Positioning device

Abstract

To perform relative positioning where position accuracy in relative positioning is not easily deteriorated on a receiver side even when quality of observation information to be transmitted from a reference station is deteriorated.SOLUTION: A satellite evaluation value is determined by evaluation as a combination of signal intensity of a radio wave (positioning signal) received by a reference station with an elevation angle in a receiver about a satellite that has transmitted the radio wave (positioning signal). Based on the satellite evaluation value, a reference satellite in calculating a double difference of observation data in relative position calculation is selected among the plurality of satellites.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a positioning device, and more particularly to a technique for receiving ranging signals transmitted from satellites of a global positioning satellite system and performing relative positioning using observation data from an observation station and observation data from a reference station. [Background technology]

[0002] Global navigation satellite systems (GNSS: abbreviation for Global Navigation Satellite System), including GPS (abbreviation for Global Positioning System), are a system that calculates the position of a receiving point using radio waves (specifically, ranging signals) transmitted from satellites. Positioning devices that use the global navigation satellite system to measure position and direction, etc., measure the position and direction of the positioning device based on the signals transmitted from multiple satellites.

[0003] As a conventional technology for performing relative positioning using GNSS, a positioning system is known that has multiple positioning means that perform positioning using positioning information transmitted from multiple satellites in the same combination, and determines the distance between the multiple positioning means by taking the difference between the positioning results from the multiple positioning means (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-287850 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, a GNSS receiver that determines centimeter-level positions receives ranging signals transmitted from satellites, and performs relative positioning calculations using information from the ranging signals received by the observation station itself and information from the reference station to determine the position. To determine a highly accurate position, it is necessary to use high-quality information, and in the relative positioning method, both the observation amount obtained by the observation station itself receiving the ranging signal and the observation amount of the reference station must be of high quality. However, depending on the location and installation method of the reference station, the reference station may be blocked. In such cases, the signal strength of the satellite received by the reference station decreases, and errors and noise are superimposed on the observation information. In that case, the relative positioning is performed using the observation information of the reference station to which errors and noise have been added, which results in a problem of a decrease in the position accuracy of the relative positioning.

[0006] Therefore, an object of the present invention is to provide a positioning device that can perform relative positioning with little deterioration in the position accuracy of the relative positioning on the receiver side even when the observation information transmitted from the reference station becomes of low quality. [Means for solving the problem]

[0007] In order to solve the above problem, the present invention provides a positioning device in which a reference station and a receiver receive ranging signals transmitted from a plurality of satellites and calculate a relative position of the receiver with respect to the reference station, and the signal strength of the ranging signals received by the reference station and 、 an elevation angle at the receiver with respect to a satellite that transmitted the ranging signal; a state variable representing a definite state of a half wavelength of the phase of the ranging signal of the satellite from which the receiver has received a radio wave; A reference satellite for calculating the double difference of the observation data in the calculation of the relative position is selected from the plurality of satellites based on an evaluation value determined by evaluating the combination of the above. death , The evaluation value is calculated according to E=C×Ib_j+Ar_j+G×Qr_j (where E: satellite evaluation value, Ib_j: signal strength [dB / Hz] of the ranging signal of the satellite Sj received by the reference station, Ar_j: elevation angle [rad] at the receiver for the satellite Sj that transmitted the ranging signal, Qr_j: status flag indicating the determined state of the half wavelength of the phase of the ranging signal of the satellite Sj received by the receiver, which is a value of 1 corresponding to the determined state or a value of 0 corresponding to the undetermined state, C: coefficient, G: coefficient, and subscript j: satellite Sj). It is characterized by: Effect of the Invention

[0010] According to the invention described in claim 1, a reference satellite is selected from among multiple satellites from which the reference station receives ranging signals based on an evaluation value determined by comprehensively evaluating a combination of the signal strength of the ranging signal and the elevation angle of the satellite at the receiver (in other words, the observation station). Therefore, a high-quality satellite taking into account the radio wave environment at both the reference station and the receiver (observation station) is selected as the reference satellite, and good observation data can be obtained as a result of double difference calculation based on the reference satellite. Even if the signal strength of the satellite received by the reference station decreases and the observation information transmitted from the reference station becomes of low quality, it is possible to perform relative positioning with less deterioration in the positioning accuracy of the relative positioning on the receiver side.

[0011] Claim 1 According to the invention described in the above, the evaluation value can be appropriately determined, and it is possible to more accurately perform relative positioning on the receiver side with less deterioration in the position accuracy of the relative positioning. [Brief description of the drawings]

[0012] [Figure 1] 1 is a functional block diagram showing a schematic configuration of a GNSS receiver including a positioning device according to an embodiment of the present invention. [Diagram 2] 2 is a flow diagram showing a processing procedure in the GNSS receiver of FIG. 1. [Diagram 3] 3 is a flow diagram showing a processing procedure in a reference station satellite determination unit, and is a flow diagram showing details of the processing of step S5 in the flow diagram of FIG. 2. [Figure 4] 3 is a flow diagram showing a processing procedure in a signal strength verification unit, and is a flow diagram showing details of the processing of step S7 in the flow diagram of FIG. 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described below based on the illustrated embodiment. Fig. 1 is a functional block diagram showing a schematic configuration of a GNSS receiver 1 including a positioning device 8 according to an embodiment of the present invention. Fig. 2 is a flow diagram showing a processing procedure in the GNSS receiver 1 according to the embodiment. The processing procedure shown in the flow diagram of Fig. 2 is mainly processing content executed by the positioning device 8 according to, for example, a program, and is repeatedly executed at a predetermined time interval.

[0014] The GNSS receiver 1 is a mechanism for acquiring position information by using a global navigation satellite system (GNSS: Global Navigation Satellite System). The GNSS receiver 1 has a GNSS antenna 2, a GNSS receiving unit 3, a data communication antenna 4, a data receiving unit 5, a satellite information acquiring unit 6, a reference station information acquiring unit 7, and a positioning device 8. The GNSS receiver 1 calculates and outputs its own position relative to other GNSS receivers.

[0015] In the other GNSS receivers mentioned above, the reference station positioned as the "reference station" in the calculation of the relative position (i.e., relative positioning) is fixedly installed and its installation position is determined in advance (i.e., its installation position is known).

[0016] The GNSS antenna 2 receives radio waves (ranging signals; specifically, signals in which a PRN (pseudo-random noise) code and a navigation message are superimposed on a carrier wave (i.e., a carrier) of a predetermined frequency) transmitted from each of a number of satellites (e.g., GPS satellites) and transfers them to the GNSS receiver 3.

[0017] Here, the multiple satellites that constitute the global positioning satellite system and transmit radio waves (ranging signals) received by the GNSS receiver 1 and the reference station are referred to as "multiple satellites Sx." When the multiple satellites Sx are to be distinguished from one another (in other words, when they are meant to be mutually different satellites), the subscript x is changed. Specifically, for example, "satellite Sj" and "satellite Sk" indicate that they are mutually different satellites.

