JP2001051041A - Selection system for kinematic gps satellite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new selection system for a main satellite which can provide a stable kinematic GPS positioning solution. SOLUTION: In the case of a GPS satellite, the influence of a multipath is smaller the larger its angle of elevation is. When a GPS satellite whose angle of elevation is largest out of receiving GPS satellites is selected as a main satellite, the influence of a multipath can be reduced (Step A3). In addition, the discontinuity of a positioning point due to a change in the direction of the main satellite is eliminated by a positioning filter (Step A5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a kinematic G
The present invention relates to a PS satellite selection method, and more particularly to a main satellite selection method for providing a stable kinematic GPS (KGPS) positioning solution, and more particularly to a fixed-station GPS receiver whose coordinates are set at known points. And a mobile station GPS using a mobile station GPS receiver set at an unknown point.
The present invention relates to kinematic positioning for performing positioning by sequentially moving a receiver to a measurement target point.

[0002] GPS (Global Position)
ing System (GPS positioning system) is a system that measures the position of a user by using a plurality of satellites and a control station on the ground, and determines the position of the user by the difference between the arrival times of radio waves from four or more satellites. Measuring.

[0003] Kinematic GPS is executed by fixing one GPS receiver at a known point of coordinates and sequentially moving the other GPS receiver to an unknown point (measurement target point).

[0004]

2. Description of the Related Art As a first example of a conventional KGPS positioning method, there is a technique disclosed in Japanese Patent Application Laid-Open No. 9-311180.

The first conventional example uses a GPS receiver for a fixed station installed at a location where coordinates are known and a GPS receiver for a mobile station installed at an unknown location and uses the GPS for a fixed station. A kinematic survey in which the antenna of the mobile station GPS receiver is installed immediately below the antenna of the receiver, the measurement for obtaining the initial ambiguity solution is performed, and then the mobile station GPS receiver is moved. Calculating means for calculating a horizontal angle and an altitude angle of a received radio wave from almanac data of GPS satellites stored in advance or a satellite currently being received, and Display means for displaying the azimuth angles of a plurality of radio waves incident on the antenna. A GPS receiver for kinematic positioning.

In the first conventional KGPS positioning method, there is no KGPS satellite selecting means. Such a conventional KGPS positioning method operates as follows.

That is, there is a possibility that all the satellites among the captured satellites are selected as the main satellites.

As a second conventional example, Japanese Patent Application Laid-Open No. H10-253
No. 739 is disclosed.

In the second conventional example, in a GPS receiver that receives radio waves transmitted from a plurality of artificial satellites and measures the reception position, the order is given to the order of receivable elevation angles. From the initial 4 satellites, and the DOP (Dilution of
Precision “Rate of decrease in accuracy in performing positioning”) is calculated, and the calculated DOP value and a preset D
The calculated DOP is compared with the OP limit value, and if the calculated value is smaller than the DOP limit value, the satellite combination is determined.
If the value is larger than the DOP limit value, +1 satellites are selected in order from the larger elevation angle, and all DOP values obtained by the combination of the +1 satellites are calculated.
The minimum value of the calculated DOP value is obtained, and the minimum value and DO are calculated.
The minimum value is compared with the P limit value, and if the minimum value is smaller than the DOP limit value, a combination of satellites giving the minimum value is determined.
If the minimum value is larger than the DOP limit value, the satellites are selected again by the number of +1 from the larger elevation order, and the DOP is calculated for all the combinations of the selected satellites. The minimum value of the calculated DOP value , And this minimum value and DOP
A GPS receiver which repeatedly determines the combination of satellites that gives a state in which the DOP value is smaller than the DOP limit value by giving priority to the combination of satellites in the higher elevation order by repeatedly comparing with the limit value. This is a method for determining the combination of satellites.

[0010]

However, the above-mentioned prior art has the following problems.

That is, the problem of the first conventional example is that since the selection of the main satellite is free, there is a possibility that a satellite which is greatly affected by multipath may be selected.

