit that performs positioning processing by reflecting the first reliability and the second reliability as weighting information in the residuals of the first positioning satellite and the second positioning satellite.

[0006] Another aspect of the present disclosure relates to a recording medium having recorded thereon a program that causes a computer to function as a predicted pseudorange calculation unit that calculates a first predicted pseudorange and a second predicted pseudorange of the first positioning satellite and the second positioning satellite based on the reception results of the first positioning satellite and the second positioning satellite, a reliability calculation unit that calculates a first reliability and a second reliability of the first positioning satellite and the second positioning satellite based on a first difference and a second difference between the first observed pseudorange and the second observed pseudorange of the first positioning satellite and the second positioning satellite and the first predicted pseudorange and the second predicted pseudorange, and a positioning processing unit that performs positioning processing by reflecting the first reliability and the second reliability as weighting information in the residuals of the first positioning satellite and the second positioning satellite. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing the configuration of a positioning device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a terminal to which the positioning device of the present embodiment is applied. [Diagram 3] FIG. 13 is a graph showing the relationship between observed pseudoranges and predicted pseudoranges when signal variation is small. [Figure 4] FIG. 13 is a graph showing the relationship between observed pseudoranges and predicted pseudoranges when there is a large signal variation. [Diagram 5] 13 is a diagram for explaining a case where an offset is used in the calculation of a predicted pseudorange. [Figure 6] 5A and 5B are diagrams for explaining the relationship between an estimated distance and an observed distance. [Figure 7] 5 is a flowchart for explaining a process according to the first embodiment of the present invention. [Figure 8] 10 is a flowchart for explaining a process according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present embodiment will be described below. Note that the present embodiment described below does not unduly limit the contents of the claims. Furthermore, not all of the configurations described in the present embodiment are necessarily essential configurations.

[0009] 1. Positioning device 1 is a block diagram showing the configuration of a positioning device 1 according to this embodiment. The positioning device 1 according to this embodiment includes a receiving unit 10, a predicted pseudorange calculation unit 20, a reliability calculation unit 30, and a positioning processing unit 40.

[0010] The receiving unit 10 receives signals transmitted by, for example, GPS (Global Positioning System) satellites. The receiving unit 10 receives signals from, for example, a first positioning satellite and a second positioning satellite (not shown), which are GPS satellites. The signals transmitted by the GPS satellites are received by the receiving unit 10 via a GPS antenna 12, and the receiving unit 10 outputs the received signals to a predicted pseudorange calculation unit 20.

[0011] The predicted pseudo distance calculation unit 20 calculates a predicted value of the pseudo distance between the GPS satellite and the positioning device 1 based on the signal output from the receiving unit 10. The pseudo distance is a distance calculated by multiplying the difference between the time when the radio wave is transmitted from the GPS satellite and the time when the signal is received by the positioning device 1 by the speed of light. The predicted value of the pseudo distance calculated by the predicted pseudo distance calculation unit 20 is called a predicted pseudo distance. For example, when the pseudo distance between the GPS satellite and the positioning device 1 is observed in time series, the predicted pseudo distance is a pseudo distance predicted to be observed at the next observation time. For example, the predicted pseudo distance calculation unit 20 calculates a first predicted pseudo distance, which is a predicted pseudo distance between the first positioning satellite and the positioning device 1, based on the reception result of a first positioning satellite (not shown), and calculates a second predicted pseudo distance, which is a predicted pseudo distance between the second positioning satellite and the positioning device 1, based on the reception result of a second positioning satellite (not shown). The predicted pseudorange calculation unit 20 inputs a signal including information such as the first predicted pseudorange and the second predicted pseudorange to the reliability calculation unit 30. In the following, the first predicted pseudorange and the second predicted pseudorange will be collectively referred to as the predicted pseudorange where appropriate. The pseudorange between the positioning device 1 and each satellite corresponds to the pseudorange between the receiving unit 10 and each satellite, and the position of the positioning device 1 corresponds to the position of the receiving unit 10.

[0012] The reliability calculation unit 30 uses the predicted pseudorange and the observed pseudorange, which is the pseudorange actually observed, to calculate the reliability of the signal received from the GPS satellite. As described above, the pseudorange is a distance calculated by multiplying the difference between the time when the GPS satellite transmits the radio wave and the time when the positioning device 1 receives the signal by the speed of light, but it includes not only the geometric distance between the positioning device 1 and the GPS satellite, but also the influence of the delay of the radio wave from the GPS satellite, the offset and error of the time between the positioning device 1 and the GPS satellite, and the like. The observed pseudorange includes various errors that appear as distance due to such non-geometric factors. Then, when the deviation of the observed pseudorange from the predicted pseudorange calculated by the predicted pseudorange calculation unit 20 is large, or when the variation in the difference of the observed pseudorange from the predicted pseudorange is large, the observed pseudorange includes many errors due to such non-geometric factors. The difference is the difference between the observed pseudorange and the predicted pseudorange at a certain point in time. The reliability is information indicating the magnitude of the difference between the predicted pseudorange and the observed pseudorange, i.e., information indicating the likelihood of the signal received from a GPS satellite. The observed pseudorange between a first positioning satellite (not shown) and the positioning device 1 is called the first observed pseudorange, and the observed pseudorange between a second positioning satellite (not shown) and the positioning device 1 is called the second observed pseudorange. The reliability calculation unit 30 calculates the reliability based on information such as the first predicted pseudorange and the second predicted pseudorange output by the predicted pseudorange calculation unit 20, and the first observed pseudorange and the second observed pseudorange.

