Relative position detection system, relative position detection method, and phase detection device

Abstract

To provide a relative position detection system and a relative position detection method that allow high-accuracy positioning with an error of several cm by using radio waves from a GNSS satellite, and to provide a phase detection device that achieves carrier phase detection with low power consumption.SOLUTION: A relative position detection system and a relative position detection method of the present invention detect an instantaneous value of a carrier wave phase at the time precisely matching a predetermined UTC time, and determine an evaluation index for all the possible combinations of satellite pairs by using the instantaneous value to achieve high-accuracy positioning. A phase detection device of the present invention corrects the sampling time of the carrier wave phase to obtain an instantaneous value of the carrier wave phase to achieve sampling of the carrier wave phase matching the UTC time despite its low power consumption.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD

[0001] The present invention relates to a relative position detection system, a relative position detection method, and a phase detection device. BACKGROUND ART

[0002] In dangerous areas where disasters such as landslides are likely to occur, ground monitoring systems using GPS (Global Positioning System) or GNSS (Global Navigation Satellite System) have been proposed to monitor slight displacements of the ground and structures. Here, GPS is a term representing an artificial satellite system operated by the United States, and GNSS is a term representing artificial satellite systems launched by countries including the United States, such as Japan, Europe, and China. Although the present invention will be described uniformly with respect to GNSS, it goes without saying that the present invention is applicable to GPS.

[0003] GNSS position detection methods can be broadly divided into two types: a method of detecting code information and a method of detecting carrier phase. The method of detecting code information is widely and generally used in applications such as car navigation. Since the code information transmitted from GNSS satellites changes at about 1 MHz, the position on the earth (latitude, longitude, and altitude) can be known with an accuracy of several meters to about ten meters.

[0004] Not only the position but also accurate time (GPS time) can be detected from the code information. For example, commercially available GNSS receivers often provide a pulse (1PPS) synchronized with GPS time. 1PPS is a time pulse that matches GPS time with a high accuracy of about 10 nanoseconds error regardless of where the GNSS receiver is located on the earth.

[0005] By applying a leap second correction to GPS time, it can be converted to UTC (Coordinated Universal Time), which is common worldwide. Adding 9 hours to UTC converts it to Japan Standard Time (JST). In the following explanation, we will assume that the GNSS receiver detects UTC, but you may substitute UTC with GPS time or JST.

[0006] When higher positional accuracy than that provided by code information is required, a method that detects the carrier phase is used. It is known that by using a high-frequency carrier (approximately 1.5 GHz), positioning can be achieved with an accuracy of less than a few centimeters. Methods for detecting the carrier phase include those called RTK (Real-Time-Kinematic) or carrier phase relative positioning, and devices equipped with RTK are commercially available.

[0007] For example, Patent Document 1 discloses a carrier phase relative positioning device that installs multiple antennas on a moving object and at a fixed position, receives radio waves from multiple GNSS satellites, calculates the double phase difference, determines an integer bias N, and then estimates the vector (relative position vector) between the moving object and the fixed position.

[0008] As described in Patent Document 1, the conventional carrier phase positioning method (hereinafter referred to as the conventional method) is a positioning method that determines the dual phase difference by designating one reference satellite (hereinafter referred to as the reference satellite). This conventional method has the following three problems (1) to (3): (1) Because the integrated value of the carrier phase detected from the radio waves of each satellite (integrated phase) is required, the amount of information is large and positioning calculations are difficult. (2) If the radio waves from the reference satellite are lost, the integer bias N must be recalculated, which may cause the positioning to be interrupted. (3) If noise is mixed into the carrier phase detected from the reference satellite, the positioning error will increase.

[0009] Therefore, Patent Document 2 discloses a device that acquires the carrier phase as an instantaneous value at a predetermined sampling timing synchronized with UTC and performs positioning. The device disclosed in Patent Document 2 can solve the problems of (1) and (2) described above.

[0010] However, even with the apparatus described in Patent Document 2, problem (3) cannot be solved. Furthermore, the apparatus described in Patent Document 2 requires sampling the carrier phase to precisely match UTC, which necessitates a high operating frequency for the GNSS receiver, creating a new problem of high power consumption. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Patent No. 3532267 specification [Patent Document 2] Japanese Patent Publication No. 2022-112022 [Overview of the project] [Problems that the invention aims to solve]

[0012] Therefore, the present invention aims to provide a relative position detection system and a relative position detection method that use carrier phase to achieve highly accurate and stable positioning even when radio waves from some satellites are interrupted or when the noise level of the carrier phase is high. Furthermore, the present invention aims to provide a phase detection device that can realize such a relative position detection system and relative position detection method with low power consumption. [Means for solving the problem]