The second conventional example described above is not for improving accuracy for KGPS but for obtaining a stable solution in DGPS. Four satellites are selected in descending order of elevation and positioning is performed. (Japanese Patent Laid-Open No. 10-253)
If the number of satellites is limited to four, the accuracy of the positioning solution may be degraded in the case of KGPS processing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and has been made to solve the above-mentioned drawbacks inherent in the conventional technology. Therefore, an object of the present invention is to provide a stable KGPS positioning solution. Another object of the present invention is to provide a new method for selecting a main satellite that has made possible.

[0014]

In order to achieve the above object, a kinematic GPS satellite selection system according to the present invention is a system using a GPS system, wherein one GPS receiver is located at a known point of coordinates. Fixed to base station GP
An S receiver, the other GPS receiver is arranged at a measurement target point, and a mobile station GPS receiver is used. The mobile station GPS receiver is sequentially moved to a positioning target point to execute positioning and select a GPS satellite. Kinematic GPS
The satellite selection method is characterized in that the GPS satellite having the highest elevation angle is selected as the main satellite from the selected GPS satellites.

A first step of calculating an initial position of a position and a speed of the mobile station GPS receiver as a process of selecting the GPS satellite having the highest elevation angle as a main satellite;
A second step of creating a search cube using the data used for the position, velocity, and estimation; and a third step of calculating an elevation angle of each GPS satellite from the GPS data and selecting a satellite having the largest elevation angle as a main satellite. Steps and then KGPS
And performing a positioning calculation to obtain a positioning solution.

The present invention also has a fifth step of inserting a filter so that the solution does not become discontinuous when the main satellite is selected in the third step.

In the present invention, the reference station GPS
A main satellite is selected between a receiving device and the mobile station GPS receiving device by using the GPS data obtained by the reference station GPS receiving device and the GPS data obtained by the mobile station GPS receiving device to select another satellite. And a data processing device which performs positioning using the double phase difference and operates under program control.

[0018]

Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a KGPS positioning system to which the present invention is applied, and FIG. 2 is a block diagram showing an embodiment according to the present invention.

[Configuration of Embodiment] In FIG. 1, a GPS satellite 101 or 1 having a low elevation angle as viewed from a positioning point 110 is shown.
When 05 is selected as the main satellite, a satellite having a low elevation angle is susceptible to the influence of multipath and shielding, and the received signal is not stable. On the other hand, the GPS satellite 103 having a high elevation angle is less affected by multipath, and is not affected by shielding or the like. Therefore, the GPS satellite having the highest elevation angle is selected as the main satellite. However, when changing the selection of the main satellite,
By inserting a filter in the positioning, discontinuity of the solution is prevented. Thus, according to the present invention, a stable KGPS
Enable to obtain positioning solution.

Referring to FIG. 2, a KGPS according to the present invention is shown.
One embodiment of the satellite selection system includes a data processing device 200 that operates under program control, a reference station GPS receiving device 210 and a mobile station GPS receiving device 220, GPS data transmitting devices 230 and 240, and a GPS satellite group 250.
It is composed of

The data processing device 200 includes a KGPS satellite selecting means 201 and a KGPS positioning means 202.

The reference station GPS receiver 210 includes a GPS receiver 211 and a GPS data generator 212.

The mobile station GPS receiver 220 includes a GPS receiver 221 and a GPS data generator 222.

The GPS data transmission device 230 includes a GPS data receiving means 231.

The GPS data transmission device 240 includes GPS data transmission means 241.

Each of these means operates roughly as follows.

The KGPS satellite selecting means 201 of the data processing device 200 transmits the GPS data obtained by the GPS data receiving device 231 of the GPS data transmitting device 230 to the reference station G.
Using the GPS data obtained by the GPS data generating means 212 of the PS receiving apparatus 210, a main satellite is selected and a double phase difference with another satellite is calculated. The double phase difference refers to an operation of measuring the phases obtained from two satellites at two points and taking the respective differences. That is, in the case of the satellites 1 and 2 and the positioning points A and B, the phases of the satellite 1 obtained at the positioning points A and B are P _A1 ,
P _B1 and the phases of satellite 2 obtained at positioning points A and B are denoted by P _A2 and P
_{Assuming B2} , (P _A1 −P _B1 ) − (P _A2 −P _B2 ) is a double phase difference. By performing the double phase difference, a common error caused by the satellite and the positioning point is deleted. Assuming that the main satellite is the satellite 1, it is necessary to calculate a double phase difference with the other satellites 2 to n (slave satellites).