[0013] Specifically, the reliability calculation unit 30 obtains a first reliability of the first positioning satellite based on a first difference between the first observed pseudorange and the first predicted pseudorange of the first positioning satellite, and obtains a second reliability of the second positioning satellite based on a second difference between the second observed pseudorange and the second predicted pseudorange of the second positioning satellite. The reliability calculation unit 30 outputs a signal including information such as the first reliability and the second reliability to the positioning processing unit 40. In the following, the first difference and the second difference are collectively referred to as the difference, the first reliability and the second reliability are collectively referred to as the reliability, and the first observed pseudorange and the second observed pseudorange are collectively referred to as the observed pseudorange, as appropriate.

[0014] The positioning processing unit 40 positions the position of the positioning device 1. The positioning processing unit 40 positions the position of the positioning device 1 based on the reliability calculated by the reliability calculation unit 30. For example, the reliability calculation unit 30 calculates the difference between the predicted pseudorange and the observed pseudorange with respect to a certain positioning satellite, and if the calculated difference is large, calculates that the reliability of the positioning satellite is low. In this case, the positioning processing unit 40 uses the calculated reliability to weight the residual so that the residual with the positioning satellite is less likely to be reflected in the positioning, and performs positioning. Also, if the calculated difference is small, the reliability calculation unit 30 calculates that the reliability of the positioning satellite is high, and the positioning processing unit 40 uses the calculated reliability to weight the residual so that the residual with the positioning satellite is reflected in the positioning, and performs positioning. In this way, the positioning processing unit 40 performs positioning processing by reflecting the first reliability calculated by the reliability calculation unit 30 as weighting information on the residual with the first positioning satellite, and reflecting the second reliability as weighting information on the residual with the second positioning satellite.

[0015] Thus, the positioning device 1 of this embodiment includes a receiving unit 10, a predicted pseudorange calculation unit 20, a reliability calculation unit 30, and a positioning processing unit 40. The receiving unit 10 receives signals from a first positioning satellite and a second positioning satellite. The predicted pseudorange calculation unit 20 obtains a first predicted pseudorange of the first positioning satellite based on the reception result of the first positioning satellite, and obtains a second predicted pseudorange of the second positioning satellite based on the reception result of the second positioning satellite. The reliability calculation unit 30 obtains a first reliability of the first positioning satellite based on a first difference between a first observed pseudorange and the first predicted pseudorange of the first positioning satellite, and obtains a second reliability of the second positioning satellite based on a second difference between a second observed pseudorange and the second predicted pseudorange of the second positioning satellite. The positioning processing unit 40 performs positioning processing by reflecting the first reliability and the second reliability as weighting information on the residuals of the first positioning satellite and the second positioning satellite.

[0016] According to this embodiment, the predicted pseudorange calculation unit 20 obtains a first predicted pseudorange and a second predicted pseudorange based on a signal received by the receiving unit 10. The reliability calculation unit 30 calculates a first reliability using a first difference between the first observed pseudorange and the first predicted pseudorange, and a second reliability using a second difference between the second observed pseudorange and the second predicted pseudorange. Then, the positioning processing unit 40 reflects the first reliability and the second reliability as weighting information in the residual with each satellite during positioning processing.

[0017] In this way, it is possible to avoid the effects of the position accuracy of the positioning device 1 and the effects of the signal strength from each satellite being changed by reflected waves from buildings around the positioning device, and to accurately determine the position of the positioning device 1 using the fluctuations in the signals received from each satellite.

[0018] FIG. 2 is a block diagram showing the configuration of a terminal to which the positioning device 1 of the present embodiment is applied. The terminal is, for example, a smart device such as a smartphone or a tablet terminal, or an in-vehicle device. The terminal includes a processing device 2, a GPS antenna 12, and a receiving unit 10. The processing device 2 is, for example, a microcomputer, and includes a processing unit 6 corresponding to a processor, a communication unit 3, the positioning device 1, a memory 4, and an output unit 5. The receiving unit 10 is, for example, a GPS chip that receives a GPS signal and outputs a pseudo distance or the like. In this way, the positioning device 1 can be configured as a terminal by the processing device 2 corresponding to a microcomputer, the receiving unit 10, and the GPS antenna 12. The predicted pseudo distance calculation unit 20, the reliability calculation unit 30, and the positioning processing unit 40 described in FIG. 1 are realized by software processing of the processing unit 6 built into the processing device 2.

[0019] The communication unit 3 performs interface communication between the receiving unit 10 and the processing device 2. The communication unit 3 performs interface communication, for example, to take in and output data in synchronization with a clock signal. As an example, the communication unit 3 can be realized by an interface circuit such as SPI (Serial Peripheral Interface) or I2C (Inter-Integrated Circuit).

[0020] The memory 4 is a storage device that stores various types of information. The processing unit 6 operates based on the information stored in the memory 4, or causes the memory 4 to store various types of information. The memory 4 can be realized by, for example, a semiconductor memory such as a RAM or a ROM.

[0021] The processing unit 6 operates according to a program recorded on a recording medium (not shown). The recording medium has recorded thereon a program for operating a computer as the predicted pseudorange calculation unit 20, the reliability calculation unit 30, and the positioning processing unit 40. That is, the processing unit 6 operates as the predicted pseudorange calculation unit 20, the reliability calculation unit 30, and the positioning processing unit 40 based on the program recorded on the recording medium.

[0022] The receiving unit 10 transmits the signal received from the GPS antenna 12 to the communication unit 3 of the processing device 2. The receiving unit 10 can be realized by, for example, an IC that performs processes such as reception processing of GPS signals. In the processing device 2, the communication unit 3, the positioning device 1, the memory 4, and the output unit 5 are connected to one another via a BUS. The signal input to the communication unit 3 is input to the positioning device 1 via the BUS. In the positioning device 1, the pseudo distance between each satellite and the terminal is measured based on the signal received by the receiving unit 10 and the weighting information described above. The pseudo distance measured in the positioning device 1 is converted into position information, output from the output unit 5, and displayed as a positioning result on the terminal.

