JPH06342053A - Three-dimensional positioning system by gps receiver using gps satellite and geostationary satellite - Google Patents

Abstract

PURPOSE:To enhance the accuracy of a distance measurement by a method wherein the position of a satellite in every moment is monitored, the error of the position of the satellite and the state of the ionosphere and of an atmospheric gas layer are always grasped and a propagation error due to them is corrected. CONSTITUTION:A receiver for a large-sized ground station provided with a parabola antenna is installed in a spot whose latitude, longitude and altitude have been decided. The propagation time of radio waves from a satellite and an angle of elevation at the time when the radio waves have arrived are measured. The refractive index of the ionosphere and of an atmospheric gas layer in a propagation route from the satellite up to the receiver is found. Then, the position at every moment of the satellite is measured. The measurements are repeated at certain time intervals, and position data, on the satellite, which corresponds to the found time is transmitted to the whole country. A surveyor puts a GPS receiver in a measuring point, the receives radio waves from a geostationary satellite, he aquires the radio-wave propagation time and the position data on the satellite, and he computes the position of the measuring point. Then, the pulse signal of a GPS satellite is received, a clock error is corrected on the basis of the measured reception time, and the position of the measuring point is decided.

Description

Detailed Description of the Invention

In the present technology, the position of the satellite at each moment is monitored, and the states of the ionosphere and atmospheric gas layer are constantly grasped. The purpose is to eliminate the propagation error that occurs and improve the accuracy of distance measurement.

2. Description of the Related Art In a single positioning in which radio waves from GPS satellites are received by a receiver on the ground to determine a three-dimensional position, satellite orbit information, radio wave propagation paths (ionosphere and atmospheric gas layer), a satellite together with a receiver. Due to the error of the above clock, it is said that the C / A code has a nominal accuracy of 100 m and the P code has a nominal accuracy of 16 m. Further, in relative positioning in which radio waves from GPS satellites are measured by a plurality of receivers and a relative positional relationship between reception points is obtained, with accuracy of several cm to several m,
Although the accuracy is remarkably improved as compared with the single positioning, there is a disadvantage that the measurement recording time of 15 minutes or more and about 2 hours is required, and the result cannot be obtained in a short time.

[Industrial Application Field and Effect of Invention]

1. Positioning of ships, cars, trains, and aircraft 2. Application to geodetic survey 3. Application to large-scale civil engineering 4. Application to monitoring deformation and movement of structures 5. Application to scientific observation (earthquake / volcanic eruption prediction, movement of plate technics) 6. Application to ocean observation and observation in space With the development of this technology, three-dimensional position measurement can be performed instantaneously and at the level of distance measurement accuracy mm. Will be replaced.

[Means for solving problems]