The KGPS positioning means 202 of the data processing device 200 obtains the 2
Positioning is performed using the heavy phase difference.

The GPS receiving means 211 of the reference station GPS receiving apparatus 210 and the GPS receiving means 221 of the mobile station GPS receiving apparatus 220 receive the GPS signals transmitted from the GPS satellite group 250.

The GPS data generator 212 of the reference station GPS receiver 210 and the G of the mobile station GPS receiver 220
The PS data generation unit 222 converts the GPS signals such as ephemeris (broadcasting calendar), pseudorange, phase, etc. necessary for positioning from GPS signals.
Generate S data.

The GPS data receiving means 231 of the GPS data transmitting device 230
The GPS data transmitted by the PS data transmission means 241 is received.

The GPS data transmission means 241 of the GPS data transmission device 240
The GPS data generated by the PS data generator 222 is transmitted.

[Operation of the Embodiment] Next, the operation of the embodiment according to the present invention will be described in detail with reference to the flowchart of FIG. 3 and FIG.

First, the initial position of the position and speed of the mobile station GPS receiver 220 is calculated (step A in FIG. 3).
1).

Next, a search cube is created using the position, speed and data used for estimation (step A).
2). In KGPS positioning, since only the phase is used as the pseudorange for positioning, information on the phase of the wave cannot be obtained. It is necessary to determine a search range in the initial state in order to estimate it.

Further, the elevation angle of each GPS satellite is calculated from the GPS data, and the satellite having the largest elevation angle is selected as the main satellite (step A3).

Finally, a KGPS positioning calculation is performed to obtain a positioning solution (step A4).

Note that a filter is inserted so that the solution does not become discontinuous when the main satellite is selected in step A3 (step A5).

Next, a specific example will be described.

As shown in FIG. 4, the satellite positions x, y, z
Is calculated. This coordinate system is a Cartesian coordinate system centered on the receiving position, the zenith direction is the z axis, and the north direction is y
The direction orthogonal to the axis, z, and y axes is defined as the x axis.

The elevation angle is given by the following: arcsin (z / (x * x + y)
* Y + z * z) ^-0.5 ), the result of the calculation indicates that the elevation angle of the satellite 1 is the largest, and therefore the satellite 1 is selected as the main satellite.

By selecting the main satellite for each positioning calculation, the satellite with the largest elevation angle can always be selected as the main satellite.

[0044]

The present invention is constructed and operates as described above. According to the present invention, the following effects can be obtained.

The first effect is that a stable KGPS positioning solution can be obtained.

The reason is that by using a satellite with a high elevation angle as a main satellite, errors such as multipath can be reduced.

Only the common error can be removed by the above-described double phase difference, and an error that depends on the satellite position, the observation position, and the observation environment like a multipath is not eliminated. Although the dual phase difference is calculated from the GPS data of the master and slave satellites, the present invention is intended to minimize errors of the master satellite.

FIG. 5 shows a change in the influence of multipath due to the elevation angle of the satellite.

Referring to FIG. 5, the vertical axis indicates the parameters for evaluating the multipath, ie, the elevation angle of the satellite and the CC difference, and the horizontal axis indicates the time.
This is a graph from when the satellite (satellite number 1) ascends to when it sinks. It was measured without any obstacles around, and is not affected by shielding.

The larger the variance of the CC difference is, the larger the effect of the multipath is. As can be seen from FIG. 5, the smaller the elevation angle of the satellite is, the larger the variance is and the larger the effect of the multipath is. I have. Although the values in the figure are dominated by the multipath of the code, the qualitative change of the multipath is the same for the multipath of the phase. Therefore, selecting a satellite with a high elevation angle results in a stable positioning solution.