[0023] The positioning device 1 of this embodiment can also be realized as a storage medium. Specifically, the recording medium of this embodiment stores a program that causes the processing unit 6, which is a processor, to operate as the predicted pseudorange calculation unit 20, the reliability calculation unit 30, and the positioning processing unit 40. The recording medium can be realized by, for example, a non-volatile memory, an optical disk, or a HDD.

[0024] That is, the recording medium of this embodiment records a program that causes a computer to function as the predicted pseudorange calculation unit 20, the reliability calculation unit 30, and the positioning processing unit 40. The predicted pseudorange calculation unit 20 calculates the first predicted pseudorange and the second predicted pseudorange of the first positioning satellite 101 and the second positioning satellite 102 based on the reception results of the first positioning satellite 101 and the second positioning satellite 102. The reliability calculation unit 30 calculates the first reliability and the second reliability of the first positioning satellite 101 and the second positioning satellite 102 based on the first difference and the second difference between the first observed pseudorange and the second observed pseudorange of the first positioning satellite 101 and the second positioning satellite 102 and the first predicted pseudorange and the second predicted pseudorange. The positioning processing unit 40 can reflect the first reliability and the second reliability as weighting information in the residual of the first positioning satellite 101 and the second positioning satellite 102 during the positioning process. By doing so, it is possible to obtain the same effects as those of the positioning device 1 described above.

[0025] In this embodiment, the positioning device 1 continuously observes the observation information received from each satellite, such as pseudorange and Doppler. Then, the difference between the predicted pseudorange and the observed pseudorange is calculated, and the reliability of the signal received from each GPS satellite is calculated based on this. In this way, it is possible to obtain the reliability of the signal that is independent of the position and signal strength of the positioning device 1. Then, by using this reliability in the positioning calculation, the positioning accuracy is improved.

[0026] As a method for calculating the predicted pseudorange, for example, a method of adding Doppler information and drift information to the initial pseudorange as shown in equation (1) can be used.

[0027]

number

[0028] Doppler information is information such as frequency shift observed by the positioning device 1 due to the relative speed between the GPS satellite and the positioning device 1. For example, when the positioning device 1 is stationary and the GPS satellite is moving, the Doppler information and drift information of the GPS satellite can be used to predict how the pseudorange will change over time. Doppler information is an observed value or a predicted value, and drift information is a calculated value.

[0029] In formula (1), for example, the first observed pseudorange can be used as the initial pseudorange. If the first observed pseudorange obtained for the first positioning satellite is the first initial observed pseudorange, the first predicted pseudorange is obtained by adding Doppler information and drift information to the first initial observed pseudorange as an initial value. The process of calculating the first predicted pseudorange at each time thereafter based on a certain initial value is called the first update process. The above formula (1) is an example of the first update process that employs the process of adding Doppler information and drift information at each time.

[0030] Similarly, if the first observed pseudorange obtained for the second positioning satellite is the second initial observed pseudorange, the second predicted pseudorange is obtained by adding the Doppler information and drift information at each time to the second initial observed pseudorange as an initial value. As with the first update process, the process of calculating the second predicted pseudorange at each subsequent time based on a certain initial value is called the second update process. The first update process and the second update process are not limited to the process shown in equation (1). Moreover, the initial pseudorange in equation (1), i.e., the initial value, is not limited to the first initial observed pseudorange or the second initial observed pseudorange.

[0031] The Doppler information is the observed value of the amount of movement of the GPS satellite. When the positioning device 1 is at a fixed point and not moving, the Doppler information is less susceptible to the effects of multipath. The drift information is the amount of change in the clock deviation of the positioning device 1, and if there is no significant position error, it has little effect on the calculation result of the predicted pseudorange.

[0032] That is, in the positioning device 1 of this embodiment, the predicted pseudorange calculation unit 20 performs a first update process using the first initial observation pseudorange of the first positioning satellite as an initial value to obtain a first predicted pseudorange for each time series, and performs a second update process using the second initial observation pseudorange of the second positioning satellite as an initial value to obtain a second predicted pseudorange for each time series.

[0033] In this manner, the predicted pseudorange calculation unit performs a first update process using the first initial observed pseudorange as an initial value to obtain a first predicted pseudorange for each time series, and the predicted pseudorange calculation unit performs a second update process using the second initial observed pseudorange as an initial value to obtain a second predicted pseudorange for each time series.

[0034] In addition, in the positioning device 1 of this embodiment, the predicted pseudorange calculation unit 20 performs a first update process based on Doppler information between the first positioning satellite and the receiving unit 10 and clock drift information of the receiving unit 10, and performs a second update process based on Doppler information between the second positioning satellite and the receiving unit 10 and clock drift information of the receiving unit 10.

[0035] In this way, the first update process and the second update process can be performed using the Doppler information and the drift information.

[0036] As described above, the difference is the difference between the observed pseudorange and the predicted pseudorange at a certain point in time, and the difference is obtained in a time series, and the reliability based on the variance can be used for the positioning calculation. The variance is, for example, the standard deviation of the difference obtained in the time series, but it may also be the difference between the maximum and minimum values ​​of the difference obtained in the time series.

[0037] 3 and 4 are diagrams showing an example of observed pseudoranges and predicted pseudoranges acquired in a time series. FIG. 3 shows an example of a GPS satellite with a small variation in the difference between the observed pseudorange and the predicted pseudorange. The predicted pseudorange obtained by the above-mentioned calculation method is shown by a dashed line, and the observed pseudoranges actually observed at times t0, t1, t2, . . . , tn are plotted on the horizontal axis. As shown in FIG. 3, when the variation in the difference is small, the deviation of the observed pseudorange is small with respect to the transition of the predicted pseudorange shown by the dashed line. In other words, the observed pseudorange is within a predetermined error with respect to the transition of the predicted pseudorange. In this case, the standard deviation of the "difference", which is the difference between the observed pseudorange and the predicted pseudorange at a certain point in time, or the difference between the maximum value and the minimum value, are both small. Therefore, the reliability of the signal received from the GPS satellite is high.