[0018] The GNSS receiver 3 performs a predetermined process on the ranging signal transferred from the GNSS antenna 2 and outputs a signal in a format usable by the satellite information acquisition unit 6. For example, the GNSS receiver 3 converts the frequency of the ranging signal transferred from the GNSS antenna 2 to an intermediate frequency, performs an analog-to-digital conversion process to generate a digital signal, performs a demodulation process on the digital signal, and outputs the demodulated ranging signal (step S1).

[0019] The data communication antenna 4 receives data transmitted from the reference station and transfers it to a data receiving unit 5. Signals are transmitted and received between the GNSS receiver 1 and the reference station in accordance with a predetermined format.

[0020] The data transmitted from the reference station includes radio waves (ranging signals; specifically, signals in which a PRN (pseudo-random noise) code and a navigation message are superimposed on a carrier wave (i.e., a carrier) of a predetermined frequency) transmitted from each of the multiple satellites Sx and received by the reference station via the GNSS antenna. The data transmitted from the reference station and received by the data communication antenna 4 of the GNSS receiver 1, including the ranging signals for each of the multiple satellites Sx received by the reference station, is called "reference station satellite information." The reference station satellite information is transmitted from the reference station at predetermined intervals and supplied to the GNSS receiver 1 (step S2).

[0021] The data receiving unit 5 performs a predetermined process on the data (that is, the reference station satellite information) transferred from the data communication antenna 4, and outputs a signal in a format that can be used by the reference station information acquiring unit .

[0022] The satellite information acquisition unit 6, the reference station information acquisition unit 7, and the positioning device 8 are configured within an arithmetic unit including, for example, a CPU (short for Central Processing Unit), memory, and input / output ports, and the CPU performs the necessary processing by referring to control programs and various data stored in the memory.

[0023] The satellite information acquisition unit 6 uses the ranging signal output from the GNSS receiver unit 3 at each predetermined period, and performs conventionally known arithmetic processing on the ranging signal as necessary to acquire, for each of the multiple satellites Sx, information about the ranging signal and the satellite that transmitted the ranging signal (referred to as "observation station observation data") (step S3).

[0024] The satellite information acquisition unit 6 acquires, as observation station observation data for each of the multiple satellites Sx, for example, the signal strength (dB / Hz; specifically, the carrier power-to-noise ratio, which is the noise power per 1 Hz band) of the ranging signal received via the GNSS antenna 2, the phase of the ranging signal (in other words, the carrier phase), the elevation angle of the satellite that transmitted the ranging signal, and the three-dimensional position (x, y, z) of the satellite that transmitted the ranging signal.

[0025] The reference station information acquisition unit 7 uses information relating to the ranging signal received by the reference station, which is included in the reference station satellite information output from the data receiving unit 5 at each predetermined period, and performs conventionally known arithmetic processing on the ranging signal as necessary to acquire information (referred to as "reference station observation data") relating to the ranging signal received by the reference station and the satellite that transmitted the ranging signal for each of the multiple satellites Sx (step S4).

[0026] The reference station information acquisition unit 7 acquires, as reference station observation data for each of the multiple satellites Sx from which the reference station has received radio waves (ranging signals), for example, the signal strength (dB / Hz) of the ranging signal received by the reference station, the phase of the ranging signal (in other words, the carrier phase), the elevation angle of the satellite that transmitted the ranging signal, and the three-dimensional position (x, y, z) of the satellite that transmitted the ranging signal.

[0027] The observation data from the observation station and the reference station are synchronized for necessary items as necessary using GPS time or the like.

[0028] Note that some or all of the above-mentioned reference station observation data may be calculated in the reference station, and then included in the reference station satellite information and transmitted from the reference station to the GNSS receiver 1.

[0029] The positioning device 8 is a mechanism for calculating the relative position between the GNSS receiver 1 (in other words, the observation station) including the positioning device 8 and the reference station (i.e., the relative position of the observation station with respect to the reference station) based on ranging signals transmitted from multiple satellites Sx, and is equipped with a reference station satellite determination unit 81, a reference satellite selection unit 82, a signal strength verification unit 83, a real solution calculation unit 84, and an integer solution calculation unit 85.

[0030] The reference station satellite determination unit 81 determines whether or not to use the reference station observation data of each of the multiple satellites Sx from which the reference station has received radio waves (ranging signals) for the relative positioning process (step S5). Figure 3 is a flow diagram showing the processing procedure in the reference station satellite determination unit 81, and is a flow diagram showing the details of the processing of step S5 in the flow diagram of Figure 2.

[0031] In this embodiment, the reference station satellite judgment unit 81 determines not to use a ranging signal for calculating the relative position when the difference between the signal strength of the radio waves (ranging signals) received by the GNSS receiver 1 and the signal strength of the radio waves (ranging signals) received by the reference station is equal to or greater than the signal strength difference threshold, and the signal strength of the radio waves (ranging signals) received by the reference station is less than the elevation angle-corresponding signal strength threshold determined corresponding to the elevation angle of the satellite.

[0032] The reference station satellite determination unit 81 first calculates the difference ΔI_j1 between the signal strength (dB / Hz) Ir_j1 of the ranging signal in the observation station observation data and the signal strength (dB / Hz) Ib_j1 of the ranging signal in the reference station observation data for the L1 wave (i.e., a carrier wave with a frequency of 1575.42 MHz) transmitted from a satellite Sj among the multiple satellites Sx, according to the following formula 1 (step S5-1). (Equation 1) ΔI_j1 = Ir_j1-Ib_j1 Here, ΔI_j1: Difference in satellite signal strength for L1 wave of satellite Sj Ir_j1: Signal strength of L1 wave from satellite Sj received by GNSS receiver 1 [dB / Hz] Ib_j1: Signal strength of L1 wave from satellite Sj received by the reference station [dB / Hz] Subscript j1: represents the L1 wave of satellite Sj. The subscript r: represents the GNSS receiver 1 (observation station). Subscript b: denotes reference station.

[0033] The reference station satellite determination unit 81 then determines whether or not the calculated satellite signal strength difference ΔI_j1 for the L1 wave is equal to or greater than the signal strength difference threshold Tid (step S5-2).

[0034] The signal strength difference threshold Tid is a threshold for determining whether the signal strength of the radio wave (ranging signal) of the satellite Sj received by the reference station is significantly lower than the signal strength of the radio wave (ranging signal) of the satellite Sj received by the GNSS receiver 1 to such an extent that the position accuracy of the relative positioning may be significantly reduced. The signal strength difference threshold Tid is not limited to a specific value, and is appropriately set to an appropriate value while taking into consideration that the above-mentioned determination can be performed appropriately. The signal strength difference threshold Tid may be set to any value within a range of about 5 to 15 [dB], for example, and may be set to a value of about 10 [dB] in particular.