[0013] [1] The relative position detection system of the present invention comprises a plurality of antennas (2A, 2B), a phase detection device (3A, 3B) connected to each of the plurality of antennas (2A, 2B) that receives radio waves from a plurality of GNSS satellites (Sat1, Sat2, Sat3, Sat4) and detects instantaneous values ​​of carrier phase (φA(1), φA(2), φA(3), φA(4)) and (φB(1), φB(2), φB(3), φB(4)), and a positioning means (4) that measures the relative position vector P' between the plurality of antennas (3A and 3B) using the instantaneous values ​​of carrier phase, wherein the positioning means (4) measures the difference in instantaneous values ​​of carrier phase with respect to a satellite pair (n,r) consisting of two satellites extracted from the plurality of GNSS satellites The relative position detection system (1) is characterized by including a double phase difference calculation means (44) that calculates a double phase difference θ(n,r) by performing calculations; a satellite position information acquisition means (43) that acquires the satellite position of the GNSS satellite; an evaluation means (42) that uses the double phase difference θ(n,r) and the satellite position to determine an evaluation index E(n,r,P') of the relative position vector P'; and an overall evaluation means (41) that integrates the evaluation index E(n,r,P') for different satellite pairs (n,r) to calculate an overall evaluation index Energy(P').

[0014] [2] In the relative position detection system of the present invention, the evaluation means (42) preferably includes a lattice vector calculation means for determining a lattice vector k(n,r) related to the satellite pair (n,r), a theoretical double difference calculation means for determining a theoretical double phase difference Φ(n,r,P') by calculating the dot product of the lattice vector k(n,r) and the relative position vector P', and a phase difference evaluation means (426) for evaluating the difference between the theoretical double phase difference Φ(n,r,P') and the double phase difference θ(n,r) and outputting the evaluation index E(n,r,P').

[0015] [3] In the relative position detection system of the present invention, the overall evaluation by the overall evaluation means (41) preferably uses an evaluation index E(n,r,P') for all possible combinations of satellite pairs (n,r).

[0016] [4] In the relative position detection system of the present invention, it is preferable that the instantaneous value of the carrier phase has a change range within 2π radians.

[0017] [5] The relative position detection method of the present invention is a relative position detection method that uses a plurality of phase detection devices connected to a plurality of antennas to receive radio waves from a plurality of GNSS satellites and detect instantaneous values ​​of carrier phase, and measures a relative position vector between antennas using the instantaneous values ​​of carrier phase, wherein the positioning is characterized by determining a dual phase difference using the instantaneous values ​​of carrier phase for a satellite pair (n,r), obtaining the satellite positions of the plurality of GNSS satellites, determining an evaluation index for the relative position vector P' using the dual phase difference θ(n,r) and the satellite positions, and comprehensively evaluating the evaluation index for the plurality of satellite pairs to obtain the relative position vector as the positioning result.

[0018] [6] The phase detection device (3) of the present invention includes a satellite signal receiving unit (31) that receives radio waves transmitted from multiple GNSS satellites and detects the carrier phase θ(n), carrier offset frequency Dp(n), code information, and pseudo-distance Pr(n) of multiple GNSS satellites (n) at the device time (Tr), A time error acquisition unit (32) that uses the code information and the pseudo-distance Pr(n) to determine the error (Δ(n)) of the device time, An instantaneous phase calculation unit (33) calculates the instantaneous value φ(n) of the carrier phase at a predetermined time (Ts) by correcting the carrier phase θ(n) using the carrier offset frequency Dp(n) and the device time error (Δ(n)) obtained from the plurality of satellite signal receiving units, A phase detection device (3) is characterized by including a data transmission unit (35) that transmits the instantaneous value φ(n) of the carrier phase.

[0019] [7] In the phase detection device (3) of the present invention, it is preferable that the instantaneous phase calculation unit (33) limits the instantaneous value φ(n) of the carrier phase to the range of 0 to 2π radians.

[0020] [8]In the phase detection device (3) of the present invention, it is preferable that the data transmission unit (35) transmits position information (latitude, longitude, altitude) detected from the code information in addition to the instantaneous value φ(n) of the carrier phase. Effects of the Invention

[0021] The relative position detection system and relative position detection method of the present invention obtain an evaluation index for each satellite pair using the carrier phase acquired from the phase detection device, and integrate the evaluation indices obtained from many satellite pairs to detect the relative position. Therefore, the present invention can provide a relative position detection system and a relative position detection method that can achieve high-precision and stable positioning even when radio waves from some satellites are interrupted or when the noise level of the carrier phase is high.

[0022] The phase detection device of the present invention comprises a satellite signal receiving unit that detects the carrier phases, carrier offset frequencies, code information and pseudoranges of a plurality of GNSS satellites at the device time, and corrects the carrier phases using the carrier offset frequencies, code information and pseudoranges obtained from the plurality of satellite signal receiving units to calculate an instantaneous value of the carrier phase at a predetermined time. As a result, the operating frequency of the satellite signal receiving unit can be kept low, and a phase detection device with lower power consumption than conventional devices can be realized.