[0038] Figure 4 shows an example of a GPS satellite with a large variation in the difference between the observed pseudorange and the predicted pseudorange. As shown in Figure 4, when the difference variation is large, the deviation of the observed pseudorange from the transition of the predicted pseudorange shown by the dashed line is large, and the observed pseudorange is outside the specified error range for the transition of the predicted pseudorange. In this case, the standard deviation of the difference or the difference between the maximum and minimum values ​​both become large, and the reliability of the observed pseudorange obtained from the signal received from that GPS satellite becomes low.

[0039] In this way, reliability is an index that indicates the likelihood of a signal received from a GPS satellite, and the greater the variance in the difference, the smaller the reliability becomes, and vice versa. In other words, reliability is inversely correlated with the variance in the difference.

[0040] In the positioning device 1 of this embodiment, the reliability calculation unit 30 calculates a first reliability based on a plurality of first differences obtained in time series, and calculates a second reliability based on a plurality of second differences obtained in time series.

[0041] In this way, the reliability calculation section 30 can obtain the first reliability by obtaining the first differences in time series, and can obtain the second reliability by obtaining the second differences in time series.

[0042] Furthermore, in the positioning device 1 of this embodiment, the reliability calculation unit 30 calculates the first reliability based on the difference between the maximum and minimum values ​​of the multiple first differences or the standard deviation of the multiple first differences, and calculates the second reliability based on the difference between the maximum and minimum values ​​of the multiple second differences or the standard deviation of the multiple second differences.

[0043] In this way, by calculating the difference between the maximum and minimum values ​​of the multiple first differences obtained in a time series, the first reliability can be calculated based on this. Also, by calculating the standard deviation of the multiple first differences, the first reliability can be calculated based on this. And, by calculating the difference between the maximum and minimum values ​​of the multiple second differences obtained in a time series, the second reliability can be calculated based on this. Also, by calculating the standard deviation of the multiple second differences, the second reliability can be calculated based on this.

[0044] FIG. 5 is a diagram showing another example of observed pseudoranges acquired in a time series. The observed pseudoranges shown in FIG. 5 are different from the observed pseudoranges shown in FIG. 3 and FIG. 4 in that the difference between the dashed line indicating the transition of the predicted pseudorange is large at any time, and the variation of the observed pseudorange at each time is small. In such a case, it can be determined that the error of the observed pseudorange is small. That is, it can be determined that the reliability of the signal from the GPS satellite is high. Then, assuming that the initial pseudorange in the calculation formula of the predicted pseudorange shown in Equation (1) is not an appropriate value, an offset correction is performed to increase or decrease the value of the initial pseudorange, which is the initial value. In this case, the predicted pseudorange shown by the dashed line in FIG. 5 becomes like a dashed line shifted by the offset. Then, when the predicted pseudorange after the offset correction is used as a reference, the difference between the observed pseudorange and the predicted pseudorange becomes small, and the variation of the difference also becomes small. In this way, when it is determined that the observed pseudorange does not have an error, the reference of the predicted pseudorange may be changed.

[0045] As described above, the positioning processing unit 40 performs positioning processing by reflecting the first reliability and the second reliability as weighting information on the residual error of the first positioning satellite 101 and the second positioning satellite 102. The residual error is the difference between the observed distance and the estimated distance estimated based on the predicted state of the positioning device 1 (position including the clock error of the satellite and the positioning device).

[0046] 6 shows the observed distance and the estimated distance in the positional relationship between the first positioning satellite 101, the second positioning satellite 102, and the positioning device 1. The positioning device 1 shown in a dashed frame and the distance shown in a dashed line indicate the residual error, which is the difference between the estimated distance and the observed distance.

[0047] In Fig. 6, the observed distance is indicated by a solid line, and the residual, which is the difference between the estimated distance and the observed distance, is indicated by a dotted line. In the positional relationship between the positioning device 1 and each satellite shown in Fig. 6, the first observed distance actually observed as the distance to the positioning processing unit 40 is approximately the same as the first estimated distance estimated as the distance to the positioning processing unit 40, but the second observed distance is smaller than the second estimated distance. The difference between the second observed distance and this second estimated distance is the second residual. In the following, the first estimated distance and the second estimated distance are collectively referred to as the estimated distance, and the first residual and the second residual are collectively referred to as the residual, as appropriate.

[0048] Here, the processing in the positioning device 1 of the present embodiment described above will be explained using mathematical expressions. First, the predicted pseudorange calculation unit 20 obtains a predicted pseudorange based on the signal received by the receiving unit 10. As described above, the predicted pseudorange is a pseudorange predicted to be observed at the next observation time when, for example, the pseudorange between a GPS satellite and the positioning device 1 is observed in time series. The predicted pseudorange is calculated by adding Doppler information and drift information to the initial pseudorange, for example, as shown in equation (1).

[0049] The reliability calculation unit 30 obtains, in a time series manner, the difference between the predicted pseudorange calculated by the predicted pseudorange calculation unit 20 and the actually observed pseudorange, and calculates the reliability based on the variance of the obtained differences.

[0050] Then, the positioning processing unit 40 performs the positioning process by reflecting the reliability calculated by the reliability calculation unit 30 on the residual. As described above, the reliability is inversely correlated with, for example, the variation in the difference.

[0051] The positioning processing unit 40 performs positioning processing by reflecting the reliability as weighting information in the residual for each satellite. Here, the residual is the difference between the estimated distance and the observed distance estimated by the positioning device 1. The residual y is calculated as shown in Equation (2).