[0035] Then, if the satellite signal strength difference ΔI_j1 for the L1 wave is equal to or greater than the signal strength difference threshold Tid (step S5-2: Yes), the reference station satellite determination unit 81 determines whether the signal strength (dB / Hz) Ib_j1 of the ranging signal of the L1 wave in the reference station observation data is equal to or greater than the elevation angle-corresponding signal strength threshold Tie (step S5-3).

[0036] The elevation angle-based signal strength threshold Tie is a threshold for determining whether or not the signal strength expected (in other words, expected) corresponding to the elevation angle of the satellite is ensured when the radio wave environment is good. The elevation angle-based signal strength threshold Tie is determined so that the signal strength increases as the elevation angle of the satellite increases. The relationship between the elevation angle-based signal strength threshold Tie and the signal strength is not limited to a specific relationship, and an appropriate relationship is appropriately set, taking into consideration that the above-mentioned determination can be made appropriately.

[0037] Then, if the signal strength (dB / Hz) Ib_j1 of the ranging signal of the L1 wave among the reference station observation data is equal to or greater than the elevation angle corresponding signal strength threshold Tie (step S5-3: Yes), and if the satellite signal strength difference ΔI_j1 for the L1 wave is less than the signal strength difference threshold Tid (step S5-2: No), the reference station satellite determination unit 81 classifies the L1 wave of the satellite Sj as a satellite signal wave to be used for the relative positioning process (specifically, for example, the value of the utilization flag of the L1 wave of the satellite Sj is set to 1) (step S5-4). Then, the reference station satellite determination unit 81 advances the relative positioning process procedure to the process of step S5-5.

[0038] On the other hand, if the signal strength (dB / Hz) Ib_j1 of the ranging signal of the L1 wave among the reference station observation data is less than the elevation angle-corresponding signal strength threshold Tie (step S5-3: No), the reference station satellite judgment unit 81 does not classify the L1 wave of the satellite Sj as a satellite signal wave to be used for relative positioning processing (specifically, for example, by setting the value of the utilization flag of the L1 wave of the satellite Sj to 0), and proceeds with the relative positioning processing procedure to processing of step S5-5.

[0039] In addition, when the signal strength (dB / Hz) Ib_j1 of the ranging signal of the L1 wave among the reference station observation data is less than the elevation angle corresponding signal strength threshold Tie (step S5-3: No), the observation noise variance value R, which is the diagonal value of the observation noise covariance matrix Rε(n) of the Kalman filter described later, is set to be relatively sufficiently large for the L1 wave of the satellite Sj. j1 For example, 100 for (n) 2The L1 wave of the satellite Sj may be used for the relative positioning process after multiplying the L1 wave by a sufficiently large value such that the influence of the ranging signal on the positioning calculation is reduced.

[0040] The reference station satellite determination unit 81 then calculates the difference ΔI_j2 between the signal strength (dB / Hz) Ir_j2 of the ranging signal in the observation station observation data and the signal strength (dB / Hz) Ib_j2 of the ranging signal in the reference station observation data for the L2 wave (i.e., a carrier wave with a frequency of 1227.60 MHz) transmitted from the satellite Sj, according to the following equation 2 (step S5-5). (Equation 2) ΔI_j2 = Ir_j2-Ib_j2 Here, ΔI_j2: Difference in satellite signal strength for L2 wave of satellite Sj Ir_j2: Signal strength of L2 wave from satellite Sj received by GNSS receiver 1 [dB / Hz] Ib_j2: Signal strength of L2 wave from satellite Sj received by the reference station [dB / Hz] Subscript j2: represents the L2 wave of satellite Sj. The subscript r: represents the GNSS receiver 1 (observation station). Subscript b: denotes reference station.

[0041] The reference station satellite determination unit 81 then determines whether the calculated satellite signal strength difference ΔI_j2 for the L2 wave is equal to or greater than the signal strength difference threshold Tid (step S5-6).

[0042] Then, if the satellite signal strength difference ΔI_j2 for the L2 wave is equal to or greater than the signal strength difference threshold Tid (step S5-6: Yes), the reference station satellite determination unit 81 determines whether the signal strength (dB / Hz) Ib_j2 of the ranging signal of the L2 wave in the reference station observation data is equal to or greater than the elevation angle-corresponding signal strength threshold Tie (step S5-7).

[0043] Then, if the signal strength (dB / Hz) Ib_j2 of the ranging signal of the L2 wave among the reference station observation data is equal to or greater than the elevation angle corresponding signal strength threshold Tie (step S5-7: Yes), and if the satellite signal strength difference ΔI_j2 for the L2 wave is less than the signal strength difference threshold Tid (step S5-6: No), the reference station satellite determination unit 81 classifies the L2 wave of the satellite Sj as a satellite signal wave to be used for the relative positioning process (specifically, for example, the value of the utilization flag of the L2 wave of the satellite Sj is set to 1) (step S5-8). Then, the reference station satellite determination unit 81 advances the relative positioning process procedure to the process of step S5-9.

[0044] On the other hand, if the signal strength (dB / Hz) Ib_j2 of the ranging signal of the L2 wave among the reference station observation data is less than the elevation angle-corresponding signal strength threshold Tie (step S5-7: No), the reference station satellite determination unit 81 does not classify the L2 wave of the satellite Sj as a satellite signal wave to be used for relative positioning processing (specifically, for example, by setting the value of the utilization flag of the L2 wave of the satellite Sj to 0), and proceeds with the relative positioning processing procedure to processing of step S5-9.

[0045] In addition, when the signal strength (dB / Hz) Ib_j2 of the ranging signal of the L2 wave among the reference station observation data is less than the elevation angle corresponding signal strength threshold Tie (step S5-7: No), the observation noise variance value R, which is the diagonal value of the observation noise covariance matrix Rε(n) of the Kalman filter described later, is set to be relatively large enough for the L2 wave of the satellite Sj. j2 For example, 100 for (n) 2 The L2 wave of the satellite Sj may be used for the relative positioning process after multiplying the L2 wave by a sufficiently large value such that the influence of the ranging signal on the positioning calculation is reduced.

[0046] The reference station satellite determination unit 81 then determines whether or not the process has been completed for all of the plurality of satellites Sx from which the reference station has received radio waves (distance measurement signals) (step S5-9).

[0047] Then, if there is a satellite that has not yet been processed among the multiple satellites Sx (step S5-9: No), the reference station satellite determination unit 81 repeats the processes from step S5-1 to step S5-9 for the satellite Sk that has not yet been processed.

[0048] On the other hand, if the processing has been completed for all of the multiple satellites Sx (step S5-9: Yes), the reference station satellite determination unit 81 advances the relative positioning processing procedure to step S6.