[0023] When performing positioning calculation using the phase detection device of the present invention, the amount of information transmitted to the positioning calculation unit can be small. Therefore, in the present invention, a long-distance wireless transmission system such as LPWA (Low Power Wide Area) can be applied as an information transmission means from the phase detection device. In this case, by installing the phase detection device of the present invention in mountains where mobile phones have no signal, it becomes possible to detect landslides in the mountains. Brief Description of the Drawings

[0024] [Figure 1] It is an explanatory diagram illustrating the concept of high-precision positioning using carrier phase according to a conventional method. [Figure 2] Fig. 1 is a configuration example of the relative position detection system 1A of the present invention. [Figure 3] This is a flowchart showing the positioning calculation of the positioning means 4A of the present invention. [Figure 4] This is a flowchart of the calculation (step S6) for determining the evaluation index using the evaluation means 42 of the present invention. [Figure 5] This is an example of the configuration of the evaluation means 42 used in the relative position detection system 1A. [Figure 6] This is an example of the configuration of the phase detection device 3 of the present invention. [Figure 7] This is an example of the configuration of the instantaneous phase calculation unit 33 that constitutes the phase detection device 3. [Figure 8] This diagram schematically represents the internal signal waveform of the instantaneous phase calculation unit 33. [Figure 9] This is an example of the payload format transmitted by the phase detection device 3 of the present invention. [Figure 10] This is a simulation result confirming the relative position detection method of the present invention through simulation. [Figure 11] This is a simulation result confirming the relative position detection method of the present invention through simulation. [Figure 12] These are the experimental results confirming the relative position detection method of the present invention. [Figure 13] This is an example of the configuration of the relative position detection system 1B in Embodiment 2. [Figure 14] This is an example of the configuration of the phase detection device 3 in Embodiment 3. [Figure 15] This is an example of the payload format transmitted by the phase detection device 3 in Embodiment 4. [Modes for carrying out the invention]

[0025] <Overview of the Relative Position Detection Method of the Present Invention> The outline of the present invention will be explained in comparison with conventional methods. Hereafter, satellite numbers will be enclosed in parentheses. For example, "satellite number n" will be represented as "(n)" and "reference satellite r" will be represented as "(r)". Also, for each of the two antennas and phase detection devices, one will be referred to as A and the other as B. For example, the instantaneous value of the carrier phase of GNSS satellite Sat1 detected by phase detection device 2A will be denoted as φA(1). Furthermore, the explanation will be given as an example of receiving signals from four GNSS satellites (Sat1 to Sat4), but it is also possible to receive radio waves from more GNSS satellites.Hereafter, the number of GNSS satellites received will be referred to as M.

[0026] [Conventional method] Figure 1 illustrates a high-precision positioning detection method using carrier phase as exemplified in Patent Document 1. Radio waves from four GNSS satellites (Sat1 to SAt4) in the sky are received by two antennas (2A and 2B) and converted into electrical signals. Antenna 2A is installed at a reference position. Phase detection devices (3A and 3B) are connected to each of the two antennas, and GNSS reception is performed by the phase detection devices to detect the carrier phases (ΩA(1), ΩA(2), ΩA(3), ΩA(4)) and (ΩB(1), ΩB(2), ΩB(3), ΩB(4)) of each satellite. Positioning means 4 uses these carrier phases to determine the relative position to antenna 2B, which is placed at an unknown location, and outputs a relative position vector P'. Hereafter, the distance R between the two antennas may be referred to as the "baseline length".

[0027] The positioning means 4 consists of an RTK calculation unit 49 that performs positioning calculations, a dual phase difference calculation means 44, and a communication means 46.

[0028] The dual phase difference calculation means 44 outputs a dual phase difference θ(n,r) from the carrier wave phase obtained from the reference satellite (r) and other satellites (n). This calculation removes various disturbances, such as changes in propagation delay in the ionosphere. When the reference satellite (r = 1) is set, three sets of dual phase differences (θ(2,1), θ(3,1), θ(4,1)) are obtained. The RTK calculation unit 49 performs positioning using these three sets of dual phase differences.

[0029] If RA(n) and RB(n) are the distances from satellite (n) to antennas 2A and 2B, N(n) is the integer bias, and λ is the carrier wavelength (approximately 19 cm), then the three sets of double phase differences are expressed by equation 1 below.

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[0030] In the conventional method, it is necessary to use the same reference satellite (i.e., to make the underlined terms in Equation 1 the same). Therefore, when radio waves are received from M satellites, the system of equations in Equation 1 becomes M-1. The number of unknowns exceeds the number of equations, and in this state, Equation 1 cannot be solved.

[0031] Therefore, conventional methods acquire carrier phases at different times and perform positioning calculations by preparing multiple sets of simultaneous equations as shown in Equation 1. Because carrier phases acquired at different times are used, an "integrated phase" obtained by integrating the carrier phases over time is used. This integrated phase has the disadvantage of containing a large amount of information and requiring high-speed communication.