[0052]

number

[0053] Here, by multiplying the residual y by the reliability indicating the accuracy of the signal received from the GPS satellite as weighting information, it is possible to determine to what extent the residual y is reflected in the positioning result X in the ECEF coordinates based on the reliability. Here, the weighting information indicating the reliability is K. Moreover, the residual y weighted by the reliability is called a weighted residual vector. By adding the residual vector at time t to the positioning result Xt at time t, the positioning result X at the current time can be obtained as shown in formula (3).

[0054]

number

[0055] As described above, in the positioning device 1 of this embodiment, the positioning processing unit 40 performs positioning processing by weighting the first residual between the first observation distance and the first estimated distance of the first positioning satellite 101 with a first reliability based on the difference between the first observation pseudo distance and the first predicted pseudo distance of the first positioning satellite 101, and weighting the second residual between the second observation distance and the second estimated distance of the second positioning satellite 102 with a second reliability based on the difference between the second observation pseudo distance and the second predicted pseudo distance of the second positioning satellite 102.

[0056] In this way, the residual of the first observed distance from the first estimated distance is weighted according to the first reliability, and the residual of the second observed distance from the second estimated distance is weighted according to the second reliability, thereby enabling positioning processing to be performed with high accuracy, which reflects the reliability of each satellite.

[0057] Here, the problems of the conventional positioning device will be described. In the positioning device disclosed in Patent Document 1, GPS satellites with a large difference between the predicted pseudo distance and the observed pseudo distance are excluded from among the GPS satellites for positioning. In this case, GPS satellites with a large residual error are not used for positioning, so the number of GPS satellites used for positioning is reduced, and there is a risk of the accuracy of positioning being reduced.

[0058] In this regard, the positioning device 1 of the present embodiment calculates the reliability according to the variance of the signal from each GPS satellite, and performs positioning by weighting the residual between the observed distance and the estimated distance. Therefore, unlike the positioning device disclosed in Patent Document 1, the risk of a decrease in positioning accuracy due to a decrease in the number of GPS satellites used for positioning is unlikely to occur.

[0059] It is also known that the accuracy of GNSS positioning decreases in environments such as urban areas where it is difficult to receive GNSS (Global Navigation Satellite System) signals directly and where it is susceptible to the influence of reflected waves from buildings, etc. As a countermeasure, according to a positioning device disclosed in the specification of U.S. Pat. No. 1,112,5886, the positioning device determines the reliability of a signal using a residual error and signal strength calculated based on the position of the receiver. In this case, the estimation of the error of the pseudo-range due to multipath caused by reflected waves, etc. depends on the position that is the premise of the calculation. For this reason, it is difficult to estimate the error of the pseudo-range unless the GNSS receiver is incorporated in a system that can acquire the initial position. In addition, in GNSS receivers that can acquire the initial position, the quality of the GNSS signal is often determined by the strength of the signal, but even if the signal is strong, it may be reinforced by the influence of reflected waves, and this often does not lead to an improvement in the positioning accuracy. In addition, the initial position acquired by the GNSS receiver may be incorrect.

[0060] In this respect, the positioning device 1 of this embodiment does not need to use the position of the GNSS receiver. Therefore, it is possible to estimate the error of the pseudorange without relying on the accuracy of the position information acquired by the GNSS receiver as described above. In addition, the position does not change every time positioning is performed, and it is possible to avoid changing the calculation standard for each positioning.

[0061] In this way, in the positioning device 1 of this embodiment, the reliability of the signal from each GPS satellite is determined independently of the position and signal strength of the positioning device 1, thereby improving the GNSS positioning accuracy and expanding the range of use of the GNSS positioning position.

[0062] The above-mentioned positioning process has been described on the assumption that the positioning device 1 is stationary, but it can also be applied to the case where the positioning device 1 is moving. When the positioning device 1 is moving, a detection unit that detects the movement of the positioning device 1 is provided, and the predicted pseudorange calculation unit 20 calculates the transition of the predicted pseudorange based on the detection result of the detection unit. Specifically, the predicted pseudorange calculation unit 20 calculates the transition of the predicted pseudorange that reflects the angular velocity detected by the detection unit and the inertial information including the angular velocity. Alternatively, it is possible to reflect from the observed pseudorange without providing a sensor such as a detection unit. For example, the predicted pseudorange calculation unit 20 can obtain the relative moving distance between each satellite and the receiving unit 10, and calculate the transition of the predicted pseudorange that reflects the relative moving distance.

[0063] In the above, it has been explained that a reliability corresponding to the variance in the difference for each satellite is calculated and the reliability is used to perform positioning processing, but the variance in the difference may also be used to determine whether or not to use the signal from each satellite for positioning processing.

[0064] 2. Processing example Next, a processing example in the positioning device 1 described above will be described using a flowchart. FIG. 7 is a flowchart for explaining the processing of the first embodiment of the positioning device 1 of this embodiment. First, in step S1, the receiver 10 receives signals from the first positioning satellite 101 and the second positioning satellite 102 from the GPS antenna 12. Steps S2a and S2b are steps for calculating the predicted pseudorange. In step S2a, the predicted pseudorange calculation unit 20 calculates the first predicted pseudorange based on the reception result for the first positioning satellite 101, and in step S2b, the predicted pseudorange based on the reception result for the second positioning satellite 102. In the next steps S3a and S3b, the reliability calculation unit 30 calculates the first reliability based on the first difference between the first observed pseudorange and the first predicted pseudorange in step S3a, and calculates the second reliability based on the second difference between the second observed pseudorange and the second predicted pseudorange in step S3b. Then, step S4 is a step for performing a positioning process, in which the positioning processor 40 performs the positioning process by reflecting the first reliability and the second reliability as weighting information on the residuals of the first positioning satellite 101 and the second positioning satellite 102. In this manner, the positioning result is calculated.