[0049] In the above, the processing is performed for each of the L1 wave and the L2 wave transmitted from the satellite Sj, but the processing may be performed for only one of them, and further, the processing may be performed for radio waves (ranging signals) in other frequency bands. Also, when at least one of the L1 wave and the L2 wave transmitted from the satellite Sj is not classified as a satellite signal wave used for relative positioning processing, the satellite Sj that transmitted the L1 wave or the L2 wave may be classified as a satellite not used for relative positioning processing.

[0050] As a result of the processing of step S5 described above, if the signal strength of the radio waves (ranging signals) of the satellite Sj received by the reference station is significantly lower than the signal strength of the radio waves (ranging signals) of the satellite Sj received by the GNSS receiver 1 (step S5-2: Yes, step S5-6: Yes), and if the signal strength expected (in other words, expected) corresponding to the elevation angle of the satellite Sj when the radio wave environment is good is not secured (step S5-3: No, step S5-7: No), the radio waves of the satellite Sj (specifically, in the above case, the ranging signals of the L1 waves and the L2 waves) will not be used for the relative positioning processing.

[0051] The reference satellite selection unit 82 selects a satellite to be positioned as the reference satellite in the relative positioning process (specifically, calculation of double difference) from among the multiple satellites Sx from which the reference station has received radio waves (ranging signals) (step S6).

[0052] In this embodiment, the reference satellite selection unit 82 selects a reference satellite from among multiple satellites for use in calculating the double difference in calculating the relative position based on a satellite evaluation value that is determined by evaluating a combination of the signal strength of the radio waves (ranging signal) received by the reference station and the elevation angle at the GNSS receiver 1 (observation station) for the satellite that transmitted the radio waves (ranging signal).

[0053] The reference satellite selection unit 82 determines a satellite evaluation value for each of the multiple satellites Sx from which the reference station receives radio waves (ranging signals) by comprehensively evaluating the combination of the signal strength of the radio waves and the elevation angle of the satellite at the GNSS receiver 1 (observation station), and selects a reference satellite based on the determined satellite evaluation value.

[0054] The satellite evaluation value is determined so that the stronger the signal strength of the radio wave (ranging signal) at the reference station, the higher the evaluation, and so that the higher the elevation angle of the satellite at the GNSS receiver 1 (observation station), the higher the evaluation. The relationship between the satellite evaluation value and the signal strength and elevation angle is not limited to a specific relationship, and an appropriate relationship is appropriately set, taking into consideration that an optimal reference satellite can be selected.

[0055] The satellite evaluation value may be calculated, for example, according to the following Equation 3. (Equation 3) E = C×Ib_j+Ar_j Here, E: Satellite evaluation value Ib_j: Signal strength of the radio wave from satellite Sj received by the reference station [dB / Hz] Ar_j: Elevation angle [rad] of satellite Sj from which GNSS receiver 1 (observation station) received radio waves C: Coefficient Subscript b: stands for reference station. The subscript r represents GNSS receiver 1 (observation station). The subscript j represents the satellite Sj.

[0056] The coefficient C in the formula 3 is a coefficient for adjusting the difference between the magnitude of the signal strength Ib_j "dB / Hz" of the radio wave and the magnitude of the elevation angle Ar_j [rad] of the satellite, and for setting the weighting of the signal strength with respect to the elevation angle in the overall evaluation of the signal strength of the radio wave and the elevation angle of the satellite when determining the satellite evaluation value E. The coefficient C is not limited to a specific value, and is appropriately set to an appropriate value after considering that the combination of the signal strength and the elevation angle can be appropriately evaluated and the optimum reference satellite can be selected. The coefficient C may be set to any value within a range of about 5 to 15, for example, and particularly to a value of about 10. Here, for the signal strength Ib_j [dB / Hz] of the radio wave in the formula 3, a signal strength that suppresses short-term fluctuating observation noise by applying a low-pass filter with a time constant of about several seconds to several tens of seconds may be used. By applying a low-pass filter to the radio signal strength Ib_j [dB / Hz], the satellite evaluation value E is stabilized, and the reference satellite selected based on the satellite evaluation value E can be prevented from being switched every few seconds due to observation noise.

[0057] The satellite evaluation value may be calculated according to the following equation 4, for example. (Math 4) E = C×Ib_j+Ar_j+G×Qr_j Here, E: Satellite evaluation value Ib_j: Signal strength of the radio wave from satellite Sj received by the reference station [dB / Hz] Ar_j: Elevation angle [rad] of satellite Sj from which GNSS receiver 1 (observation station) received radio waves Qr_j: Status flag of satellite Sj from which GNSS receiver 1 (observation station) received radio waves C: Coefficient G: Coefficient Subscript b: stands for reference station. The subscript r represents GNSS receiver 1 (observation station). The subscript j represents the satellite Sj.

[0058] The coefficient C in Equation 4 is the same as the coefficient C in Equation 3. The coefficient G in Equation 4 is a weighting coefficient for the state flag Qr_j of the satellite Sj, and is a coefficient for adjusting the importance of the half-cycle determination state with respect to the signal strength of the radio wave and the elevation angle of the satellite when determining the satellite evaluation value E, and may be set to a value of about 1000, for example.

[0059] In the formula 4, the status flag Qr_j of the satellite Sj from which the GNSS receiver 1 (observation station) receives radio waves is a state variable that indicates the determined state of a half wavelength (in other words, a half cycle, i.e., 0.5 cycle) of the phase of the ranging signal of the satellite Sj from which the GNSS receiver 1 receives radio waves, and takes a value corresponding to either the determined state of the half cycle or the undetermined state. Specifically, the status flag Qr_j of the satellite Sj is the phase lock state in the PLL (i.e., phase-locked loop) processing in the GNSS receiving unit 3 of the GNSS receiver 1, and if the phase lock of the ranging signal of the satellite Sj is stable, the value becomes 1, which corresponds to the determined state, and if the phase lock of the ranging signal of the satellite Sj is not stable due to the influence of an external factor (e.g., a momentary interruption due to an obstacle), the value becomes 0, which corresponds to the undetermined state.

[0060] In other words, the status flag Qr_j of the satellite Sj is an index showing the stability of the received satellite ranging signal. By multiplying the status flag Qr_j of the satellite Sj by the coefficient G and adding it, the satellite evaluation value E can evaluate a satellite with a stable phase lock of the ranging signal, and a satellite with better quality can be selected as the reference satellite.

[0061] The satellite evaluation value is determined for each of the multiple satellites Sx from which the reference station and GNSS receiver 1 (observation station) receive radio waves (ranging signals), for each L1 wave or L2 wave (or other frequency band radio waves / ranging signals / satellite systems) classified as satellite signal waves to be used for relative positioning processing by the processing in step S5 (specifically, for example, the value of the usage flag is 1).