[0032] Furthermore, the conventional method had the problem that, because it calculated an integer bias for a single reference satellite, the positioning results would fluctuate significantly if the reference satellite's signal was strongly affected by noise. In addition, the conventional method had the problem that if the reference satellite could not be received, the integer bias had to be recalculated, causing the positioning to be interrupted.

[0033] Next, Embodiment 1 of the present invention will be described.

[0034] [Embodiment 1] Figure 2 shows an example of the configuration of the relative position detection system 1A of the present invention. As in the conventional example, radio waves from four satellites (Sat1 to Sat4) are converted into electrical signals by two antennas (2A and 2B), the carrier wave phase is detected by a phase detection device (3A and 3B), and the positioning means 4 outputs the relative position vector P' between the antennas (2A and 2B).

[0035] In this invention, the positioning means 4 consists of a comprehensive evaluation means 41, an evaluation means 42, a satellite position information acquisition means 43, a dual phase difference calculation means 44, a system controller 45, and a communication means 46. The operation of each means will be described later with reference to Figures 3 and 4.

[0036] The two phase detection devices 3A and 3B each sample the carrier phase at a timing synchronized with UTC and output instantaneous values ​​of the carrier phase φA(n) and φB(n). (Hereafter, these instantaneous values ​​of the carrier phase synchronized with UTC will be referred to as "instantaneous phase.") Phase detection devices 3A and 3B each transmit the instantaneous phase to the positioning means 4 via the communication means 46. In most cases, the communication means 46 is implemented by a wireless communication device, but a wired communication device such as a coaxial cable can also be used.

[0037] The dual phase difference calculation means 44 calculates the dual phase difference θ(n,r) from the instantaneous phases φA(n) and φB(n), the satellite position information acquisition means 43 obtains the satellite position, and the evaluation means 42 uses this information (dual phase difference, satellite position, and estimated relative position vector P' described later) to calculate an evaluation index. The overall evaluation means 41 adds the evaluation index obtained for the positioning pair (n,r) to the overall evaluation index. The estimated relative position vector P' that minimizes the overall evaluation index is searched for and output as the positioning result.

[0038] Figure 3 is a flowchart of the positioning calculation controlled by the system controller 45. The details of the positioning calculation will be explained below in accordance with Figure 3.

[0039] [Step S0] In step S0, the system controller 45 obtains instantaneous carrier phase values ​​φA(n) and φB(n) from the communication means 46.

[0040] [Step S1] In step S1, the system controller 45 sets the central position vector P0 for the search. When used for disaster detection such as landslides, the installation positions of antennas 2A and 2B are approximately known. Therefore, the central position vector P0 can be determined by subtracting the position coordinates of the two antennas. Positioning in this embodiment is performed by searching in three dimensions with this central position vector P0 as the center.

[0041] [Step S2] Next, in step S2, the system controller 45 adds an offset vector to the center position vector P0 to tentatively determine the estimated relative position vector P'.

[0042] In the following explanation, the estimated relative position vector P' will be expressed in polar coordinates (R, α, β). That is, R is the distance between antennas, α is the azimuth angle with respect to the north-south line, and β is the elevation angle in the vertical direction.

[0043] The estimated relative position vector P' is the sum of the center position vector (R0, α0, β0) and the offset vector (ΔR, Δα, Δβ), as shown in equation 2 below.

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[0044] [Step S3] In step S3, the system controller 45 sequentially extracts all possible combinations of satellite pairs. For example, if four GNSS satellites (Sat1 to Sat4) are received, there are six possible satellite pairs as shown in equation 2 below. In step S3, these six satellite pairs are sequentially extracted.

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[0045] As shown in Equation 1, the conventional method uses only three combinations: (2,1), (3,1), and (4,1). Therefore, in the conventional method, the carrier phase obtained from the reference satellite (r=1) is evaluated using three equations, while the carrier phases obtained from satellites 2, 3, and 4 are used only once. In contrast, this method uses all six combinations, enabling high-precision positioning by evaluating the information obtained from all satellites equally.

[0046] [Step S4] Next, in step S4, the dual phase difference calculation means 44 performs the difference calculation of Equation 4 on the satellite pair (n,r) to obtain the dual phase difference θ(n,r).

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[0047] [Step S5] Next, in step S5, the satellite position information acquisition means 43 obtains the position (X(n), Y(n), Z(n)) of each satellite. Specifically, the satellite position (X(n), Y(n), Z(n)) is determined by solving Kepler's equations using satellite orbit information (ephemeris) Ep. Here, since satellite orbit information Ep is broadcast as code information from each satellite, it can be obtained by installing a commercially available GNSS receiver and receiving satellite radio waves. Alternatively, satellite orbit information Ep can be downloaded from an internet server published by the Geospatial Information Authority of Japan, etc.

[0048] [Step S6] In step S6, the evaluation means 42 uses the three types of information described above (double phase difference, satellite position, and estimated relative position vector P') to perform the evaluation index calculation shown in Figure 5 and obtain the evaluation index E(n,r,P'). The evaluation index is an index that represents the correctness of the estimated relative position vector P'. In an ideal state without noise, when the estimated relative position vector P' is the correct value, the evaluation index becomes "0".