[Operation] A large ground station receiver with a parabolic antenna is placed at a location where the latitude, longitude, and height are fixed. The receiver's clock is synchronized with Greenwich Mean Time, Sunday midnight. Also, the time from when the head of the first sub-frame of the received data is read to when the head of the second sub-frame is read is measured by receiving the radio wave from the satellite. The difference between the measurement time and 6 seconds is detected, and the detected value is corrected as the clock shift of the receiver. The pattern of C / A codes from GPS satellites is unique to each satellite and is 1.023 MBPS. Radio waves from GPS satellites are considered as pulse signals consisting of one bit to several bits, and the reception time of each pulse at the receiver is measured. Each pulse signal is numbered, and as shown in FIG. 3, 1, 2, ... i, and the reception time of each pulse signal is T _A1 , T _A2 , ...
..., T _Ai . If the reception time of the pulse signal 1 is accurately measured, the reception times of the other pulse signals 2, ..., I are naturally determined. Therefore, the time required to receive 1000 pulse signals is (1 / 1.023 × 10 ⁶ ) × 1000 to (5 / 1.023 × 10 ⁶ ) × 1000 (s) 10 ^{−3 to} 5 × 10 ⁻³ (s) Further, the elevation angle of each pulse when it reaches the receiver antenna is measured. The elevation angle of each pulse signal when it reaches the receiver antenna is
_11, α _{21, ····,} and α _i1. If the elevation angle α _{11 of the} pulse signal is accurately measured, the remaining elevation angle α ₂₁ ,
..., α _{i1 is} also accurately measured. As a result, the thickness h parallel to the horizontal plane passing through the position of the receiver near the radio path between the satellite and the receiver of the atmospheric gas layer (including the ionosphere).
The refractive index of the parallel plane layer of (1 km) is obtained. For details, refer to Japanese Patent Application No. 3-128489 (submitted April 30, 1991).
Date, submission of amendment See August 20, 1991, "Measurement of Refractive Index of Atmospheric Gas Using Radio Wave Propagation". Therefore, the refractive index of the parallel plane layer of the thickness h (1 km) of the atmospheric gas layer (including the ionosphere) near the radio path connecting the four satellites and the receiver on the ground surface is (10 ⁻³ + τ). Xu) × 4 to (5 × 10 ⁻³ ) + τ × u) (s). (However, τ is a calculation time of one simultaneous equation of 100 yuan and u is the number of times of simultaneous equations of 1000 yuan is calculated.) When the refractive index of the atmospheric gas layer (including the ionosphere) near the radio wave path is calculated, the latitude is calculated. Place a GPS receiver at the point where the longitude, height, and height are fixed. This receiver receives the radio wave from the satellite and measures the time from when the head of the first sub-frame of the received data is read to when the head of the second sub-frame is read. The difference between the measurement time and 6 seconds is detected, and the detected value is corrected as the clock shift of the receiver. Also, the clock of this receiver is in the form of an external connection and is synchronized with Greenwich Mean Time, midnight Sunday. Radio waves from four satellites are received, the arrival time of this radio wave at this receiver is detected, and the propagation time from each satellite is measured. As a result, the position of each satellite at a certain time is determined. For details, see Japanese Patent Application No. 3-12320.
5 (Submit March 4, 1991, submit amendment August 2, 1991
See "3D position measurement by communication satellite" on the 0th. In this way, the position of the satellite at a fixed time interval is fixed,
These position data are transmitted nationwide via a geostationary satellite located 36000 km above the equator. Each surveyor has a GPS
Place the receiver at the measuring point. The clock of this GPS receiver measures the time from when the radio wave from the satellite is received and the beginning of the first sub-frame is read to when the beginning of the second sub-frame is read. Six seconds is detected, and the detected value is corrected as the clock shift. Next, the radio wave (C / A code) from the GPS satellite is considered as a pulse signal consisting of one bit to several bits, the reception time of each pulse at the GPS receiver is measured, and the measurement point and each satellite are connected. Atmospheric gas layer near the radio path (including the ionosphere)
The refractive index of is measured within 1 minute. With this, the horizontal and vertical distances from the measurement point to each satellite can be obtained. However, since the position of each satellite has already been determined, the position of the measurement point can be obtained. Therefore, the measurement points thus obtained are supposed to match, or do not match because of an error in the clock of the GPS receiver. Now, the position of each satellite is (x _i , y _i , z _i ), the position of the measurement point is (x ₀ , y ₀ , z ₀ ), the linear distance between each satellite and the measurement point is r _i , GPS Assuming that the distance traveled between the errors of the receiver clock is s, (x _i −x ₀ ) ² + (y _i −y ₀ ) ² + (z _i −z ₀ )
² = (r _i + s) ² However, the medium is assumed to be vacuum. As a result, the true position of the measurement point in which the error of the clock or the like of the GPS receiver is corrected can be obtained. ◆ 1 Measurement of Radio Refractive Index of Ionosphere and Atmospheric Gas Layer The atmosphere around the earth is divided into atmospheric gas layer, ionosphere and radio wave straight layer. The atmospheric gas layer and the ionosphere are not treated individually, but are collectively referred to as the atmospheric gas layer (including the ionosphere). Atmospheric gas layer (including ionosphere) is 10 from the ground surface
The area up to 00 km is set, and the area higher than this is set as the radio wave straight traveling layer. The atmospheric gas layer (including the ionosphere) is divided into parallel plane layers of thickness h (1 km) parallel to the horizontal plane passing through the receiver on the ground surface. (See FIG. 2) At time T _Pi , the radio wave radiated from the satellite position Pi toward the receiver on the ground surface propagates and reaches the receiver position Ai at time T _Ai ( Hereinafter, this radio wave is referred to as radio wave; Pi → Ai). Radio wave; Pi → Ai
Is a radio wave when it enters the interface between the radio wave rectilinear layer and the atmospheric gas layer (including the ionosphere); the incident angle of Pi → Ai is α _i0 ,
The atmospheric gas refractive index at the point Ai is n ₁ , the atmospheric pressure at the point Ai is p,
If the temperature is T and the vapor pressure is e, For details of the formula, see Japanese Patent Application No. 3-123205.
See "4. Elevation angle determination". Radio wave at point Ai; if the elevation angle of Pi → Ai is α _i1 , then Snell's law From the formula, n ₁ is determined. n ₀ is the refractive index of a radio wave in vacuum. Since α _i1 is a measured value, COS _i1 is determined, and COS α _i0 is also determined from the equation. Or ◆ 4
Method to determine cos α _i0 . Transform the expression, Then, the right side of the formula is fixed. By repeating the above operation n times, the following n-ary simultaneous simultaneous equations are established. For details of the establishment of this simultaneous equation, see Japanese Patent Application No. 3-
128489 (Submitted April 30, 1991, Submitted amendment August 20, 1991 See "Measurement of Refractive Index of Atmospheric Gas Using Radio Wave Propagation". Refractive coefficient; k _ij is The initial value of the refractive index of each parallel plane layer of the atmospheric gas layer (including the ionosphere) is the refractive index of the USA standard atmospheric model of the atmospheric gas layer (including the ionosphere) in the zenith direction at the measurement point. Further, the refractive index; k _ij is the atmospheric gas layer in the zenith direction at the measurement point (including the ionosphere) in n _j of the equation.
Substituting the refractive index of the USA standard atmosphere model of, the initial value. These values are substituted into the n-ary simultaneous equations to solve. This solution is the first approximation of the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path between the satellite and the receiver. The first-order approximation value of this refractive index is substituted into the equation to obtain the first-order approximation value of the refraction coefficient of the atmospheric gas layer (including the ionosphere) near the radio path between the satellite and the receiver. An n-ary simultaneous equations consisting of this refractive index is solved, and this solution is used as the second approximate value of the refractive index. The second approximate value of the refractive index is substituted into the formula to obtain the second approximate value of the refractive index. The above operation is repeated several times to obtain the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path between the satellite and the receiver. ◆ 2 Position determination of satellite Let _{P be} the position of satellite at time T _P , and its coordinate be P
(X, Y, Z). Times at which the radio waves radiated from the satellite position P at time T _P reach the receiver on the ground surface are designated as T _A and T _B, and the positions of the receiver at this time are designated as A and B, respectively. Let Q be a foot of a perpendicular line drawn from the point P to the xy-plane. (However, the receivers at points A and B are the same. See Fig. 2.) A parallel plane layer with a thickness of 1 km of the atmospheric gas layer (including the ionosphere) near the radio path connecting the satellite and the receiver. Refractive index of n
_i ( _{i = 1 to 1000} ) has been determined (refer to ◆ measurement of radio wave refractive index of ionosphere and atmospheric gas layer). Satellite position P
Radio waves radiated from the antenna and reaching position A of the receiver (radio wave P
→ Called A. ) Enters the interface between the radio wave straight layer and the atmospheric gas layer (including the ionosphere), the incident angle is α ₀ , the radio wave radiated from the satellite position P and reaching the receiver position B (radio wave P → B .) When it enters the interface between the radio wave rectilinear layer and the atmospheric gas layer (including the ionosphere) is β ₀ . The radio path length of radio wave P → A is The radio path length from radio wave P to B is However, L is the height from the xy-plane of the satellite and has been determined. From, far. From the formula, (11), From the formula, (12), Substituting equations (10) and (13) into equation (14). In equation (15), c: propagation velocity of radio wave v: rotation velocity of earth p: propagation velocity of radio wave P → A h: parallel plane of atmospheric gas (including ionosphere) parallel to horizontal plane passing through receiver position The layer thickness is 1 km. k _i : refractive index near the path of the radio wave P → A, n _i : Refractive index in the vicinity of the path of the radio wave P → A L: Height from the xy-plane of the satellite Since all have been determined, cos β ₀ is determined. Therefore, β _{0 is} also determined. The rotation direction of the earth is y
It is assumed to be parallel to the axis. Let γ and δ be the angles formed by the straight lines AQ and BQ and the x axis (see FIG. 2). However, α _i and β _i are xy− passing through the positions A and B of the receiver.
It is a refraction angle of a radio wave passing through a parallel plane layer of an atmospheric gas layer (including an ionosphere) having a thickness h (1 km) parallel to the plane. Then, A, B and C are determined. For details, refer to Japanese Patent Application No. 3-123205 (submitted 1991 March).
April 4, submission of amendment August 20, 1991 "Refer to" 6 azimuth measurement "of 3D position measurement by communication satellite"
Therefore, γ and δ are also determined. Therefore, the position of the point P is fixed. ◆ Using satellites with 3 fixed positions, satellite and GP
S A method for measuring the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path that connects the receiver (a method for obtaining the refractive index without measuring the elevation angle of the received radio wave). The position of the satellite at time T _P1 is P1. The radio wave radiated from the point P1 reaches the GPS receiver at time T _A1 , and the position of the GPS receiver at this time is A1.
From the radio wave received by the GPS receiver, the position data of the satellite that radiated this radio wave can be known. By receiving radio waves from each satellite whose position is known, the approximate position of the GPS receiver can be determined. With the position of this GPS receiver as the origin, the position coordinate of one of the satellites is now (Lx,
Ly, Lz), However, from p = T _A1 −T _P1 formula (17), Substituting equation (18) into equation (16), By repeating such an operation to be obtained 1000 times, 1000 pieces of cos α _i and propagation time p _i are obtained. From these, ◆ 1 The first-order approximation of the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path connecting the satellite and the measurement point can be obtained by the method of measuring the radio refractive index of the ionosphere and atmospheric gas layer. . Therefore, the horizontal distance and the vertical distance from the measurement point to the satellite can be obtained. Since the position of the satellite has been fixed, the position of the measurement point can be known. From the first-order approximation value of this refractive index, the second approximation value of cos α _i is obtained,
Further, the second approximate value of the refractive index is obtained, and gradually approaches the true value of the refractive index. ◆ 4 A method of measuring the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path connecting the satellite and the GPS receiver, using a satellite whose position is known. (A method of obtaining the refractive index by measuring the elevation angle of the received radio wave.) Radio waves from four satellites in the sky are received, and the approximate position where the GPS receiver is placed is determined. With the position of this GPS receiver as the origin, and the vertical distance to one satellite in the sky is L _z , For details of the establishment of the above two formulas, see Japanese Patent Application No. 3-12320.
5 (Submit March 4, 1991, submit amendment August 2, 1991
0th day “Three-dimensional position measurement by communication satellite” “3 Correction of satellite position error due to atmospheric refractive index”, “4 Measurement of elevation angle”
From the above two equations, hΣ _i ⁼ 1 n _{k i,} since being approximately as a function of cos [alpha] _0, the equation ▲ 20 ▼, by repeating 1000 times such an operation that cos [alpha] ₀ is obtained, 10
The 00 cos α _i and the propagation time p ⁱ are obtained. From these, ◆ 1 The first-order approximation of the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path connecting the satellite and the measurement point can be obtained by the method of measuring the radio refractive index of the ionosphere and atmospheric gas layer. . Therefore, the horizontal distance and the vertical distance from the measurement point to the satellite can be obtained. Since the position of the measurement point has already been determined, the satellite position can be known. The second approximate value of cos α _i is obtained from the first approximate value of the refractive index, and the second approximate value of the refractive index is further obtained, and gradually approaches the true value of the refractive index.