[0062] The reference satellite selection unit 82 selects, as the reference satellite, the satellite with the highest satellite evaluation value from among the multiple satellites Sx from which the reference station and the GNSS receiver 1 (observation station) have received radio waves (ranging signals).

[0063] For each of the multiple satellites Sx from which the reference station and GNSS receiver 1 (observation station) receive radio waves (ranging signals), a reference satellite is selected based on a satellite evaluation value determined by comprehensively evaluating a combination of the signal strength of the radio waves at the reference station and the elevation angle of the satellite at the observation station, making it possible to select a high-quality satellite as the reference satellite even when the signal strength of some satellites is degraded by obstacles such as trees or radio towers around the reference station. The reference satellite selected based on the satellite evaluation value has good signal strength at the reference station and is not affected by obstacles due to the location or installation method of the reference station, and in addition, a satellite with a high elevation angle at the observation station has small radio wave propagation errors caused by passing through the troposphere or ionosphere above the observation station, making it possible to select a reference satellite of good quality for the radio wave environments of both the reference station and the observation station. In addition, by adjusting the magnitude of coefficient C, which sets the weighting of signal strength relative to the elevation angle in the overall evaluation of radio signal strength and satellite elevation angle when determining the satellite evaluation value E, for example as in Equation 3 or 4, it is also possible to select a reference satellite by placing more importance (in other words, giving priority) on the elevation angle of the observation station than on the signal strength of the reference station.

[0064] The signal strength verification unit 83 verifies (step S7) whether or not the signal strength of the satellite radio waves (ranging signals) received by the reference station is significantly lower than the signal strength of the satellite radio waves (ranging signals) received by the GNSS receiver 1 when a sufficient elevation angle is ensured for each of the multiple satellites Sx from which the reference station has received radio waves (ranging signals) (step S7). Figure 4 is a flow diagram showing the processing procedure in the signal strength verification unit 83, and is a flow diagram showing the details of the processing of step S7 in the flow diagram of Figure 2.

[0065] In this embodiment, the signal strength verification unit 83 multiplies the observation noise of the Kalman filter in calculating the relative position by the difference or a value based on the difference when the difference between the signal strength of the radio wave (ranging signal) received by the GNSS receiver 1 and the signal strength of the radio wave (ranging signal) received by the reference station is greater than or equal to the signal strength difference threshold, and the elevation angle at the reference station for the satellite that transmitted the radio wave (ranging signal) is greater than or equal to the elevation angle threshold.

[0066] The signal strength verification unit 83 performs the process of step S7 below for the L1 waves and L2 waves (or radio waves / ranging signals of other frequency bands) of satellites Sj that are classified as satellite signal waves to be used for relative positioning processing (specifically, for example, the value of the usage flag is 1) for at least one of the L1 waves and L2 waves (or radio waves / ranging signals of other frequency bands) by the process of step S5 among the multiple satellites Sx from which the reference station has received radio waves (ranging signals). That is, the signal strength verification unit 83 skips over the L1 waves and L2 waves (or radio waves / ranging signals of other frequency bands) that are not classified as satellite signal waves to be used for relative positioning processing (specifically, for example, the value of the usage flag is 0) without performing any process.

[0067] The signal strength verification unit 83 first calculates the difference ΔI_j1 between the signal strength (dB / Hz) Ir_j1 of the ranging signal in the observation station observation data and the signal strength (dB / Hz) Ib_j1 of the ranging signal in the reference station observation data for the L1 wave (i.e., the carrier wave with a frequency of 1575.42 MHz) transmitted from the satellite Sj among the multiple satellites Sx, according to the above formula 1 (step S7-1). Note that the difference ΔI_j1 in the satellite signal strength for the L1 wave calculated in the process of the above step S5-1 may be used as it is.

[0068] The signal strength verification unit 83 then determines whether or not the calculated satellite signal strength difference ΔI_j1 for the L1 wave is equal to or greater than the signal strength difference threshold Tid (step S7-2).

[0069] In the process of step S7-2, a value different from the signal strength difference threshold Tid used in the process of step S5-1 described above may be used as the signal strength difference threshold.

[0070] Then, if the difference ΔI_j1 in satellite signal strength for the L1 wave is greater than or equal to the signal strength difference threshold Tid (step S7-2: Yes), the signal strength verification unit 83 determines whether the elevation angle Ab_j of the satellite Sj in the reference station observation data is greater than or equal to the elevation angle threshold Tae (step S7-3).

[0071] The elevation angle threshold Tae is a threshold for detecting a situation where the signal strength of the satellite radio wave (ranging signal) received by the reference station is significantly lower than the signal strength of the satellite radio wave (ranging signal) received by the GNSS receiver 1, in other words, a situation where there is a high possibility that a significantly large observation noise is superimposed on the reference station side, even though a sufficient elevation angle of the satellite is ensured. The elevation angle threshold Tae is not limited to a specific value, and is appropriately set to an appropriate value after considering that the above detection can be performed appropriately and the value of the signal strength difference threshold Tid. For example, when the signal strength difference threshold Tid is about 5 to 15 [dB], the elevation angle threshold Tae is considered to be set to any value in the range of about 50° to 70°, and particularly when the signal strength difference threshold Tid is about 10 [dB], it is considered to be set to a value of about 60°.

[0072] Then, if the elevation angle Ab_j of the satellite Sj in the reference station observation data is greater than or equal to the elevation angle threshold Tae (step S7-3: Yes), the signal strength verification unit 83 outputs the difference ΔI_j1 in the satellite signal strength for the L1 wave to the real solution calculation unit 84 (step S7-4).

[0073] On the other hand, if the satellite signal strength difference ΔI_j1 for the L1 wave is less than the signal strength difference threshold Tid (step S7-2: No), or if the elevation angle Ab_j of the satellite Sj in the reference station observation data is less than the elevation angle threshold Tae (step S7-3: No), the signal strength verification unit 83 calculates the difference ΔI_j2 between the signal strength (dB / Hz) Ir_j2 of the ranging signal in the observation station observation data and the signal strength (dB / Hz) Ib_j2 of the ranging signal in the reference station observation data for the L2 wave (i.e., the carrier wave with a frequency of 1227.60 MHz) transmitted from the satellite Sj according to the above formula 2 (step S7-5). Note that the satellite signal strength difference ΔI_j2 for the L2 wave calculated in the process of the above step S5-5 may be used as it is.

[0074] The signal strength verification unit 83 then determines whether or not the calculated satellite signal strength difference ΔI_j2 for the L2 wave is equal to or greater than the signal strength difference threshold Tid (step S7-6).

[0075] Then, if the satellite signal strength difference ΔI_j2 for the L2 wave is greater than or equal to the signal strength difference threshold Tid (step S7-6: Yes), it is determined whether the elevation angle Ab_j of the satellite Sj in the reference station observation data is greater than or equal to the elevation angle threshold Tae (step S7-7).