[0065] FIG. 8 is a flow chart for explaining the processing of the second embodiment of the positioning device 1 of this embodiment. In the processing example of the second embodiment, steps S3a and S3b, which are steps for calculating the reliability in the processing example of the first embodiment, are embodied as shown in steps S33a and S33b in FIG. 8. In the second embodiment, the reliability calculation unit 30 calculates the first reliability based on a plurality of first differences obtained in a time series in step S33a. Similarly, in step S33b, the reliability calculation unit 30 calculates the second reliability based on a plurality of second differences. Step S34 is the same as step S4 in the first embodiment shown in FIG. 7.

[0066] Here, in step S4, the positioning processor 40 can perform positioning processing by performing Kalman filter processing using the reliability indicating the variation in the difference between the observed pseudorange and the predicted pseudorange calculated by the reliability calculator 30. In the Kalman filter processing, a current state estimate is obtained from a previous state estimate of a state vector including the positioning position, etc. The state vector includes the position in ECEF (Earth Centered Earth Fixed) coordinates, velocity, bias, drift, etc.

[0067] In the predict part that performs state prediction in the Kalman filter process, prediction of the state vector and covariance is performed. The prediction formula of the state vector is shown in Equation (4). Xt in Equation (4) corresponds to the predicted state vector at the current time t in the Kalman filter process. And Xt-1 corresponds to the state vector at the previous calculation time t-1 in the Kalman filter process. That is, the predicted state vector at the current time t is obtained by calculating the state transition model F on the state vector at the previous calculation time t-1. A stationary model, a constant velocity model, a constant acceleration motion model, or the like can be applied to the state transition model F. In step S4, state prediction based on such a state transition model F is performed in the positioning processing unit 40. The predicted covariance is expressed as shown in Equation (5).

[0068]

number

[0069]

number

[0070] In equation (5), Pt-1 is the covariance at the previous calculation time t-1, F T is the transpose matrix of the state transition model F, and Q is the covariance of the process noise.

[0071] In the correction part, which performs updates in the Kalman filter processing, positioning processing is performed using the residual before positioning and the Kalman gain. If the residual before positioning is y, y is expressed as in equation (6).

[0072]

number

[0073] In equation (6), z is the observed distance from the positioning satellite to the positioning device, which includes errors due to error components caused by the effects of multipath, etc., H is the observation matrix, and Xt is the predicted state vector at time t. The second term obtained by multiplying the observation matrix H by the state vector Xt is the distance estimated at time t. The offset in the third term is the offset amount in the offset correction described in FIG. 5.

[0074] As described above, the positioning processor 40 performs positioning processing by reflecting the reliability of each satellite as weighting information in the residual with each satellite, but when applying Kalman filter processing in step S4, it is possible to use K, which reflects the reliability of each satellite as weighting information. K is expressed as the ratio of the predicted covariance P shown in equation (5) to the covariance S of the residual of the observed value, and is expressed as in equation (7).

[0075]

number

[0076] The covariance S of the observation residuals in the denominator of equation (7) is expressed as in equation (8).

[0077]

number

[0078] R in the second term of formula (8) is the reliability indicating the likelihood of the signal from each satellite. In the second embodiment, this R allows the aforementioned variation in the difference for each satellite to be applied. For example, when the variation in the difference for each satellite is large, R indicating the reliability of formula (8) becomes large, and K shown in formula (7) becomes small. In this manner, K is calculated based on R indicating the reliability. Then, the positioning result X is calculated by using K calculated by formula (7) and the aforementioned formula (3). That is, the positioning result X is calculated by adding y weighted by K reflecting the reliability R to the state vector Xt in the first term on the right side of formula (3).

[0079] In this way, by performing positioning processing using R, which indicates the reliability of the signal from each satellite, the proportion of residual errors caused by inaccurate position information reflected in the positioning can be reduced. This makes it possible to improve the accuracy of positioning performed by the positioning device 1 even when there is a large variation in the difference between the observed pseudorange and the predicted pseudorange. The Kalman filter processing in step S4 described above is performed by the positioning processing unit 40 in the block diagram shown in FIG.

[0080] As described above, in the positioning device 1 of this embodiment, the positioning processing unit 40 sets the reliability indicating the likelihood of the signal from each satellite as weighting information and performs the positioning process.

[0081] In this way, the positioning device 1 can perform positioning by reflecting the reliability calculated by the variance in the difference between the predicted pseudorange and the observed pseudorange through Kalman filter processing as weighting information on the residual, which is the difference between the estimated range and the observed range.

[0082] Furthermore, in step S4, the positioning process can also be performed by performing least squares processing. When the least squares processing without weighting of this embodiment is used, the least squares solution calculated assuming that the error of the signal from each satellite, i.e., the reliability, is the same becomes the positioning result. When the least squares processing is performed in this embodiment, the first reliability of the first positioning satellite 101 is obtained in step S3, and the second reliability of the second positioning satellite 102 is obtained in step S3. Weighting is performed using the reliability obtained in step S3. Equation (9) shows a calculation formula for the positioning result X using the least squares method weighted using the reliability obtained in step S3.

[0083]

number

[0084] H is the observation matrix, W is a weighting matrix that reflects the reliability indicating the likelihood of the signal received from each satellite, and Δr is the residual. When the number of positioning satellites is n, the weighting matrix W is expressed as a matrix with n rows and n columns as shown in equation (10), and Δr is a vector with n rows and 1 column.

[0085]

number

[0086] The variance in the difference between the predicted pseudorange and the observed pseudorange of each satellite, that is, the reliability indicating the likelihood of the signal received from each satellite, is applied to σ1, σ2, ..., σn in equation (10). Alternatively, each diagonal element of the weighting matrix W shown in equation (10) may be a weighted average according to the number of satellites.