[0049] [Step S7] In step S7, the comprehensive evaluation means 41 adds the evaluation index E(n,r,P') described above to the comprehensive evaluation index Ex(P').

[0050] [Step S8] In step S8, the system controller 45 determines whether the calculations in steps S3 to S7 have been performed for all possible positioning pairs (n,r). If there are any remaining pairs, the process returns to step S3, and the evaluation index calculation is performed for the new positioning pairs. Once it is determined that the processing for all positioning pairs (n,r) is complete, the process proceeds to step S9. At this point, the overall evaluation index Ex(P') represented by equation 5 below is obtained.

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[0051] [Step S9] In step S9, the system controller 45 determines whether or not it has calculated the overall evaluation index Ex(P') for all possible estimated relative position vectors P'. If there are any P' for which the overall evaluation index has not been calculated, the process returns to step S2, where a new offset vector (ΔR, Δα, Δβ) is added to the center position vector P0 to update the estimated relative position vectors P', and the process of calculating the overall evaluation index restarts. When the overall evaluation index Ex(P') has been calculated for all estimated relative position vectors P', the process proceeds to step S10.

[0052] [Step S20] In step S10, the system controller 45 outputs the estimated relative position vector P' with the smallest overall evaluation index Ex(P') as the positioning result, and the positioning calculation is completed.

[0053] [Calculation of evaluation metrics] The evaluation index calculation performed by the evaluation means 42 to determine the evaluation index E(n,r,P') is carried out in steps S61 to S65 of Figure 4. These steps will be explained sequentially from here on. [Step S61] First, in step S61, the coordinates (Xa, Ya, Za) of the reference position where antenna 2A is placed are obtained by converting the latitude and longitude of the reference position into a geocentric Cartesian coordinate system.

[0054] [Step S62] In step S61, the direction vector v(n) from the reference position (Xa, Ya, Za) to the coordinates (X(n), Y(n), Z(n)) of satellite (n) is calculated using equation 6 below. The direction vector v(r) for the reference satellite (r) is calculated in the same manner.

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[0055] Here, the magnitude of the direction vector v(n) is normalized by the distance r(n) obtained in equation 7 below.

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[0056] [Step S63] In step S63, the grid vector k(n,r) is obtained by subtracting the direction vector v(r) to the reference satellite (r) from the direction vector v(n) to satellite (n), as shown in equation 8 below.

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[0057] [Step S64] In step S64, the theoretical double phase difference Φ(n,r,P') is obtained by performing an inner product operation between the lattice vector and the estimated relative position vector P' using the following equation 10.

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[0058] [Step S65] The theoretical double phase difference obtained through the above process and the measured double phase difference are both phase information. Therefore, in step S65, the difference between the two phase information is evaluated as shown in equation 11 below. That is, the difference is calculated as two phasors and the evaluation index E(n,r,P') is obtained.

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[0059] The evaluation index E(n,r,P') in the above equation should take its minimum value when the distance between the relative position vector P and the estimated relative position vector P' is the shortest.

[0060] Figure 5 shows an example of the configuration of the evaluation means 42. In step S62, the evaluation means 42 performs the operation of Equation 6 using the subtractor 420 and the divider 422 to obtain the direction vector v(n). Similarly, the direction vector v(r) is obtained using the subtractor 421 and the divider 423. In step S63, the lattice vector calculator 424 performs the operation of Equation 8 to obtain the lattice vector k(n,r). In step S64, the dot product calculator 425 performs the dot product operation between the lattice vector k(n,r) shown in Equation 10 and the estimated relative position vector P' to obtain the theoretical double phase difference Φ(n,r,P'). In step S65, the phasor difference calculator 426 calculates the difference between the double phase difference shown in Equation 11 and the theoretical double phase difference to obtain the evaluation index E(n,r,P').

[0061] As explained above, the relative position detection method of the present invention does not use the integer bias obtained by conventional methods. Therefore, the positioning calculation is completed in a single measurement. Furthermore, it is not necessary to calculate the integrated phase by integrating the phases as done in conventional methods, and it is possible to limit the range of instantaneous phase change to 0 to 2π. As a result, the phase detection device 3 of the present invention can reduce the amount of information transmitted to the positioning means 4.

[0062] [Configuration of the phase detection device] Figure 6 shows the configuration of a phase detection device 3 according to an embodiment of the present invention. The phase detection devices 3, which are installed at multiple measurement points, receive satellite radio waves obtained by the receiving antenna 2, detect the instantaneous phase (φ(1), φ(2), φ(3), φ(M)) of the carrier wave at a predetermined time Ts, and transmit the instantaneous phase to the positioning means 4 via the data transmission unit 35.