[0076] Then, if the elevation angle Ab_j of the satellite Sj in the reference station observation data is greater than or equal to the elevation angle threshold Tae (step S7-7: Yes), the signal strength verification unit 83 outputs the difference ΔI_j2 in the satellite signal strength for the L2 wave to the real solution calculation unit 84 (step S7-8).

[0077] On the other hand, if the satellite signal strength difference ΔI_j2 for the L2 wave is less than the signal strength difference threshold Tid (step S7-6: No), and if the elevation angle Ab_j of the satellite Sj in the reference station observation data is less than the elevation angle threshold Tae (step S7-7: No), the signal strength verification unit 83 determines whether processing has been completed for all of the multiple satellites Sx from which the reference station has received radio waves (ranging signals) (step S7-9).

[0078] If there is a satellite that has not yet been processed among the multiple satellites Sx (step S7-9: No), the signal strength verification unit 83 repeats the processes from step S7-1 to step S7-9 for the satellite Sk that has not yet been processed.

[0079] On the other hand, if the processing has been completed for all of the plurality of satellites Sx (step S7-9: Yes), the signal strength verification unit 83 advances the relative positioning processing procedure to step S8.

[0080] The processing of step S7 above detects a situation in which, even though sufficient height is ensured for the elevation angle Ab_j of satellite Sj (step S7-3: Yes, step S7-7: Yes), the signal strength of the radio waves (ranging signal) from satellite Sj received by the reference station is significantly lower than the signal strength of the radio waves (ranging signal) from satellite Sj received by the GNSS receiver 1 (step S7-2: Yes, step S7-6: Yes), and information that there is a high possibility that significantly large observation noise is superimposed on the reference station side is reflected in subsequent processing.

[0081] The real solution calculation unit 84 calculates real-valued bias (in other words, real solutions of integer-valued bias) by solving a positioning equation based on the observation station observation data and the reference station observation data (step S8).

[0082] In the subsequent processing, observation data on L1 waves and L2 waves (and radio / ranging signals of other frequency bands) classified as satellite signal waves to be used for relative positioning processing by the processing in step S5 (specifically, for example, the value of the usage flag is 1) is used, and the satellite selected by the processing in step S6 is positioned as the reference satellite. Note that since the processing when using L1 waves and the processing when using L2 waves are the same, in the following explanation, no distinction between L1 waves and L2 waves will be mentioned as the processing is common to both L1 waves and L2 waves.

[0083] First, the phase of the ranging signal when the radio wave from the satellite Ss is received at the reference station (in other words, the carrier phase: carrier observation quantity) φb_s [cycle] is expressed by the following Equation 5. (Math. 5) λsφb_s = ρb_s+λsNb_s+c(dtb-dT_s)-Db_s+Tb_s Here, λs: wavelength of the carrier wave of satellite Ss [m] ρb_s: Geometric distance between the reference station and the satellite Ss [m] Nb_s: Real value bias [cycle] dtb: Clock error of the reference station [seconds] dT_s: Satellite clock error [seconds] Db_s: Ionospheric delay between the reference station and the satellite Ss [m] Tb_s: Tropospheric delay between the reference station and the satellite Ss [m] c: Carrier wave speed [m / sec] Subscript b: stands for reference station. The subscript s represents the satellite Ss.

[0084] Regarding the phase of the ranging signal expressed according to Equation 5, when performing relative positioning using observation data from the observation station and observation data from the reference station, the double difference (double phase difference) φrb_uk of the phase of the ranging signal for satellite Su (reference satellite) and satellite Sk at the GNSS receiver 1 (observation station) and the reference station is calculated as shown in Equation 6 below. (Math. 6) λsφrb_uk = ρrb_uk+λsNrb_uk Here, λs: wavelength of the carrier wave of satellite Ss ρrb_uk: double difference of geometric distance Nrb_uk: Double difference of real-valued bias The subscript r: represents the GNSS receiver 1 (observation station). Subscript b: denotes reference station. The subscript u represents the satellite Su (reference satellite). The subscript k represents the satellite Sk.

[0085] As can be seen from Equation 6, by calculating the double difference of the observational quantities, the clock errors of the GNSS receiver 1 (observation station) and the reference station, the clock errors of the satellite, the ionospheric delay, and the tropospheric delay superimposed on the observational data are offset.

[0086] In addition, when performing relative positioning, the double difference φrb_uk of the phase (in other words, the carrier phase) of the ranging signal for satellite Su (reference satellite) and satellite Sk at the GNSS receiver 1 (observation station) and the reference station can be calculated as shown in the following equation 7. (Math. 7) φrb_uk = [φr_u-φb_u]-{φr_k-φb_k} Here, φr_u: Phase of the ranging signal of satellite Su (reference satellite) received by GNSS receiver 1 φb_u: Phase of the ranging signal of the satellite Su (reference satellite) received at the reference station φr_k : Phase of the ranging signal of satellite Sk received by GNSS receiver 1 φb_k: Phase of the ranging signal of satellite Sk received at the reference station The subscript r represents GNSS receiver 1 (observation station). Subscript b: stands for reference station. The subscript u represents the satellite Su (reference satellite). The subscript k represents the satellite Sk.

[0087] The double difference ρrb_uk of the geometric distance in Equation 6 is expressed as ρrb_uk = [ρr_u-ρb_u]-[ρr_k-ρb_k], and the geometric distance ρb_u from the reference station to the satellite Su (reference satellite) and the geometric distance ρb_k from the reference station to the satellite Sk are obtained from the three-dimensional positions of the satellites Su and Sk calculated based on the satellite orbit information (in other words, ephemeris) and the known three-dimensional position of the reference station. Also, the geometric distance ρr_u from the GNSS receiver 1 to the satellite Su (reference satellite) and the geometric distance ρr_k from the GNSS receiver 1 to the satellite Sk are obtained from the three-dimensional positions of the satellites Su and Sk calculated based on the satellite orbit information and the approximate third-order position of the GNSS receiver 1. Since the amount of difference in position from the approximate tertiary position of GNSS receiver 1 to the exact three-dimensional position of GNSS receiver 1 is unknown, it is found as an unknown quantity in the positioning equation, and once the unknown quantity is found, the exact three-dimensional position of GNSS receiver 1 can be found.

[0088] In addition, the double difference Nrb_uk of the real-valued bias in equation 5 is expressed as Nrb_uk = [Nr_u-Nb_u]-[Nr_k-Nb_k] using the real-valued bias Nr_u between GNSS receiver 1 and satellite Su, the real-valued bias Nb_u between the reference station and satellite Su, the real-valued bias Nr_k between GNSS receiver 1 and satellite Sk, and the real-valued bias Nb_k between the reference station and satellite Sk.