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[Procedure amendment]

[Submission date] November 2, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Name of the invention GPS using GPS satellites and geostationary satellites
3D positioning system with receiver

[Claims]

Detailed Description of the Invention

[0001]

In the present technology, the position of the satellite at each moment is monitored, and the states of the ionosphere and atmospheric gas layer are constantly grasped. The purpose is to eliminate the propagation error that occurs and improve the accuracy of distance measurement.

[0002]

2. Description of the Related Art In a single positioning in which radio waves from GPS satellites are received by a receiver on the ground to determine a three-dimensional position, satellite orbit information, radio wave propagation paths (ionosphere and atmospheric gas layer), a satellite together with a receiver. Due to the error of the above clock, it is said that the C / A code has a nominal accuracy of 100 m and the P code has a nominal accuracy of 16 m. In relative positioning, which measures the radio waves from GPS satellites with multiple receivers and finds the relative positional relationship between the receiving points, the accuracy is about several cm to several meters, which is more accurate than the single positioning. Is remarkably improved, but there is a disadvantage that the measurement recording time of 15 minutes or more and about 2 hours is required, and the result cannot be obtained in a short time.

[0003]

[Industrial Application Field and Effect of Invention] 1. Positioning of ships, cars, trains, and aircraft 2. Application to geodetic survey 3. Application to large-scale civil engineering 4. Application to monitoring deformation and movement of structures 5. Application to scientific observation (earthquake / volcanic eruption prediction, movement of plate technics) 6. Application to ocean observations and observations in space With the development of this technology, three-dimensional position measurement can be performed instantly and with a range-finding accuracy of mm, and future surveying systems will be fully equipped with positioning systems using this technology. Will be replaced.

[0004]

[Means for solving problems]

