JP3045931B2 - Differential GPS device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a global positioning system (GPS).
The present invention relates to a differential GPS device (D-GPS device) for locating a position with high accuracy.

[0002]

2. Description of the Related Art The configuration of a conventional differential GPS device will be described with reference to FIG. FIG.
Is, for example, the GPS International Symposium '93 "RTCM
FIG. 11 is a block diagram showing a configuration of a conventional differential GPS device (base station) shown on page 4 of “SC-104 Standard”.

In FIG. 11, reference numeral 1 denotes a GPS antenna, and 2 denotes a G including a high-speed operation unit, a CPU for controlling the operation unit, and a clock.
The PS receiver 3 is an input device such as a keyboard for inputting a known position of the base station. The reference numeral 4 is a CPU and the like. The distance between each GPS artificial satellite and the base station is obtained by the GPS receiver 2 and the input device. The processing unit obtains a difference from the distance calculated based on the position input from No. 3, that is, calculates a correction value of the pseudo distance.

Next, the conventional differential GPS
The operation of the device will be described. By GPS Antenna 1
The satellite information and the like transmitted from each satellite are received. Based on the received information, the GPS receiver 2 calculates axial road information and the like. Further, a radio wave propagation delay time from the satellite is calculated based on an accurate clock in the GPS receiver 2. The method of calculating the radio wave propagation delay time and the like are described, for example, in "GPS: Precise positioning system using artificial satellites", published by The Geodetic Society of Japan and published in November 1989 by the Japan Surveying Association.

[0005] This radio wave propagation delay time is measured by a measured value T _A1 (# 1
To the processor 4). In addition, the processor 4 receives from the input device 3 position information in which the position of the base station is known in advance. The radio wave propagation delay time predicted from this position information is obtained as a calculated value T _B1 .

Next, the processor 4 obtains a difference ΔT ₁ between the measured value T _A1 and the calculated value T _B1, and multiplies the value of the speed of light C [km / sec] ΔD ₁ = ΔT ₁ -Let C be the pseudo distance correction value for artificial satellite # 1. In a series of these processes, pseudo distance correction values are obtained for all visible satellites from the base station. For example,
When there are five visible satellites, the pseudo distance correction values ΔD ₁ , ΔD ₂ ,
ΔD ₃ , ΔD ₄ , and ΔD ₅ are obtained, and notification is made to the user terminal.

[0007]

The conventional differential GPS device as described above has a problem that if the accuracy of the position of the known base station is poor, the error of the pseudo distance correction value increases.

Further, when the user's terminal side obtains its own position using the pseudo distance correction value, it uses three or four satellites, but the position shifts when the combination of the satellites changes. was there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide a differential GPS device capable of obtaining a pseudo distance correction value with higher accuracy.

Another object of the present invention is to provide a differential GPS device capable of minimizing a positional shift due to a combination of satellites.

[0011]

According to a first aspect of the present invention, there is provided a differential GPS device comprising: a pseudo-D-GPS;
A base station for calculating a distance correction value and notifying the user terminal,
Separated by a predetermined distance from the base station to measure the exact distance
And an auxiliary station provided at a location where the auxiliary station is located.
The second G receiving the satellite information transmitted from the artificial satellite
A PS antenna and the satellite based on the satellite information.
Calculate the second actually measured value of the radio wave propagation delay time with the auxiliary station
A second GPS receiver, wherein the base station comprises
First GP for receiving satellite information transmitted from a satellite
S antenna and the satellite based on the satellite information.
Calculating the first measured value of the radio wave propagation delay time with the base station;
1 GPS receiver and measured by means other than GPS
Location information of the base station and between the base station and the auxiliary station
An input device for inputting relative position information of the base station;
Radio wave propagation delay between the satellite and the base station based on the location information.
Calculating a first calculated value of the delay time, and
Location information and the relative position between the base station and the auxiliary station
Radio wave propagation delay between the satellite and the auxiliary station based on the information
Calculating a second calculated value of time, the first measured value and the second measured value;
A first difference between a first calculated value and the second actually measured value and the second
Calculating a second difference between the two calculated values, and calculating the first and second differences.
Are equal to each other, the pseudo distance correction value is calculated based on the first difference.
Is calculated, and when the first and second differences are different, the
Position the base station on the line connecting the satellite and the base station.
Position the auxiliary station parallel to the line connecting the satellite and the base station.
And the first and second differences are equal on a line passing through the auxiliary station.
Are shifted based on the first difference.
And a processor for calculating a distance correction value .