[0063] The phase detection device 3 consists of a front end 30, a satellite signal receiving unit 31, a time error acquisition unit 32, an instantaneous phase calculation unit 33, a timing generation means 34, a data transmission unit 35, and an antenna 36. Of these, the satellite signal receiving unit 31 and the instantaneous phase calculation unit 33 are installed for each satellite. Although only satellite (n) is shown as an example in Figure 6, in reality the same signal processing is applied to each of the M satellites.

[0064] In Figure 6, the front-end 30 filters out the weak signal captured by antenna 2, amplifies it, converts it into a low-frequency signal, and supplies it to multiple satellite signal receiving units 31. The satellite signal receiving unit 31 outputs the code information (n), pseudo-distance Pr (n), carrier phase Ω (n), and carrier frequency offset Dp (n) for each satellite (n). Of these, the frequency offset Dp (n) is generally called the "Doppler frequency". The time error acquisition unit 32 uses the code information (n) to perform GNSS reception processing and determines the position (X(n), Y(n), Z(n)) of each satellite (n) and the position (Xa, Ya, Za) of receiving antenna 2. The time error acquisition unit 32 uses this information to calculate and output the time error Δ(n) of the radio waves received from each satellite (n) using the following equation 12.

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[0065] The timing generation means 34 consists of a crystal oscillator and a counter, and supplies the operating clock for the satellite signal receiving unit 31. Since the power consumption of the satellite signal receiving unit 31 increases in proportion to the operating clock frequency, an operating clock with the lowest possible frequency is desirable. Commercially available GNSS receivers use low frequencies such as 1 kHz. The timing generation means 34 also counts the operating clock and outputs a device time Tr. The device time Tr includes a time error equal to the period of the operating clock (the reciprocal of the frequency). (If the operating clock is 1 kHz, it includes a maximum error of 1 ms). The device time Tr also includes further time errors due to the time it takes for radio waves from each satellite to reach antenna 2.

[0066] Therefore, the multiple instantaneous phase calculation units 33 correct the influence of time errors included in the carrier phase Ω(n) sampled at the device time Tr, and output the corrected carrier phase (i.e., instantaneous phase φ(n)) at a predetermined time Ts.

[0067] Figure 7 is a block diagram showing the configuration of the instantaneous phase calculation unit 33. The correction time detection means 331 calculates and outputs the phase correction time δ from a predetermined time Ts that matches UTC, the device time Tr, and the time error Δ(n) according to the following equation 13. ( Number 13 ) δ(n)=Ts- Tr +Δ(n) ...

[13]

[0068] Based on the above, the phase correction means 332 obtains the instantaneous phase φ(n) according to the following equation 14.

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[0069] Figure 8 schematically shows the processing waveform of the instantaneous phase calculation unit 33. If the carrier wave is the waveform shown in (A), the carrier wave phase φ shown in (B) is detected by the phase detection circuit (not shown) inside the satellite signal receiving unit 31. Since this carrier wave phase is convolved in the range of 0 to 2π, the integrated phase Ω shown in (C) is obtained by adding 2π each time it changes from 2π to 0. The goal is to sample the integrated phase Ω at a predetermined time Ts, but since the operating clock frequency cannot be increased in order to reduce power consumption, actual sampling is accompanied by a time error. This sampling time accompanied by a time error is schematically represented as Tr. Here, the frequency offset Dp(n) represents the slope of the integrated phase Ω.

[0070] The correction calculation in Equation 14 approximates the integrated phase as changing linearly with a slope Dp(n) and corrects it to determine the instantaneous phase φ(n) at a given time Ts. It is of course possible to further improve accuracy by approximating the integrated phase with a higher-order polynomial.

[0071] The phase detection device 3 shown in Figure 6 outputs the instantaneous phases (φ(1) to φ(M)) of all satellites (Sat1 to SatM) to the data transmission unit 35. The data transmission unit 35 wirelessly transmits the instantaneous phases to the positioning means 4 via the antenna 36, ​​and the positioning means 4 is configured to perform the positioning calculations described above.

[0072] Figure 9 shows an example of the configuration of payload information transmitted by the phase detection device 3. In this figure, the first two bytes are the header, consisting of an ID number (8 bits) pre-assigned to the phase detection device 3, battery level (4 bits), and the number of satellites successfully received M (4 bits).

[0073] The latter half of the payload information consists of the instantaneous phase detected from each satellite. Specifically, a total of 16 bits are assigned to each satellite: satellite number (6 bits), CNR (2 bits), and instantaneous phase (8 bits). Here, CNR (Carrier to Noise Ratio) is an index representing the carrier wave strength. It is set to "11" when the radio wave strength from the satellite is strong and a good instantaneous phase is expected, and to "10" or "01" for moderate strength. If the satellite is not received, the CNR is set to "00".

[0074] In the example payload information configuration shown in Figure 9, instantaneous phases and headers obtained from up to seven satellites (M=7) can be combined into a 128-bit payload. If ELTRES is used as the LPWA wireless communication method, the payload that can be transmitted in a single transmission is 128 bits, so the payload information in Figure 9 can be transmitted in one transmission. (ELTRES is a registered trademark of Sony Corporation). Because the amount of information transmitted by this invention, which transmits instantaneous phases, is small, LPWA wireless communication can be applied.