[0087] That is, in the positioning device 1 of this embodiment, the positioning processing unit 40 performs positioning processing by least squares processing in which the reliability indicating the likelihood of the signal received from each satellite is set in a weighting matrix.

[0088] In this way, by weighting the signals received from each satellite according to the reliability that indicates the likelihood of the signal being received, it is possible to achieve highly accurate least squares processing.

[0089] As described above, the positioning device of this embodiment includes a receiving unit, a predicted pseudorange calculation unit, a reliability calculation unit, and a positioning processing unit. The receiving unit receives signals from the first positioning satellite and the second positioning satellite. The predicted pseudorange calculation unit calculates a first predicted pseudorange of the first positioning satellite based on the reception result of the first positioning satellite, and calculates a second predicted pseudorange of the second positioning satellite based on the reception result of the second positioning satellite. The reliability calculation unit calculates a first reliability of the first positioning satellite based on a first difference between a first observed pseudorange and the first predicted pseudorange of the first positioning satellite, and calculates a second reliability of the second positioning satellite based on a second difference between a second observed pseudorange and the second predicted pseudorange of the second positioning satellite. The positioning processing unit performs positioning processing by reflecting the first reliability and the second reliability as weighting information on the residuals of the first positioning satellite and the second positioning satellite.

[0090] According to this embodiment, the predicted pseudorange calculation unit calculates the first predicted pseudorange and the second predicted pseudorange based on the signal received by the receiving unit, and the positioning processing unit reflects, as weighting information, the first reliability calculated by the reliability calculation unit using the first difference between the first observed pseudorange and the first predicted pseudorange and the second reliability calculated by the reliability calculation unit using the second difference between the second observed pseudorange and the second predicted pseudorange on the residuals of the first positioning satellite and the second positioning satellite.

[0091] In this way, it is possible to avoid the effects of the position accuracy of the positioning device and the effects of the strength of the signals from each satellite being changed by reflected waves from buildings and the like around the positioning device, and to accurately determine the position of the positioning device from the fluctuations in the signals received from each satellite.

[0092] In the positioning device of this embodiment, the predicted pseudorange calculation unit performs a first update process using the first initial observation pseudorange of the first positioning satellite as an initial value to obtain a first predicted pseudorange for each time series, and performs a second update process using the second initial observation pseudorange of the second positioning satellite as an initial value to obtain a second predicted pseudorange for each time series.

[0093] In this manner, the predicted pseudorange calculation unit performs a first update process using the first initial observed pseudorange as an initial value to obtain a first predicted pseudorange for each time series, and the predicted pseudorange calculation unit performs a second update process using the second initial observed pseudorange as an initial value to obtain a second predicted pseudorange for each time series.

[0094] In the positioning device of this embodiment, the predicted pseudorange calculation unit performs a first update process based on Doppler information between the first positioning satellite and the receiving unit and clock drift information of the receiving unit, and performs a second update process based on Doppler information between the second positioning satellite and the receiving unit and clock drift information of the receiving unit.

[0095] In this way, the first update process and the second update process can be performed using the Doppler information and the drift information.

[0096] In the positioning device of this embodiment, the reliability calculation unit calculates a first reliability based on a plurality of first differences obtained in time series, and calculates a second reliability based on a plurality of second differences obtained in time series.

[0097] In this way, the first reliability can be obtained by obtaining the first differences in time series, and the second reliability can be obtained by obtaining the second differences in time series.

[0098] In the positioning device of this embodiment, the reliability calculation unit calculates the first reliability based on the difference between the maximum and minimum values ​​of the multiple first differences or the standard deviation of the multiple first differences, and calculates the second reliability based on the difference between the maximum and minimum values ​​of the multiple second differences or the standard deviation of the multiple second differences.

[0099] In this way, by calculating the difference between the maximum and minimum values ​​of the multiple first differences obtained in a time series, the first reliability can be calculated based on this. Also, by calculating the standard deviation of the multiple first differences, the first reliability can be calculated based on this. And, by calculating the difference between the maximum and minimum values ​​of the multiple second differences obtained in a time series, the second reliability can be calculated based on this. Also, by calculating the standard deviation of the multiple second differences, the second reliability can be calculated based on this.

[0100] In the positioning device of this embodiment, the positioning processing unit weights a residual vector including a first residual between the first observation distance and the first estimated distance of a first positioning satellite and a second residual between the second observation distance and the second estimated distance of a second positioning satellite based on a weighting matrix, which is weighting information in which a first reliability is set to a first element and a second reliability is set to a second element, and performs positioning processing using the weighted residual vector.

[0101] In this way, the residual of the first observed distance from the first estimated distance is weighted according to the first reliability, and the residual of the second observed distance from the second estimated distance is weighted according to the second reliability, thereby enabling positioning processing to be performed, thereby obtaining highly accurate positioning results.

[0102] In the positioning device of this embodiment, the positioning processing unit performs Kalman filtering to perform positioning processing.

[0103] In this way, the positioning result can be calculated by Kalman filter processing.

[0104] In the positioning device of this embodiment, the positioning processing unit reflects a Kalman gain calculated based on the first reliability and the second reliability in the residual between the first positioning satellite and the second positioning satellite.

[0105] In this way, the state vector can be updated by reflecting the Kalman gain calculated based on the first reliability and the second reliability as weighting information in the residual of the pseudorange of each satellite.

[0106] In the positioning device of this embodiment, the positioning processing unit performs the positioning process by a least squares method process in which weighting information is set in a weighting matrix.

[0107] In this way, by performing weighting using the weighting information, it is possible to realize highly accurate least squares processing.