[Operation] There are two cases, one is to measure the elevation angle when the radio wave from the satellite reaches the receiver, and the other is to measure it without measuring the elevation angle. First, when measuring the elevation angle, place the receiver of a large ground station equipped with a parabolic antenna at a location where the latitude, longitude, and height are fixed. If you do not measure the elevation angle of the received radio wave,
A GPS receiver is placed at the point where this position is fixed. The receiver's clock is synchronized with Greenwich Mean Time, Sunday midnight. Also, from the time of receiving the radio wave from the satellite and reading the beginning of the first subframe of the received data,
The time until the beginning of the second subframe is read is measured. The difference between the measurement time and 6 seconds is detected, and the detected value is corrected as the clock shift of the receiver. G
The C / A code pattern from the PS satellites is 1.023MBPS, which is unique to each satellite. Radio waves from GPS satellites are considered as pulse signals consisting of one to several bits, and the reception time of each pulse at the receiver is measured. Each pulse signal is numbered, and as shown in FIG. 3, 1, 2, ... i, and the reception time of each pulse signal is T _A1 , T _A2 , ...
・, T _Ai . If the reception time of the pulse signal 1 is accurately measured, the reception times of the other pulse signals 2, ..., I are naturally determined. Therefore, the time required for receiving 1000 pulse ^{signals, (1 / 1.023 × 10 6} ) × 1000 ~ (5 / 1.023 × 10 6) × 1000 (s) 10 - 3 ~ 5 × 10 - 3 ( s) Also, measure the elevation angle of each pulse when it reaches the receiver antenna. The elevation angle of each pulse signal when it reaches the receiver antenna is
₁₁ , α ₂₁ , ..., α _i1 . Elevation angle α of pulse signal
_{If the 11} is measured accurately, the remaining elevation angle α ₂₁ , ..., α
_{i1 is} also accurately measured. As a result, it is parallel to the horizontal plane passing through the position of the receiver near the radio path between the satellite and the receiver of the atmospheric gas layer (including the ionosphere) by the method of "◆ 1 Measurement of radio wave refractive index of ionosphere and atmospheric gas layer". Thickness h (1
The refractive index of the parallel plane layer of (km) can be obtained. If you do not measure the elevation angle of each pulse when it reaches the receiver antenna, see “◆ 3
The atmospheric gas layer (including the ionosphere) is measured by the method of measuring the refractive index of the atmospheric gas layer (including the ionosphere) in the vicinity of the radio path connecting the satellite and the GPS receiver using the satellite whose position is fixed. The refractive index of the parallel-plane layer having the thickness h near the radio wave path between the satellite and the receiver can be obtained. For details, see Japanese Patent Application
3-128489 (Submit April 30, 1991, submit amendment Heisei 3
August 20, 2014, "Measurement of Refractive Index of Atmospheric Gas Using Radio Wave Propagation". Therefore, the refractive index of the parallel plane layer of thickness h (1 km) of the atmospheric gas layer (including the ionosphere) near the radio path connecting the four satellites and the receiver on the ground surface is (10 ^-3 + It can be measured within τ × u) × 4 ~ ((5 × 10 ^-3 ) + τ × u) × 4 (s). (However, τ is the calculation time for one-time simultaneous equations of 1000 yuan, u is the number of calculations for simultaneous equations of 1000 yuan) When the refractive index of the atmospheric gas layer (including the ionosphere) near the radio wave path is calculated, the latitude is calculated. Place a GPS receiver at the point where the longitude, height, and height are fixed. This receiver receives the radio wave from the satellite and measures the time from when the head of the first sub-frame of the received data is read to when the head of the second sub-frame is read. The difference between the measurement time and 6 seconds is detected, and the detected value is corrected as the clock shift of the receiver. Also, the clock of this receiver is in the form of an external connection and is synchronized with Greenwich Mean Time, midnight Sunday. Radio waves from four satellites are received, the arrival time of this radio wave at this receiver is detected, and the propagation time from each satellite is measured. As a result, the position of each satellite at a certain time is determined by the methods of ◆ 1 and ◆ 2. For details, refer to Japanese Patent Application No. 3-123205 (submitted March 4, 1991, amendment submitted August 20, 1991, "3D Position Measurement by Communication Satellite". The positions of satellites at fixed time intervals are determined, and these position data are collected over the equator.
It is sent nationwide via a geostationary satellite located at 00km. Each surveyor places a GPS receiver at the measurement point. The clock of this GPS receiver measures the time from when the radio wave from the satellite is received and the beginning of the first sub-frame is read to when the beginning of the second sub-frame is read. The difference from 6 seconds is detected, and this detected value is corrected as the deviation of this clock. Next, the radio wave (C / A code) from the GPS satellite is considered as a pulse signal consisting of one bit to several bits, the reception time of each pulse at the GPS receiver is measured, and the measurement point and each satellite are connected. The refractive index of the atmospheric gas layer (including the ionosphere) near the radio wave path is measured within 1 minute. With this, the horizontal and vertical distances from the measurement point to each satellite can be obtained. However, since the position of each satellite has already been correctly determined, the position of the measurement point can be obtained. Therefore, although the measurement points obtained in this way should match,
It does not match due to an error in the receiver clock. Also, when the position of each satellite is not correctly determined, that is, when the position of each satellite is determined by the navigation message from each satellite,
Compared with the case of using position data corresponding to the time of each satellite via a geostationary satellite, the measurement accuracy is reduced by 1 to 2 levels. Now, the position of each satellite is (x _i , y _i , z _i ), and the position of the measurement point is (x ₀ , y
₀ , z ₀ ), the linear distance between each satellite and the measurement point is r _i , GP
Let s be the distance traveled between the errors of the S receiver clock, (x _i -x ₀ ) ² + (y _i -y ₀ ) ² + (z _i -z ₀ ) ² = (r _i + s) ^{2 With} this, the true position of the measurement point with the error of the clock of the GPS receiver corrected can be obtained from "◆ 5 Method of correcting the error of clock of the GPS receiver".