According to a second aspect of the present invention, there is provided a differential GPS device, comprising: a line connecting the base station and the auxiliary station;
A right-angled intersection and located on a line passing through the base station
Two auxiliary stations, wherein the second auxiliary station is the person
3rd G receiving satellite information transmitted from engineering satellite
A PS antenna and the satellite based on the satellite information.
Calculate the third measured value of the radio wave propagation delay time with the second auxiliary station
And a third GPS receiver for transmitting the data.
Device is based on the location information of the base station and the input device.
The base station measured by means other than the input GPS
On the basis of relative position information between the
The third radio propagation delay time between the satellite and the second auxiliary station
Calculating a calculated value, the third actually measured value and the third calculated value
Is calculated, and the base station, the auxiliary station, and the second complement are calculated.
The location of the auxiliary station is included by the base station, the auxiliary station and the second auxiliary station.
The first, second and third differences on the surface to be inserted are minimized
The pseudo distance compensation is performed based on the first difference.
A positive value is calculated .

[0013]

In the differential GPS device according to the first aspect of the present invention, the pseudo distance correction value of D-GPS is
A base station that calculates and notifies the user terminal;
At a predetermined distance that allows accurate distance measurement
An auxiliary station, which is transmitted from an artificial satellite.
Second GPS antenna receiving satellite information being transmitted
Between the artificial satellite and an auxiliary station based on the satellite information.
Second GP for calculating a second actually measured value of radio wave propagation delay time
S receiver, and the base station transmits from the artificial satellite.
First GPS antenna receiving satellite information being transmitted
Between the artificial satellite and the base station based on the satellite information.
A first GP for calculating a first actually measured value of the radio wave propagation delay time
S receiver and the base measured by means other than GPS
Station location information and the relative position between the base station and the auxiliary station
An input device for inputting location information;
Of the radio wave propagation delay time between the artificial satellite and the base station based on
Calculating a first calculated value, and calculating a position information of the base station;
Information and relative position information between the base station and the auxiliary station.
Of the radio wave propagation delay time between the satellite and the auxiliary station
2 is calculated, and the first measured value and the first total value are calculated.
A first difference between calculated values, the second actually measured value, and the second calculation
Calculating a second difference between the values, wherein the first and second differences are equal
In the case, a pseudo distance correction value is calculated based on the first difference.
And when the first and second differences are different, the base station
On the line connecting the satellite and the base station,
Position the station parallel to the line connecting the satellite and the base station;
The first and second differences are equal on a line passing through the auxiliary station
The pseudo distance compensation is performed based on the first difference.
Because it has a processor for calculating a positive value, pseudorange correction value
Can be obtained with high accuracy .

In a differential GPS device according to a second aspect of the present invention, the base station and the auxiliary station are connected to each other.
Located on a line that crosses the connecting line at right angles and passes through the base station
A second auxiliary station, further comprising:
Receives satellite information transmitted from the artificial satellite.
Based on the third GPS antenna and the satellite information.
The third radio propagation delay time between the satellite and the second auxiliary station
A third GPS receiver for calculating an actual measurement value,
The processor of the local station is configured to store the location information of the base station and the input device.
Measured by means other than GPS input by
Based on relative position information between the base station and the second auxiliary station.
The radio wave propagation delay between the satellite and the second auxiliary station
Calculating a third calculated value between the third measured value and the third calculated value.
3 to calculate the third difference between the base station, the auxiliary station,
And the positions of the second auxiliary station and the base station, the auxiliary station and the second auxiliary station.
The first, second and third differences on the plane where the auxiliary station is included
Based on the first difference.
Since the pseudo distance correction value is calculated , the pseudo distance correction value
It can be obtained with high accuracy .

[0015]

【Example】

Embodiment 1 FIG. Hereinafter, a configuration of an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.
The PS receiver 2 and the input device 3 are the same as those of the conventional device. In the drawings, the same reference numerals indicate the same or corresponding parts.

In FIG. 1, reference numeral 4A denotes a processor including a CPU and the like, 5 denotes a GPS antenna, 6 denotes a high-speed operation unit, a CPU for controlling the operation unit, and a GPS receiver including a high-precision clock. The base station 7 includes the GPS antenna 1 to the processor 4A, and the auxiliary station 8 includes the GPS antenna 5 and the GPS receiver 6. Further, the auxiliary station 8 is provided at a position where an accurate distance can be measured from the base station 7, for example, at a position separated by about 100 m.