[0075] [Confirmation through simulation] I conducted a simulation to verify the principle, and I will now present the results. In this simulation, I assumed a baseline length R = 1.6m and that instantaneous phase data could be obtained from a total of 7 (M = 7) GNSS satellites. Since there are 7 satellites, the total number of satellite pair combinations is 21 (7C2).

[0076] Figure 10 shows plots of evaluation indices for three different satellite pairs (2,1), (3,1), and (3,2) as the baseline length R is varied. It can be confirmed that all three evaluation indices (A), (B), and (C) show a minimum value of "0" at the correct baseline length (R=1.6m). Furthermore, the evaluation index E(3,2) for satellite pair (3,2) has a period of more than 2m. For this satellite pair, because the evaluation index has a long period, there is a possibility that accurate positioning can be achieved even if the movement distance of antenna 2B is large. On the other hand, since the evaluation index E(3,2) changes slowly, there is a possibility that the variation in positioning results will increase due to the influence of noise.

[0077] Therefore, we added up all the evaluation indices obtained from the 21 satellite pairs and plotted the overall evaluation index Ex(R), which is shown in Figure 11. It was found that the overall evaluation index Ex(R) becomes 0 only at the correct baseline length (R=1.6m), confirming that the relative position detection method of the present invention is correct.

[0078] [Experimental verification] Figure 12 shows the results of measuring the baseline length R by applying the present invention to antennas 2A and 2B installed 9.55m apart on the roof of a building. In this experiment, a total of 9 GNSS satellites were received (M=9). The total number of satellite pair combinations was large at 36 (=9C2). As can be seen from the results in Figure 12, the overall evaluation index Ex(R) becomes almost zero when the baseline length is correctly 9.55m, indicating that positioning is being performed correctly. From this, the positioning method of the present invention has been experimentally confirmed.

[0079] [Embodiment 2] In Embodiment 1 described above, the intended use was disaster detection such as landslides, so the central position vector P0 could be determined assuming that the installation positions of antennas 2A and 2B were roughly known. However, there are also application examples other than disaster detection, in which case the positions of antennas 2A and 2B may not be known in advance. Therefore, an example in which the positions of antennas 2A and 2B are determined by code positioning will be described below as Embodiment 2. Note that the explanation of parts that are the same as in Embodiment 1 will be omitted.

[0080] Figure 13 shows an example configuration of the relative position detection system 1B according to Embodiment 2. As in Embodiment 1, the instantaneous phase is detected by the phase detection devices (3A and 3B), and the positioning means 4 outputs the relative position vector P' between the antennas (2A, 2B). In Embodiment 2, the two phase detection devices (3A and 3B) perform code positioning to obtain the coordinates (latitude, longitude, and altitude) of the approximate positions of antennas 2A and 2B and transmit them to the positioning means 4. The positioning means 4 converts these coordinates into a geocentric Cartesian coordinate system and can estimate the center position vector P0 from the relative positions of the two antennas. As a result, it is no longer necessary to know the positions of antennas 2A and 2B in advance, and it can be applied, for example, to positioning moving objects.

[0081] Figure 14 shows an example configuration of the phase detection device 3 according to Embodiment 2. The time error acquisition unit 32 performs code positioning and sends the latitude, longitude, and altitude information of the antenna 2 to the data transmission unit 35. Using the latitude, longitude, and altitude information sent from the data transmission unit 35, the positioning means 4 can determine the center position vector P0.

[0082] Figure 15 shows an example of the configuration of payload information transmitted by the phase detection device 2 according to Embodiment 2. The first 78 bits are a header, which includes an ID number (8 bits), followed by information on the latitude (24 bits), longitude (24 bits), and altitude (12 bits) of the positioned antenna 2. By using 24 bits for latitude and longitude information, the position of antenna 2 can be specified with an accuracy of several meters at any location on Earth.

[0083] The payload in Figure 15 has a total length of 142 bits when the number of satellites M is 4. When the number of satellites M increases to 11, the payload length becomes 254 bits. Since the amount of data that can be transmitted at once with ELTRES is 128 bits, it is necessary to transmit it in two parts, but this is a practical amount of information.

[0084] Although the configuration of the present invention has been described above, it is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0085] In the embodiments described above, the instantaneous phase was explained using radians as the unit. However, by dividing the instantaneous phase by the constant 2π, the unit can also be defined as one rotation of the phase. In this case, the instantaneous phase varies within the range of 0 to 1.

[0086] In the embodiments described above, it was explained that all possible combinations of satellite pairs are used. For example, when the number of satellites M = 9, two satellites are selected from the 9 satellites to form satellite pairs, so the total number of possible combinations of satellite pairs is 36 (9C2). Here, it is not necessarily required to use "all" of the 36 combinations, and some of them can be excluded. For example, the angle η between satellite pairs can be examined, and only satellite pairs with a large η can be excluded from positioning. Alternatively, only satellites with high noise can be determined from the CNR and excluded.