◆ 1 Measurement of Radio Refractive Index of Ionosphere and Atmospheric Gas Layer The circumference of the earth is divided into an atmospheric gas layer, an ionosphere and a radio wave rectilinear layer. The atmospheric gas layer and the ionosphere are not treated individually, but are collectively referred to as the atmospheric gas layer (including the ionosphere). Atmospheric gas layer (including ionosphere) is 10 from the ground surface
The area up to 00 km is set, and the area higher than this is set as the radio wave straight traveling layer. The atmospheric gas layer (including the ionosphere) is divided into parallel plane layers of thickness h (1 km) parallel to the horizontal plane passing through the receiver on the ground surface. (See FIG. 1) At time T _Pi , the radio wave radiated from the satellite position Pi toward the receiver on the ground surface propagates and reaches the receiver position Ai at time T _Ai ( Hereinafter, this radio wave is referred to as radio wave; Pi → Ai). Radio wave; Radio wave when Pi → Ai rushes into the interface between the radio wave straight layer and the atmospheric gas layer (including the ionosphere); The incident angle of Pi → Ai is α _i0 , the atmospheric gas refractive index at point Ai is n ₁ , the point The atmospheric pressure of Ai is p, the temperature is T,
If vapor pressure is e, then cosα _i0 = hΣ _i , _{j = 1} ⁿ k _ij (1 + n _j ) / {(c ± v) ・ (T _Ai -T _Pi )} Japanese Patent Application No. 3-123205
See "4. Elevation angle determination". n ₁ = 1 + [77.6 × {p / (T + 217.5)} + 3.73 × 10 ⁵ × {e / (T + 217.5) ² ] × 10 ^-6 radio waves at Ai; the elevation angle from Pi to Ai is α _i1 Then, from Snell's law, n ₁・ sin (π / 2-α _i1 ) = n ₀・ sin α _i0 ∴ sin α _i0 = (n ₁ / n ₀ ) cos α _i1 ∴ cos α _i0 = (1-sin ² α _i0 ) ^1/2 = {1- (n ₁ / n ₀ ) ² cos ² α _i1 } ^{1/2 The} n ₁ is determined from the equation. n ₀ is the refractive index of radio waves in a vacuum. Further, since the alpha _i1 is measured, cos [alpha] _i1 is determined, cos [alpha] _i0 also determined from the equation. Or, determine cos α _i0 by the method of ◆ 4. When the formula is transformed to Σ _{i, j = 1} ⁿ k _ij (1 + n _j ) = (1 / h) {(c ± v) (T _Ai -T _Pi )} ・ cos α _i0 , the right side of the formula Is confirmed. By repeating the above operation n times, the following n-ary simultaneous simultaneous equations are established. k ₁₁ n ₁ + k ₁₂ n ₂ + k ₁₃ n ₃ + ・ ・ ・ ・ ・ ・ + k _1n n _n = (1 / h) {(c ± v) (T _A1 -T _P1 )} cos α ₁₀ -Σ _{j = 1} ⁿ k _1j k ₂₁ n ₁ + k ₂₂ n ₂ + k ₂₃ n ₃ + ・ ・ ・ ・ ・ + k _2n n _n = (1 / h) {(c ± v) (T _A2 -T _P2 )} cos α ₂₀ -Σ _{j = 1} ⁿ k _2j・ ・ ・ ・ ・ k _n1 n ₁ + k _n2 n ₂ + k _n3 n ₃ + ・ ・ ・ ・ ・ ・ + k _nn n _n = (1 / h) { (c ± v) (T _An -T _Pn )} cos α _n0 -Σ _{j = 1} ⁿ k _nj For details of the establishment of this simultaneous equation, see Japanese Patent Application No. 3-12.
8489 (Submit April 30, 1991, submit amendment 8 August 1991
See “Measurement of Refractive Index of Atmospheric Gas Using Radio Wave Propagation” on March 20. Also, the refractive index; k _ij is k _ij = {(1-sin ² α _i0 ) / (n _j ² -sin ² α _i0 )} ^1/2 parallel plane layers of the atmospheric gas layer (including the ionosphere) The initial value of the refractive index of is the sum of the refractive index of the atmospheric gas layer (including the ionosphere) in the zenith direction at the measurement point in the USA standard atmospheric model and the refractive index obtained from the electron density of the ionosphere at standard time. The refractive index; k _ij is the US of the atmospheric gas layer (including the ionosphere) in the zenith direction at the measurement point in n _j of the equation.
A The sum of the refractive index of the standard atmospheric model and the refractive index obtained from the electron density of the ionosphere at the standard time is substituted and used as the initial value.
These values are substituted into the n-ary simultaneous equations to solve. This solution is the first approximation of the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path between the satellite and the receiver.
Substituting the first-order approximation value of this refractive index into the formula and
Radio wave; Radio wave when P _i → A _i rushes into the interface between the radio wave straight layer and atmospheric gas layer; First approximation of the cosine of the incident angle of P _i → A _i and the radio wave path between the satellite and the receiver The first-order approximation of the refraction coefficient of the atmospheric gas layer (including the ionosphere). An n-element simultaneous linear equation consisting of this refractive index and the like is solved, and this solution is used as the second approximate value of the refractive index. The second approximate value of the refractive index is substituted into the equations and to obtain the second approximate value of the cosine of the incident angle of the radio wave; P _i → A _i and the refractive coefficient. When the above operations are repeated several times and the calculation converges with the required accuracy, the calculation is terminated and the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path between the satellite and the receiver is obtained.