Next, the operation of the first embodiment will be described with reference to FIG.
This will be described with reference to FIG. FIG. 2 is a diagram for explaining the operation of the first embodiment of the present invention. FIG.
5 is a flowchart showing the operation of the first embodiment of the present invention.

As in the operation of the conventional device, the G
G based on the satellite information received by the PS antenna 1
The PS receiver 2 calculates the actual measured value T _AN of the radio wave propagation delay time between the satellite 9 of ♯N and the base station 7 and sends it to the processor 4A. Similarly, the auxiliary station 8 sets the GPS receiver 6 based on the satellite information and the like received by the GPS antenna 5,
Of the radio wave propagation delay time between the satellite 9 and the auxiliary station 8
_An is calculated and sent to the processor 4A.

On the other hand, the processor 4A inputs the position of the base station 7 and the highly accurate relative positional relationship between the base station 7 and the auxiliary station 8 from the input device 3. The processor 4A calculates the calculated values of the radio wave propagation delay times of the base station 7 and the auxiliary station 8 based on the known position information, and _sets them as T _BN and T ′ _BN .

The processor 4A calculates the difference (T _AN −T _BN ) between the measured value and the calculated value of the delay time of the base station 7 and the difference (T ′ _AN −) between the measured value and the calculated value of the delay time of the auxiliary station 8. If _T'BN ) is equal, a pseudo distance correction value is calculated based on these differences.

If not equal, the processor 4A performs processing so as to minimize the error. Hereinafter, this processing method will be described with reference to FIG. In FIG.
The positions of the satellite 9, the base station 7 and the auxiliary station 8 are denoted by C,
A and B.

When the difference between the measured value and the calculated value of the delay time between the base station 7 and the auxiliary station 8 is different, the known position of the base station 7 is slightly shifted on the line between the satellite 9 and the base station 7 (on the CA). Also supplement
The position of the assistant station 8 is indicated by a line passing through B and parallel to the line CA (shown by a dotted line).
) So that the difference between the two delay times is the same. At that time, the positional relationship between A and B with very high precision is preserved. Then, for example, the their these positions A 'and B' to the base station 7 及 it for satellite 9
And the position of the auxiliary station 8 . By performing these processes, the position of each base station 7 is corrected for all visible satellites, and a pseudo distance correction value is obtained. Therefore, a pseudo distance correction value can be obtained with high accuracy.

Hereinafter, the operation will be described with reference to the flowchart of FIG. In step 30, the base station 7 and the auxiliary station 8 are arranged. Next, in step 31, the position of the base station 7 is accurately measured by positioning means other than GPS,
The relative position with respect to the auxiliary station 8 is also accurately measured.

In step 32, the base station 7 and the auxiliary station 8 determine their own positions (actually measured values) using the respective GPS receivers 2 and 6. Next, in step 33, a difference (pseudo-distance correction value) between the distance between each station and the satellite is calculated from the position accurately measured at each station and the GPS position.

In step 34, a new correction value is calculated by the algorithm of FIG. 2 based on the pseudo distance correction value of the base station 7 and the pseudo distance correction value of the auxiliary station 8. Next, in step 35, it is determined whether or not the same processing has been performed for all satellites. When all processing is completed, in step 36, a new correction value is notified to the D-GPS user. In step 35, when there are a plurality of auxiliary stations as in the other embodiments described below, it is determined whether the same processing is performed for each auxiliary station.

Embodiment 2 FIG. Second Embodiment A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the second embodiment of the present invention.

In FIG. 4, one auxiliary station is provided in the first embodiment, but two auxiliary stations are provided in the second embodiment. These auxiliary stations 8, 12 are arranged at right angles as much as possible.

When the number of auxiliary stations is one, only the position of the base station 7 can be corrected on the line. However, when the number of auxiliary stations is two, correction can be made for two-dimensional degrees of freedom. A highly accurate pseudo distance correction value can be obtained.