[0087] In the above embodiment, the estimated relative position vector P' with the smallest overall evaluation index Ex(P') is output as the positioning result. However, it is also possible to obtain, for example, the estimated relative position vector P1' with the smallest overall evaluation index Ex(P') and the estimated relative position vector P2' with the second smallest overall evaluation index Ex(P'), and then use other information such as the movement status of antenna 2B to output either P1' or P2' as the positioning result.

[0088] In the embodiments described above, it was assumed that the carrier frequency transmitted from the satellite was approximately 1.5 GHz, but there are also satellites that use a 1.2 GHz carrier. By applying the present invention using two types of carriers, 1.5 GHz and 1.2 GHz, even higher precision measurements become possible.

Claims

1. Multiple antennas, A phase detection device connected to each of the aforementioned multiple antennas receives radio waves from multiple GNSS satellites and detects the instantaneous value of the carrier phase, The system includes positioning means for determining the relative position vector between the plurality of antennas using the instantaneous value of the carrier phase, The positioning means is A dual phase difference calculation means calculates the difference in the instantaneous values ​​of the carrier phase for a pair of satellites consisting of two satellites extracted from the plurality of GNSS satellites to obtain a dual phase difference, A means for acquiring satellite position information to acquire the satellite position of the GNSS satellite, An evaluation means for determining an evaluation index for the relative position vector using the dual phase difference and the satellite position, A comprehensive evaluation means that calculates a comprehensive evaluation index by integrating the evaluation indexes for different satellite pairs. A relative position detection system characterized by including, The phase detection device is A satellite signal receiving unit that receives radio waves transmitted from the plurality of GNSS satellites and detects the carrier phase, carrier offset frequency, code information, and pseudo-distance of the plurality of GNSS satellites at the time of the device, A time error acquisition unit that uses the code information and the pseudo-distance to determine the time error of the radio waves, An instantaneous phase calculation unit calculates the instantaneous value of the carrier phase at a predetermined time by correcting the carrier phase using the carrier offset frequency and time error obtained from the satellite signal receiving unit. A data transmission unit that transmits the instantaneous value of the carrier phase, A relative position detection system including...

2. The evaluation means is A grid vector calculation means for determining the grid vectors related to the aforementioned pair of satellites, A theoretical double difference calculation means calculates the dot product of the lattice vector and the relative position vector to obtain the theoretical double phase difference, The relative position detection system according to claim 1, characterized in that it includes a phase difference evaluation means that evaluates the difference between the theoretical double phase difference and the double phase difference and outputs the evaluation index.

3. The relative position detection system according to claim 1 or 2, characterized in that the comprehensive evaluation by the comprehensive evaluation means uses evaluation indicators for all possible combinations of satellite pairs.

4. The relative position detection system according to claim 1 or 2, characterized in that the instantaneous value of the carrier phase has a change range within 2π radians.

5. The relative position detection system according to claim 1, characterized in that the instantaneous phase calculation unit limits the instantaneous value of the carrier phase to a range of 0 to 2π radians.

6. The relative position detection system according to claim 1, characterized in that the data transmission unit transmits position information detected from the code information in addition to the instantaneous value of the carrier phase.

7. The time error acquisition unit determines the time error as the difference between the distance from the GNSS satellite to the position of the receiving antenna of the phase detection device and the pseudo-distance, divided by the speed of light, and the transmission delay time of the GNSS satellite obtained from the code information. The relative position detection system according to claim 1.

8. A phase detection procedure for detecting the instantaneous value of the carrier phase by receiving radio waves from multiple GNSS satellites using multiple phase detection devices connected to multiple antennas, and A positioning procedure for determining the relative position vector between antennas using the instantaneous value of the carrier phase, A relative position detection method including, The aforementioned positioning procedure is: A procedure for determining the double phase difference using the instantaneous value of the carrier phase for the satellite pair, A procedure for obtaining the satellite positions of the aforementioned multiple GNSS satellites, A procedure for determining an evaluation index for the relative position vector using the dual phase difference and the satellite position, A procedure for comprehensively evaluating the evaluation indicators for multiple satellite pairs and obtaining the relative position vector as the positioning result. Includes, The aforementioned phase detection procedure is: A satellite signal reception procedure for receiving radio waves transmitted from the aforementioned multiple GNSS satellites and for detecting the carrier phase, carrier offset frequency, code information, and pseudo-distance of the multiple GNSS satellites at the time of the device, A time error acquisition procedure for determining the error in the device time using the code information and the pseudo-distance, An instantaneous phase calculation procedure that uses the carrier offset frequency and the device time error obtained in the satellite signal reception procedure to correct the carrier phase and calculate the instantaneous value of the carrier phase at a predetermined time, A data transmission procedure for transmitting the instantaneous value of the carrier phase, A relative position detection method characterized by including the following:

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