◆ 2 Satellite Position Determination At the time T _P , the satellite position is P, and its coordinates are P
(X, Y, Z). Times at which the radio waves radiated from the satellite position P at time T _P reach the receiver on the ground surface are T _A and T _B, and the positions of the receiver at this time are A and B, respectively. Let Q be a foot of a perpendicular line drawn from the point P to the xy-plane. (However, the receivers at points A and B are the same. See Fig. 2.) A parallel plane layer with a thickness of 1km of the atmospheric gas layer (including the ionosphere) near the radio path connecting the satellite and the receiver. Refractive index of n _i
(I = 1 to 1000) has been confirmed (refer to ◆ 1 Measurement of radio wave refractive index of ionosphere and atmospheric gas layer). Radio waves radiated from the satellite position P and reaching the receiver position A (radio waves P → A
I call it. ) Enters the interface between the radio wave rectilinear layer and the atmospheric gas layer (including the ionosphere), the incident angle is α ₀ , the radio wave radiated from the satellite position P and reaching the receiver position B (radio wave P → B The angle of incidence when β rushes into the interface between the radio wave rectilinear layer and the atmospheric gas layer (including the ionosphere) is β ₀ . cosα ₀ = {hΣ _{i = 1} ⁿ k _i (1 + n _i )} / {(c ± v) (T _A -T _P )} cosβ ₀ = {hΣ _{i = 1} ⁿ m _i (1 + n _i ) } / {(c ± v) (T _B -T _P )}, the details of the establishment of the formula, Japanese Patent Application No. 3-123205
March 4, 2014, submission of amendment, August 20, 1991, refer to “3D Position Measurement by Communication Satellite” “4 Elevation Angle Measurement”. Telecommunications path length of the radio wave P → A ^{_{is, hΣ i = 1 n (1}} / cosα i) + (L-nh) / cosα 0 = hΣ i = 1 n (cosα 0 / cosα i) (1 / cosα 0) + (L-nh) / cosα ₀ = (hΣ _{i = 1} ⁿ k _i n _i ) (1 / cosα ₀ ) + (L-nh) / cos α ₀ = (hΣ _{i = 1} ⁿ k _i n _i + L-nh ) / cos [alpha] ₀ Telecommunications path length of the radio wave P → B ^{_{is, hΣ i = 1 n (1}} / cosβ i) + (L-nh) / cosβ 0 = (hΣ i = 1 n m i n i + L-nh) / cosβ ₀ However, L is already determined by the height from the xy-plane of the satellite. From, T _A -T _B = ((hΣ _{i = 1} ⁿ k _i n _i + L-nh) / cos α _0- (hΣ _{i = 1} ⁿ m _i n _i + L-nh) / cos β ₀ } ( 1 / c) = (hΣ _{i = 1} ⁿ k _i n _i + L-nh) (1 / cosα ₀ -1 / cosβ ₀ ) (1 / c) (10) │k _i = ((1-sin ² α ₀ ) / (n _i ² -sin ² α ₀ )} ^1/2 ∵│m _i = {(1-sin ² β ₀ ) / (n _i ² -sin ² β ₀ )} ^1/2 │α ₀ ≈ Let β ₀ │ k _i ≈m _i T _A -T _P = p (11) T _B -T _P = p + Δt (12). From equation (11), cosα ₀ = {hΣ _{i = 1} ⁿ k _i (1 + n _i ) / (c ± v) p} (13) From equation (12), cosβ ₀ = {hΣ _{i = 1 ^{n m i (1 + n i}} ) / (c ± v) (p + Δt)} (14) equation (14) into equation (10), substituting (13). cosβ ₀ = hΣ _{i = 1} ⁿ m _i (1 + n _i ) / [(c ± v) 〔p + {-(hΣ _{i = 1} ⁿ k _i n _i + L-nh) / cos α ₀ + (hΣ _{i = ^{1 n k i n i + L}} -nh) / cosβ 0} (1 / c) _{]] (∵ k i ≒ m i} ) = hΣ i = 1 n k i (1 + n i) / [(c ± v ) (P + {-hΣ _{i = 1} ⁿ k _i n _i + L-nh) (c ± v) p / hΣ _{i = 1} ⁿ k _i (1 + n _i ) + (hΣ _{i = 1} ⁿ k _i n _{i + L-nh) / cosβ 0} } (1 / c) _{]] (∵ k i ≒ m i} ) ∴ (c ± v) p · cosβ 0 - {(hΣ i = 1 n k i n i + L-nh ) (c ± v) ² p} / {hcΣ _{i = 1} ⁿ (1 + n _i )} ・ cosβ ₀ + (c ± v) (hΣ _{i = 1} ⁿ k _i n _i + L-nh) / c = hΣ _{i = 1} ⁿ k _i (1 + n _i ) ∴ [(c ± v) p-{(hΣ _{i = 1} ⁿ k _i n _i + L-nh) (c ± v) ² p} / {hcΣ _{i = 1} ⁿ k _i (1 + n _i )}] cos β ₀ = hΣ ^{i = 1n} k ⁱ (1 + n ⁱ )-{(c ± v) (hΣ ^{i = 1n} k ⁱ n ⁱ + L-nh)} / c ∴ cosβ ₀ = [hΣ _{i = 1} ⁿ k _i (1 + n _i )-{(c ± v) (hΣ _{i = 1} ⁿ k _i n _i + L-nh)} / c] / [(c ± v) p-{(hΣ _{i = 1} ⁿ k _i n _i + L-nh) (c ± v) ² p} / {hcΣ _{i = 1} ⁿ k _i (1 + n _i )}] (15) In (15), c: propagation velocity of radio wave v: rotation velocity of earth p: propagation velocity of radio wave P → A h: parallel plane layer of atmospheric gas (including ionosphere) parallel to horizontal plane passing through receiver position The thickness is 1 km. k _i ; refractive index in the vicinity of the path of the radio wave P → A, k _i = {(1-sin ² α ₀ ) / (n _i ² -sin ² α ₀ )} ^1/2 n _i ; of the radio wave P → A Refractive index L in the vicinity of the path; cosβ ₀ is determined from the height from the xy-plane of the satellite, because it has already been determined. Therefore, β _{0 is} also determined. The rotation direction of the earth is assumed to be parallel to the y axis. Assuming that the angles formed by the straight lines AQ and BQ and the x-axis are γ and δ, respectively (see FIG. 2), [-hΣ _{i = 1} ⁿ tanα _i + {c (T _A -T _P ) -hΣ _{i = 1} ⁿ _{(1 / cosα i)} sinα} 0 ] cos = ^{_{[- hΣ i = 1 n tanβ i}} + {c (T B -T P) -hΣ i = 1 n (1 / cosβ i)} sinβ 0 ] cosδ [- ^{_{hΣ i = 1 n tanα i +}} {c (T A -T P) -hΣ i = 1 n (1 / cosα i)} sinα 0 ] _{sinγ + v (T B -T A} ) = [- hΣ _{i = 1} ⁿ tan β _i + {c (T _B -T _P ) -h Σ _{i = 1} ⁿ (1 / cos β _i )} sin β ₀ ] sin δ where α ⁱ and β ⁱ are the xy-plane passing through the receiver positions A and B Is the refraction angle of the radio wave passing through the parallel plane layer of the atmospheric gas layer (including the ionosphere) of thickness h (1 km) parallel to. ^{_{-hΣ i = 1 n tanα i +}} {c (T A -T P) -hΣ i = 1 n (1 / cosα i)} sinα 0
^{_{= A -hΣ i = i n tanβ}} i + {c (T B -T P) -hΣ i = 1 n (1 / cosβ i)} sinβ 0
= B v (T ^B -T ^A ) = C, A, B and C are determined. sinγ = (B ² -C ² -A ² ) / 2AC sinγ = (B ² -A ² + C ² ) / 2BC For details, see Japanese Patent Application No. 3-123205 (submitted March 4, 1991,
Submission of amendment Please refer to "6 azimuth measurement" of "3D position measurement by communication satellite" on August 20, 1991) Therefore, γ and δ are also determined. Thus x = AQcosγ = Acosγ y = AQsinγ = Asinγ z = nh + (cp-hΣ i = 1 n (1 / cosα i)) cosα 0, the position of the point P is determined.

◆ 3 A method of measuring the refractive index of the atmospheric gas layer (including the ionosphere) in the vicinity of the radio wave path connecting the satellite and the GPS receiver using the satellite whose position is fixed (measuring the elevation angle of the received radio wave) Method of determining the refractive index without. The position of the satellite at time T _P1 is P1. The radio wave radiated from the point P1 reaches the GPS receiver at time T _A1 , and the position of the GPS receiver at this time is A1. GP
From the radio wave from a certain satellite received by the S receiver, the emission time of this radio wave from that satellite can be known. However, since the GPS receiver receives the radio wave in which the position data corresponding to the time of the satellite is recorded from the geostationary satellite, the position data of the satellite at the time when this radio wave is emitted can be known. By receiving radio waves from each satellite whose position is known, GP
The approximate location of the S receiver is known. Letting the position of this GPS receiver be the origin, and the position coordinate of one of the satellites is (L _x , L _y , L _z ), L _z = nh + (cp-hΣ _{i = 1} ⁿ (1 / cosα _i )) cosα ₀ = nh + cp cosα ₀ -hΣ _{i = 1} ⁿ k _i n _i (16) cosα ₀ = hΣ _{i = 1} nk _i (1 + n _i ) / (c ± v) p (17) , P = T _A1 -T _P1 For details on the establishment of equations (16) and (17), see Japanese Patent Application No. 3-123205.
(Submission March 4, 1991, submission of amendment August 20, 1991
Japan, "Three-dimensional position measurement by communication satellite""3 Correction of satellite position error due to atmospheric refractive index", "4 Measurement of elevation angle"
See. From equation (17), cos α ₀ (c ± v) p = hΣ _{i = 1} ⁿ k _i (1 + n _i ) cp ・ cos α ₀ ± v p ・ cos α ₀ = hΣ _{i = 1} ⁿ k _i (1 + n _i ) cp ・ cos α ₀ = hΣ _{i = 1} ⁿ k _i (1 + n _i ) vp ・ cos α ₀ (18) Substituting equation (18) into equation (16), L _z = nh + hΣ _{i = 1} ⁿ k _i (1 + n _i ) vp ・ cosα ₀ -hΣ _{i = 1} ⁿ k _i n _i = nh + hΣ _{i = 1} ⁿ k _i + hΣ _{i = 1} ⁿ k _i n _i vp ・ cos α ₀ -hΣ _{i = 1} ⁿ k _i n _i = nh + hΣ _{i = 1} ⁿ k _i vp ・ cosα ₀ (19) Since hΣ ^{i = 1n} k ⁱ is approximately displayed as a function of cosα ₀ , from equation (19), cos α ₀ is obtained. For how to obtain hΣ _{i = 1} ⁿ k _i , see “◆ 7 How to obtain the refractive index of the atmospheric gas layer (including the ionosphere)”. Such operation 1
By repeating 000 times, 1000 pieces of cos α ⁱ and propagation time p _i can be obtained. From these, ◆ 1 The first-order approximation of the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path connecting the satellite and the measurement point can be obtained by the method of measuring the radio refractive index of the ionosphere and atmospheric gas layer. . Therefore, the horizontal distance and the vertical distance from the measurement point to the satellite can be obtained. Since the position of the satellite has been fixed, the position of the measurement point can be known. From the first-order approximation value of the refractive index, the second approximation value of cos α _i is found, and further the second approximation value of the refractive index is found, and gradually approaches the true value of the refractive index. The above process is repeated, and when the calculation converges with the required accuracy, the calculation is terminated.