[0108] The recording medium of this embodiment records a program that causes a computer to function as a predicted pseudorange calculation unit, a reliability calculation unit, and a positioning processing unit. The predicted pseudorange calculation unit calculates a first predicted pseudorange and a second predicted pseudorange of the first positioning satellite and the second positioning satellite based on the reception results of the first positioning satellite and the second positioning satellite. The reliability calculation unit calculates a first reliability and a second reliability of the first positioning satellite and the second positioning satellite based on a first difference and a second difference between the first observed pseudorange and the second observed pseudorange of the first positioning satellite and the first predicted pseudorange and the second predicted pseudorange. The positioning processing unit performs positioning processing by reflecting the first reliability and the second reliability as weighting information on the residual of the first positioning satellite and the second positioning satellite.

[0109] Although the present embodiment has been described in detail as above, it will be easily understood by those skilled in the art that many modifications are possible without substantially departing from the novel matters and effects of the present disclosure. Therefore, all such modifications are intended to be included in the scope of the present disclosure. For example, a term described at least once in the specification or drawings together with a different term having a broader meaning or synonymy may be replaced with that different term anywhere in the specification or drawings. In addition, all combinations of the present embodiment and modifications are also included in the scope of the present disclosure. In addition, the configurations and operations of the positioning device and the recording medium are not limited to those described in the present embodiment, and various modifications are possible. [Explanation of symbols]

[0110] 1...positioning device, 2...processing device, 3...communication unit, 4...memory, 5...output unit, 10...receiving unit, 12...GPS antenna, 20...predicted pseudorange calculation unit, 30...reliability calculation unit, 40...positioning processing unit, 76...interface circuit, 101...first positioning satellite, 102...second positioning satellite, H...observation matrix, K...weighting information, P...covariance, R, S...covariance, S1, S21, S22a, S22b, S23a, S24a, S2a, S2b, S33a, S33b, S34, S3a, S3b, S4, S43a, S43b...step, t, t-1...time, W...weighting matrix, X...positioning result, Xt, Xt-1...state vector, y...residual

Claims

1. a receiving unit for receiving signals from a first positioning satellite and a second positioning satellite; a predicted pseudorange calculation unit that calculates a first predicted pseudorange of the first positioning satellite based on a reception result of the first positioning satellite, and calculates a second predicted pseudorange of the second positioning satellite based on the reception result of the second positioning satellite; a reliability calculation unit that calculates a first reliability of the first positioning satellite based on a first difference between a first observed pseudorange and the first predicted pseudorange of the first positioning satellite, and calculates a second reliability of the second positioning satellite based on a second difference between a second observed pseudorange and the second predicted pseudorange of the second positioning satellite; a positioning processing unit that performs a positioning process by reflecting the first reliability and the second reliability as weighting information on residuals of the first positioning satellite and the second positioning satellite; A positioning device comprising:

2. 2. The positioning device according to claim 1, The predicted pseudorange calculation unit performing a first update process using a first initial observed pseudorange of the first positioning satellite as an initial value to obtain the first predicted pseudorange for each time series; A positioning device characterized in that the second predicted pseudorange is calculated for each time series by performing a second update process using a second initial observed pseudorange of the second positioning satellite as the initial value.

3. 3. The positioning device according to claim 2, The predicted pseudorange calculation unit performing the first update process based on Doppler information between the first positioning satellite and the receiving unit and drift information of a clock of the receiving unit; A positioning device, comprising: a positioning unit configured to perform the second update process based on the Doppler information between the second positioning satellite and the receiving unit, and the drift information of the clock of the receiving unit.

4. 3. The positioning device according to claim 2, The reliability calculation unit is determining the first reliability based on a plurality of the first differences obtained in time series; The positioning device, comprising: a positioning unit that calculates the second reliability based on a plurality of the second differences obtained in the time series.

5. 5. The positioning device according to claim 4, The reliability calculation unit is determining the first reliability based on a difference between a maximum value and a minimum value of the plurality of first differences or a standard deviation of the plurality of first differences; The positioning device, comprising: a positioning unit that calculates the second reliability based on a difference between the maximum value and the minimum value of the plurality of second differences, or based on the standard deviation of the plurality of second differences.

6. 2. The positioning device according to claim 1, The positioning processing unit includes: a residual vector including a first residual between a first observation range and a first estimated range of the first positioning satellite and a second residual between a second observation range and a second estimated range of the second positioning satellite, weighting based on a weighting matrix, which is the weighting information in which the first reliability is set to a first element and the second reliability is set to a second element; A positioning device, characterized in that the positioning process is performed using the weighted residual vector.

7. 2. The positioning device according to claim 1, The positioning processing unit includes: A positioning device, comprising: a Kalman filter process for performing the positioning process.

8. 8. The positioning device according to claim 7, The positioning processing unit includes: A positioning device, comprising: a Kalman gain calculated based on the first reliability and the second reliability, the Kalman gain being reflected in a residual between the first positioning satellite and the second positioning satellite.

9. 2. The positioning device according to claim 1, The positioning processing unit includes: The positioning device performs the positioning process by a least squares method process in which the weighting information is set in a weighting matrix.

10. a predicted pseudorange calculation unit that calculates a first predicted pseudorange and a second predicted pseudorange of the first positioning satellite and the second positioning satellite based on reception results of the first positioning satellite and the second positioning satellite; a reliability calculation unit that calculates a first reliability and a second reliability of the first positioning satellite and the second positioning satellite based on a first difference and a second difference between a first observed pseudorange and a second observed pseudorange of the first positioning satellite and the second positioning satellite and the first predicted pseudorange and the second predicted pseudorange; a positioning processing unit that performs positioning processing by reflecting the first reliability and the second reliability as weighting information on residuals of the first positioning satellite and the second positioning satellite, A recording medium having a program recorded thereon for causing a computer to function.

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