The CC difference (CCDIF) is a pseudo distance PR _code by _code and a pseudo distance PR by phase.
It is calculated by the following formula from _phase .

CCDIF = PR _code- PR _phase = ME
AS _code −MEAS _phase + c (21 + M _code −M _phase )
−Δ PR _code = R + c ( _bu− B) + c (T + I + M _code +
HW) + URE + SA + MEAS code PR phase = R + c (b u -B) + c (T-I + M
_phase + HW) + URE + SA + MEAS _phase + Δ c: speed of light, b _u : clock error of receiver, B: clock error of satellite,
T: atmospheric delay error, I: ionospheric delay error, M: multipath error, HW: delay error in receiver, R: calculation distance, S
A: SA error, MEAS: measurement error, Δ: ambiguity, URE: satellite position error, R: calculation distance Measurement error, ionospheric delay error, multipath error, ambiguity remains, but dispersion is as follows For this reason, it can be said that only the influence of the multipath is present.

The ambiguity is also called an integer value bias, and does not affect the dispersion because it is an offset value. The ionospheric delay error can be removed by correcting with a separately estimated value. The values in the figure have also been corrected. The measurement error is much smaller than the multipath error and can be ignored.

Further, by using a satellite having a high elevation angle as a main satellite, the influence of C / N deterioration during snowfall can be reduced. The C / N is reduced due to snowfall on the receiving antenna, and a satellite having a low C / N and a low elevation angle cannot obtain stable reception.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a KGPS positioning system to which the present invention is applied.

FIG. 2 is a block diagram showing an embodiment according to the present invention.

FIG. 3 is an operation flowchart showing one embodiment of the present invention.

FIG. 4 is a diagram showing calculation results of positions x, y, z, and elevation angles of satellites according to the present invention.

FIG. 5 is a diagram showing a change in the influence of multipath due to the elevation angle of the satellite.

[Explanation of symbols]

 101 to 105: GPS satellites 110: Positioning points 200: Data processing device 201: KGPS satellite selection means 202: KGPS positioning means 210: Reference station GPS receiver 211: GPS receiver 212: GPS data generator 220: Mobile station GPS receiver 221 GPS receiving means 222 GPS data generating means 230 GPS data transmitting apparatus 231 GPS data receiving means 240 GPS data transmitting apparatus 241 GPS data transmitting means 250 GPS satellite group

Claims (4)

[Claims] 1. A system using a GPS system, wherein one GPS receiver is fixed at a known point of coordinates to be a base station GPS receiver, and the other GPS receiver is arranged at a point to be measured and moved. In a kinematic GPS satellite selection system for performing positioning and selecting a GPS satellite by sequentially moving the mobile station GPS receiver to a positioning target point as a station GPS receiver, the most elevation angle of the selected GPS satellites A kinematic GPS satellite selection method characterized by selecting a GPS satellite with a high satellite speed as a main satellite. 2. A first step of calculating an initial position and a position of the mobile station GPS receiver as a process of selecting the GPS satellite having the highest elevation angle as a main satellite, and the position, speed and estimation. A second step of creating a search cube using the data used for the above, a third step of calculating the elevation angle of each GPS satellite from the GPS data and selecting the satellite with the largest elevation angle as the main satellite, and KG
A kinematic GPS satellite selection method according to claim 1, further comprising: a fourth step of performing a PS positioning calculation to obtain a positioning solution. 3. The method according to claim 2, further comprising a fifth step of inserting a filter so that the solution does not become discontinuous when the main satellite is selected in the third step. 2. The kinematic GPS satellite selection method according to 2. 4. Between the reference station GPS receiving apparatus and the mobile station GPS receiving apparatus, a main data is obtained by using GPS data obtained by the reference station GPS receiving apparatus and GPS data obtained by the mobile station GPS receiving apparatus. The data processing apparatus further comprising: selecting a satellite, calculating a double phase difference with another satellite, performing positioning using the double phase difference, and operating under program control. 2. The kinematic GPS satellite selection method according to 1.