◆ 4 A method for measuring the refractive index of the atmospheric gas layer (including the ionosphere) in the vicinity of the radio path connecting the satellite and the GPS receiver, using a satellite whose position is known. (A method to obtain the refractive index without measuring the elevation angle of the received radio waves.) Receive the radio waves from the four satellites in the sky and determine the approximate position where the GPS receiver is placed. Therefore, the approximate vertical distance between these satellites and this receiver is determined.
Also, when the position of the receiver on the ground is fixed, the vertical distance between this satellite and this receiver is known from the content of a navigation message received by this receiver. Now, as the origin the location of the GPS receiver, the vertical distance to one of the satellites in the sky and _{L z, L z = nh +} (cp-hΣ i = 1 n (1 / cosα i)) cosα 0 cosα ₀ = hΣ _{i = 1} ⁿ k _i (1 + n _i ) / (c ± v) p For details of the establishment of the above two equations, refer to Japanese Patent Application No. 3-123205 (submitted March 4, 1991, amendment Submission August 20, 1991 “3D position measurement by communication satellite” “3. Correction of satellite position error due to atmospheric refractive index”, “4 Measurement of elevation angle”) From the above two equations, L _z = nh ^{_{+ hΣ i = 1 n k i}} vpcosα 0 (20) hΣ i = 1 n k i , since being approximately as a function of cos [alpha] _0, the equation (20), cos [alpha] ₀ is obtained. For how to obtain hΣ _{i = 1} ⁿ k _i , see “◆ 7 How to obtain the refractive index of the atmospheric gas layer (including the ionosphere)”. Such operation 1
By repeating 000 times, 1000 pieces of cos α _i and propagation time p _i can be obtained. From these, ◆ 1 The first-order approximation of the refractive index of the atmospheric gas layer (including the ionosphere) near the radio path connecting the satellite and the measurement point can be obtained by the method of measuring the radio refractive index of the ionosphere and atmospheric gas layer. . From the first-order approximation value of the refractive index, the second approximation value of cos α _i is found, and further the second approximation value of the refractive index is found, and gradually approaches the true value of the refractive index. The above process is repeated, and when the required accuracy calculation converges, the calculation is terminated.

5 Correction of error of GPS receiver clock etc. The position of each satellite is (x _i , y _i , z _i ), and the position of the measurement point is (x ₀ , y ₀ ,).
z ₀ ), the linear distance between each satellite and the measurement point is r _i , and the distance the radio wave travels between errors of the GPS receiver clock is s, (x _i -x ₀ ) ² + (y _i -y ₀ ) ² + (z _i -z ₀ ) ² = (r _i + s) ^{2 The} unknown (x ₀ , y ₀ , z ₀ ) is represented by the sum of its approximate value and the correction amount, and the formula is corrected By expanding the value and assuming that the correction value is minute, omitting terms of the second and higher order and linearizing the equation,
It becomes a simultaneous equation for the correction values. The obtained correction value is added to the approximate value to make a solution for the time being. The unknown value is re-established and replaced with the sum of the solution just obtained and the new correction value, and the above process is repeated. When the calculation converges with the required accuracy, the calculation is terminated. As a result, the true position of the measurement point in which the error of the clock or the like of the GPS receiver is corrected can be obtained.

[6] Method of Measuring Arrival Time of Radio Wave to Receiver At 00:00 am GMT, the contents of the canters A and B are 0. The time measurement code generation circuit operates at midnight GMT and outputs a code signal of 1000 MBPS. Then, the number of bits of the output code signal is always counted, and the number of bits is stored in the canter B. Unless the receiver receives a signal from the outside, the contents of the canter B are counted in one second after one second elapses. After adding to the contents of, the contents of canter B are reset. Now, when this receiver receives the radio wave from the satellite, the contents of the canter B at this time are added to the contents of the canter A, and then the contents of the canter B are reset. The contents of the canter A at this time represent the arrival time of the radio wave from the satellite at this receiver. The time measurement code generation circuit continues to operate as it is. (See Figure 4)

◆ 7 Determination of Refractive Coefficient of Atmospheric Gas Layer (Including Ionosphere) "The circumference of the earth is divided into an atmospheric gas layer (including ionosphere) and a radio wave rectilinear layer, and the area 1000 km above the ground surface is the atmosphere. The gas layer (including the ionosphere) is used, and the region higher than that is used as the radio wave rectilinear layer. Atmospheric gas layer (including ionosphere)
It is divided into parallel plane layers of thickness h (1 km) parallel to the horizontal plane passing through the point where the radio wave receiver is located on the ground surface, and the radio wave refraction index of each parallel plane layer is n _j and the radio wave refraction coefficient is k _ij . To do. or,
_Letting α _{i0 be} the incident angle of the radio waves emitted from the satellite at the interface between the radio wave rectilinear layer and the atmospheric gas layer (including the ionosphere), k _ij = {(1-sin ² α _i0 ) / (n _j- The relationship sin ² α _i0 )} ^1/2 holds. Now, with n _j on the horizontal axis and k _ij on the vertical axis, and α _i0 as a parameter, as shown in FIG. 5, k _ij = f (cosα _i0 ) n _j ² + g (cosα _i0 ) n _j + h (cosα _i0 ) Note that f (cosα _i0 ), g (cosα _i0 ), and h (cosα _i0 ) are approximated by a parabola having cosα _i0 as a variable. Therefore, hΣ _{i, j = 1} ⁿ k _ij = h {f (cosα _i0 ) Σ _{j = 1} ⁿ n _j ² + g (cosα _i0 ) Σ _{i = j}
It is represented by ⁿ n _j + hΣ _{i = 1} ⁿ 1}, and Σ _{j = 1} ⁿ n _j is fixed, so hΣ _{i, j = 1} ⁿ k
_ij is obtained as a function of cosα _i0 .