[0089] If a satellite with poor quality ranging signal is selected as the reference satellite, the error will be superimposed on all observation amounts calculated by double difference calculation. In contrast, the above-mentioned process in step S6 selects the reference satellite (satellite Su in formula 5) based on a satellite evaluation value determined by comprehensively evaluating a combination of the signal strength of the radio wave and the elevation angle of the satellite from among the multiple satellites Sx from which the reference station has received radio waves (ranging signals). Therefore, a satellite with high quality ranging signal is selected as the reference satellite, and good observation amounts can be obtained as a result of the double difference calculation.

[0090] A positioning equation in which the double difference φrb_uk obtained according to Equation 7 is used as an observation quantity is expressed as Equation 8 below. (Equation 8) y = H x + ε

[0091] In Equation 8, y is an observation vector having as its element the double difference φrb_uk obtained according to Equation 7, H is a design matrix, and further, x is an unknown vector having as its elements the three-dimensional position (unknown) of the GNSS receiver 1 and the double difference Nrb_uk (unknown) of the real-valued bias in Equation 6. Also, ε is an observation noise term.

[0092] The real solution calculation unit 84 obtains the unknown vector x of Equation 8 (specifically, having as elements the three-dimensional position of the GNSS receiver 1 and the double difference Nrb_uk of the real-valued bias) by applying a Kalman filter (see Equation 9 below).

[0093]

number

[0094] The variables in Equation 9 are as follows (note that "x^" in the following indicates that there is a ^ directly above the x): n: time x^(n|n-1): Estimated at time n using information up to time (n-1). Prior estimated state quantity x^(n|n) : Estimated at time n using information up to time n Posterior estimated state quantity y(n): Observed value F(n): State transition matrix M(n): Observation matrix K(n): Kalman gain P(n|n-1): prior error covariance matrix P(n|n): Posterior error covariance matrix Rε(n): Observation noise covariance matrix Rδ(n): system noise covariance matrix I: identity matrix T: stands for transposition.

[0095] Regarding the relationship between Formula 8 and Formula 9, the observation value y(n) in Formula 9 corresponds to the observation vector y in Formula 8, and the observation matrix M(n) corresponds to the design matrix H in Formula 8.

[0096] According to Equation 9, the posterior estimated state quantity x^(n|n) is calculated by multiplying the observation prediction error by the Kalman gain K(n) and adding the result to the a priori estimated state quantity x^(n|n-1). Specifically, a real-valued bias (in other words, a real solution of the integer-valued bias) is calculated. The three-dimensional position of the GNSS receiver 1 calculated using the real-valued bias (in other words, a real solution of the integer-valued bias) is called a "float solution."

[0097] Here, when the difference ΔI_j1 in the satellite signal strength for the L1 wave or the difference ΔI_j2 in the satellite signal strength for the L2 wave is output in the process of step S7, the real solution calculation unit 84 calculates the observation noise variance value R j1 (n), R j2 A calculation is performed by applying a Kalman filter using the observation noise covariance matrix Rε(n) calculated by multiplying (n) by the satellite signal strength differences ΔI_j1, ΔI_j2. Note that if the satellite signal strength difference ΔI_j1 for the L1 wave is not output in the processing of step S7, ΔI_j1=1 is set, and if the satellite signal strength difference ΔI_j2 for the L2 wave is not output, ΔI_j2=1 is set.

number

[0098] Each variable (scalar value) in Equation 10 is as follows: R u1 (n): Observation noise variance of the L1 ranging signal from satellite Su (reference satellite) R u2 (n): Observation noise variance of the L2 ranging signal from satellite Su (reference satellite) R j1 (n): Observation noise variance of the L1 wave ranging signal of satellite Sj (other than the reference satellite) R j2 (n): Observation noise variance of the L2 wave ranging signal of satellite Sj (other than the reference satellite) ΔI_j1: Difference in satellite signal strength with respect to the L1 ranging signal of satellite Sj (other than the reference satellite) ΔI_j2: Difference in satellite signal strength with respect to the L2 ranging signal of satellite Sj (other than the reference satellite) where j=1,2,3,...,m

[0099] Here, in the above formula 10, the observation noise variance value R of the satellite Sj other than the reference satellite j1 (n), R j2 (n) is multiplied by the satellite signal strength differences ΔI_j1, ΔI_j2. However, the process of multiplying by the satellite signal strength differences ΔI_j1, ΔI_j2 is not limited to the process for satellites other than the reference satellite. For example, the observation noise variance value R u1 (n) is multiplied by a value based on the satellite signal strength difference ΔI_j1 (where j = 1, 2, 3, . . . , m) (specifically, for example, the average value of the satellite signal strength difference ΔI_j1), or the observation noise variance value R u2 (n) may be multiplied by a value based on the satellite signal strength difference ΔI_j2 (where j=1, 2, 3, . . . , m) (specifically, for example, the average value of the satellite signal strength differences ΔI_j2).

[0100] In addition, in the above formula 10, only the diagonal elements of the observation noise covariance matrix Rε(n) are multiplied by the satellite signal strength differences ΔI_j1, ΔI_j2, but the elements to be multiplied by the satellite signal strength differences ΔI_j1, ΔI_j2 are not limited to the diagonal elements, and elements other than the diagonal elements may also be multiplied by the satellite signal strength differences ΔI_j1, ΔI_j2.

[0101] Furthermore, in the above formula 10, the observation noise covariance matrix Rε(n) is multiplied directly by the satellite signal strength differences ΔI_j1, ΔI_j2, but the value by which the observation noise covariance matrix Rε(n) is multiplied is not limited to the satellite signal strength differences ΔI_j1, ΔI_j2 themselves, and may be, for example, a value that changes depending on the magnitude of the satellite signal strength differences ΔI_j1, ΔI_j2 (in other words, a value based on the satellite signal strength differences ΔI_j1, ΔI_j2), and specifically, for example, it may be a value calculated by a function that uses the satellite signal strength differences ΔI_j1, ΔI_j2 as variables, or a value that is determined in advance for each range of the satellite signal strength differences ΔI_j1, ΔI_j2.

[0102] The integer solution calculation unit 85 converts the real-valued bias calculated by the process of step S8 into an integer (in other words, finds an integer solution of the integer-valued bias based on the real-valued solution of the integer-valued bias) (step S9).

[0103] The integer solution calculation unit 85, for example, finds an integer bias (integer solution; i.e., wave number) with the smallest error for the real value bias (real solution) calculated by the processing of step S8 as a first candidate, and finds an integer bias (integer solution; i.e., wave number) with the next smallest error as a second candidate. Although the method of identifying an integer solution with a small error is not limited to a specific method, for example, the integer least squares method is used, and in particular, the LAMBDA method, which identifies a solution by narrowing the search space of integer solutions by uncorrelating the integer bias, may be used.

[0104] The integer solution calculation unit 85 then judges whether or not to fix the integer solution specified above. Specifically, it judges the reliability of the integer solution specified above, and if it is judged that a reliable integer solution has been obtained, it corrects and calculates the position found by the real solution calculation unit 84 using the integer bias of the first candidate. The three-dimensional position of the GNSS receiver 1 calculated using the integer bias (in other words, the integer solution of the integer bias, i.e., the wave number) is called a "fix solution."

[0105] The method for determining the reliability of the integer solution is not limited to a specific method, but may be, for example, a ratio test. The ratio, which is an index used in the ratio test, is the ratio of the distance between the real value bias and the second candidate of the integer value bias to the distance (called the "norm") between the real value bias (in other words, the real solution of the integer value bias) and the first candidate of the integer value bias (in other words, the integer solution of the integer value bias). Generally, the higher the ratio is, the higher the reliability of the first candidate of the integer value bias is. Therefore, it is conceivable to set an appropriate threshold value, and when the ratio is greater than the threshold value, determine that the reliability of the integer value bias is high, and adopt the first candidate of the integer value bias.

[0106] According to the positioning device 8 described above, if the signal strength of the radio waves (ranging signals) received by the reference station is significantly lower than the signal strength of the radio waves (ranging signals) received by the GNSS receiver 1, and if the signal strength expected (in other words, anticipated) in accordance with the elevation angle of the satellite when the radio wave environment is good is not secured, the radio waves (ranging signals) of the satellite in question are not used for processing the relative positioning (step S5). Therefore, even if the observation information transmitted from the reference station becomes of low quality, it is possible to perform relative positioning on the GNSS receiver 1 side with little deterioration in the positioning accuracy of the relative positioning.

[0107] According to the positioning device 8 as described above, a reference satellite is selected from among multiple satellites from which the reference station receives radio waves (ranging signals) based on a satellite evaluation value determined by comprehensively evaluating a combination of the signal strength of the radio waves (ranging signals) and the elevation angle of the satellite at the GNSS receiver 1 (in other words, the observation station). Therefore, a high-quality satellite taking into account the radio wave environments of both the reference station and the ranging signals at the GNSS receiver 1 (observation station) is selected as the reference satellite (step S6). As a result of the double difference calculation based on the reference satellite, good observation amounts can be obtained. Even if the signal strength of the satellite received by the reference station decreases and the observation information transmitted from the reference station becomes of low quality, it is possible to perform relative positioning on the GNSS receiver 1 side with less deterioration in the positioning accuracy of the relative positioning.

[0108] According to the positioning device 8 as described above, in a case where the signal strength of the radio waves (ranging signals) received by the reference station is significantly lower than the signal strength of the radio waves (ranging signals) received by the receiver, that is, when significantly large observation noise is superimposed on the reference station side despite the elevation angle of the satellite being sufficiently high, the observation noise of the Kalman filter is multiplied by the signal strength difference or a value based on the signal strength difference (steps S7 and S8). Therefore, the observation noise can be appropriately incorporated in the processing of relative positioning, and even if the observation information transmitted from the reference station becomes of low quality, it becomes possible to perform relative positioning on the GNSS receiver 1 side with less deterioration in the position accuracy of the relative positioning.

[0109] Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there are design changes and the like within the scope of the gist of the present invention, they are included in the present invention.

[0110] For example, in the above embodiment, in the processing of step S5, it is determined whether the difference in satellite signal strength is equal to or greater than the signal strength difference threshold, and it is also determined whether the signal strength of the ranging signal of the reference station is equal to or greater than the elevation angle-corresponding signal strength threshold, and it is determined whether or not to use the ranging signal of each of the multiple satellites for the relative positioning processing. However, the processing of step S5 is not an essential configuration for this invention, and, for example, all of the received ranging signals may be used for the relative positioning processing, or it may be determined whether or not to use the ranging signal of each of the multiple satellites for the relative positioning processing based only on the signal strength of the ranging signal.

[0111] In the above embodiment, in the process of step S7, it is determined whether the difference in satellite signal strength is equal to or greater than the signal strength difference threshold, and it is also determined whether the elevation angle of the satellite is equal to or greater than the elevation angle threshold, so that it is determined whether extremely large observation noise is superimposed on the reference station side, but the process of step S7 is not an essential configuration for this invention, and it is also possible not to determine whether extremely large observation noise is superimposed on the reference station side. Therefore, it is also possible not to adjust the observation noise taken into account in the calculation of the integer bias (and other processes).

[0112] Furthermore, the key point of this invention is that a reference satellite is selected based on a satellite evaluation value that is determined by evaluating a combination of the signal strength of the ranging signal received by the reference station and the elevation angle at the reference station of the satellite that transmitted the ranging signal (step S6). The specific configurations of the GNSS receiver 1 and the positioning device 8 are not limited to the example shown in Figure 1, and the processing contents other than the key points are not limited to the processing contents in the above embodiment. [Industrial Applicability]

[0113] The present invention can be applied to, for example, the fields of in-vehicle navigation systems, vehicle control, and automatic driving systems. In addition, the present invention can be applied not only to relative positioning methods using carrier phase (in other words, carrier observables), but also to relative positioning methods using pseudo-range (in other words, code observables). [Explanation of symbols]

[0114] 1 GNSS receiver 2 GNSS antennas 3 GNSS receiver 4 Data communication antenna 5 Data receiving section 6 Satellite information acquisition section 7 Reference station information acquisition section 8 Positioning Device 81 Reference station satellite judgment section 82 Reference satellite selection section 83 Signal Strength Verification Unit 84 Real Solution Calculation Section 85 Integer solution calculation part

Claims

[Claim 1] A positioning device in which a reference station and a receiver receive ranging signals transmitted from a plurality of satellites and calculate a relative position of the receiver with respect to the reference station, selecting a reference satellite from among the plurality of satellites when calculating a double difference of observation data in the calculation of the relative position based on an evaluation value determined by evaluating a combination of a signal strength of the ranging signal received by the reference station, an elevation angle in the receiver with respect to the satellite that transmitted the ranging signal, and a state variable that indicates a definite state of a half wavelength of the phase of the ranging signal of the satellite whose radio wave is received by the receiver; the evaluation value is calculated according to E=C×Ib_j+Ar_j+G×Qr_j (where E: satellite evaluation value, Ib_j: signal strength [dB / Hz] of the ranging signal of the satellite Sj received by the reference station, Ar_j: elevation angle [rad] at the receiver for the satellite Sj that transmitted the ranging signal, Qr_j: status flag indicating a determined state of a half wavelength of the phase of the ranging signal of the satellite Sj received by the receiver, which is a value of 1 corresponding to a determined state or a value of 0 corresponding to an undetermined state, C: coefficient, G: coefficient, and subscript j: satellite Sj). A positioning device characterized by:

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