[Brief Description of Drawings] (1)

[Fig. 1] Explanation The circumference of the earth is divided into atmospheric gas layer, ionosphere and radio wave rectilinear layer. The atmospheric gas layer and the ionosphere are not treated individually, but are collectively referred to as the atmospheric gas layer (including the ionosphere). Atmospheric gas layer (including ionosphere) is 10 from the ground surface
The area up to 00 km is set, and the area higher than this is set as the radio wave straight traveling layer. The atmospheric gas layer (including the ionosphere) is divided into parallel plane layers of thickness h (1 km) parallel to the horizontal plane passing through the receiver on the ground surface. At time T _Pi , the radio wave radiated from the satellite position Pi to the receiver on the ground surface propagates, and at time T _Ai , the radio wave propagation state when reaching the receiver position Ai is shown. . (2)

Description of FIG. 2 Let the position of the satellite at time T _{P be} P, and its coordinates be P
(X, Y, Z). Times at which the radio waves radiated from the satellite position P at time T _P reach the receiver on the ground surface are T _A and T _B, and the positions of the receiver at this time are A and B, respectively. Let Q be a foot of a perpendicular line drawn from the point P to the xy-plane. (However, the receivers at the points A and B are the same.) The state of radio wave propagation in the vicinity of the radio wave path connecting the satellite and the receiver at this time is shown. (3)

Description of FIG. 3 Considering that the radio wave from the GPS satellite is a pulse signal consisting of 1 bit to several bits, each pulse signal is numbered 1,
2 shows the waveform of the C / A code when i is set. (4)

FIG. 4 is a conceptual diagram showing a method for measuring the arrival time of a radio wave at a receiver. The figure at the bottom of the page is a schematic circuit diagram showing the method. (5)

FIG. 5 shows the relationship between the refractive index and the refractive index of each parallel plane layer of the atmospheric gas layer (including the ionosphere).

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

Claims (4)

[Claims] 1. A radio wave from a GPS satellite is considered as a pulse signal composed of one bit to several bits, and the time when each pulse signal reaches a receiver on the ground is measured. If the reception time of the leading pulse signal is accurately measured, the reception times of other pulse signals are naturally determined. In this way, the arrival time of pulse signals from 1000 or more satellites to the terrestrial receiver is measured within 1 ms to several ms. Also, the elevation angle of each pulse signal when it reaches the receiver antenna is measured. If the elevation angle of the leading pulse signal is measured accurately, the elevation angles of other pulse signals can be measured naturally. In this way, the ionosphere and atmospheric gas layer are divided into parallel plane layers of thickness h (1 km) parallel to the horizontal plane passing through the receiver on the ground surface, and each parallel plane near the radio path connecting the satellite and the receiver. Plane ionosphere
Obtain the refractive index of the radio wave that passes through the atmospheric gas layer by the method of ◆ (1). 2. A GPS receiver is placed at a position where the latitude, longitude and height are fixed, and radio waves from each satellite are received every 15 seconds. Next, the reception time at the ground receiver at the beginning of the pulse signal indicating the Z cant at the beginning of each subframe of the navigation message is measured, and the propagation time of the radio wave radiated to the receiver at the time indicated by the Z cant is measured. To measure. The propagation time of the radio wave radiated from the satellite to the receiver at the time indicated by Z cant is T ₁ when the head of the pulse signal waveform reaching the receiver reaches the receiver. And Letting u be the number of bits from the first bit of the pulse signal waveform that reaches the receiver to the time when the first bit of the Z cant at the beginning of each subframe is first read, then T ₁ −u × 10 ⁻⁶ . With this, the position of each satellite at a certain time is determined by the method of (2). In this way, the positions of satellites at certain fixed time intervals are determined, and the position data of these time-corresponding satellites are transmitted to the whole country via the geostationary satellite located at a position 36000 km above the equator. 3. Each surveyor places a GPS receiver at the measurement point. Radio waves (C / A code) from GPS satellites are considered as pulse signals consisting of 1 bit to several bits, and the reception time of each pulse at the GPS receiver is measured, and the ionosphere and atmospheric gas layer are on the ground surface. It is divided into parallel plane layers of thickness h (1 km) parallel to the horizontal plane passing through the receiver, and the ionosphere of each parallel plane layer near the radio path connecting the measurement point and each satellite, the refractive index of the radio wave of atmospheric gas is ◆ ( 3) and ◆ Use the method of (1).
As a result, the horizontal distance and vertical distance from the measurement point to each satellite can be obtained. However, since the position of each satellite is transmitted nationwide via the geostationary satellite, it can be known by receiving this data, so the position of the measurement point can be obtained. However, the position of the measurement point thus obtained is G
Due to the error of the PS receiver clock, etc., it does not match ◆
Correct by the method of (4). 4. Each surveyor places a GPS receiver at the measurement point. Radio waves from four satellites in the sky are received by this GPS receiver to obtain the approximate position of this measurement point. For one of the satellites, the position of the satellite can be known from the navigation message, so the vertical distance and horizontal distance from this measurement point as the origin are obtained. From this, ◆
By the method of 4, the incident angle of the radio wave on the interface between the radio wave straight traveling layer and the atmospheric gas layer (including the ionosphere) is obtained. By repeating this operation 1000 times, the first-order approximation value of the refractive index of the atmospheric gas layer (including the ionosphere) is obtained. Therefore, by repeating the above operation several times, the refractive index of the atmospheric gas layer (including the ionosphere) that is infinitely close to the true value of the refractive index of the atmospheric gas layer (including the ionosphere) is obtained. In addition, the circumference of the earth is divided into an atmospheric gas layer, an ionosphere, and a radio wave straight-ahead layer, and a space of 1000 km or more from the ground surface is called a radio wave straight-ahead layer.