Hereinafter, the correction processing method will be described with reference to FIG. As shown in FIG. 5, since there is a two-dimensional degree of freedom, the error of the correction value of the base station 7, the auxiliary station 1 (8), and the auxiliary station 2 (12) on the plane having the point ABD Is the minimum , that is, the delay time of the above three stations
There seems to be no case where the difference between the measured value and the calculated value is the same
The difference between the measured and calculated delay times of the three stations is minimized.
So as to shift the position of the three stations on said surface, it et al. A ', B', when the D ', which it pseudo base station for the satellite 9, the auxiliary station 1, the point of the auxiliary station 2. This correction method is optimal when the user terminal performs two-dimensional positioning.

Embodiment 3 FIG. Third Embodiment A third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a diagram for explaining the operation of the third embodiment of the present invention. As shown in FIG. 6, a third auxiliary station may be provided at a point E just above the base station 7.

When the user terminal performs three-dimensional positioning, one additional auxiliary station is added, the three stations have three-dimensional degrees of freedom, and the position of the base station 7 is corrected. Can be minimized. Therefore, the position error of the user terminal is smaller than that of the conventional D-GPS device.

Embodiment 4 FIG. Embodiment 4 Embodiment 4 of the present invention will be described with reference to FIG. FIG. 7 is a block diagram showing a configuration of the fourth embodiment of the present invention.

In FIG. 7, reference numeral 13 denotes a high precision clock connected to the GPS receiver 2A of the base station, the processor 4C, and the GPS receiver 6A of the auxiliary station.

In the first to third embodiments, the precision of the clock is processed by using the internal clock of the GPS receiver of each station. In the fourth embodiment, the precision is distributed to each station by using the common high precision clock 13. Then, a pseudo-distance correction value is calculated by using it. The processing method is the same as in the first to third embodiments. Therefore, the position error of the user terminal is smaller than that of the conventional D-GPS device.

Embodiment 5 FIG. A fifth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a flowchart showing the operation of the fifth embodiment of the present invention.

In the first to third embodiments, the pseudo distance correction value of each satellite (all visible satellites) was calculated. In the fifth embodiment, as a function of the processor, a process for minimizing the displacement even when the combination of satellites is changed is added.

Hereinafter, this processing method will be described. For example, when there are five or more visible satellites, the position of the base station is calculated by taking a set of four satellites from among them. At this time, the pseudo distance correction values calculated in the first to third embodiments are used.

Next, the position of the base station is calculated from another combination. This process is performed for the number of valid combinations. For example, when there are five visible satellites, there are up to ₅ C ₄ = 5 combinations, and when there are ₆ visible satellites, there are up to ₆ C ₄ = 15 (maximum) combinations. The position of the base station is calculated for the combination, and all are different. The pseudo-range correction value of each satellite is further optimized so that the difference between the different positions is minimized. Therefore, in the user's terminal, the position error is smaller than that of the conventional D-GPS device, and the position shift when the combination of satellites is changed is minimized.

The case where there are five visible satellites will be described with reference to the flowchart of FIG. In step 40, a combination of selecting four out of five visible satellites, ₅ C ₄
Are calculated, there are five types. Here, the reason why four are selected is that four-dimensional parameters (X, Y, Z, T) are obtained.

In step 41, the combination of the most accurate satellite arrangements is selected from the combinations. This combination of the most accurate satellite arrangements is known in advance by theoretical calculations. Next, in step 42, the position of the base station is calculated from the combination using the pseudo distance correction values obtained in the first to third embodiments.

In step 43, the remaining one satellite and three satellites are selected from the four satellites, and a combination that provides a highly accurate arrangement is selected. The combination of the arrangement of the satellites with high accuracy is also known in advance by theoretical calculation. Next, in step 44, the fifth pseudo distance correction value is calculated using the combination so as to minimize the difference from the position of the base station obtained in step 42.

Embodiment 6 FIG. A sixth embodiment of the present invention will be described with reference to FIG.

Using the high precision clock 13 of the fourth embodiment shown in FIG. 7, the optimization of the position of the base station calculated by the combination of three satellites can be performed by the same processing method as that of the fifth embodiment. Therefore, in the user's terminal, the position error is smaller than that of the conventional D-GPS device, and the position shift when the combination of satellites is changed is minimized.

Embodiment 7 FIG. Embodiment 7 Embodiment 7 of the present invention will be described with reference to FIG. FIG. 9 is a block diagram showing a configuration of Embodiment 7 of the present invention.

In FIG. 9, reference numeral 14 denotes a high-precision altimeter connected to the processor 4D.

In the seventh embodiment, as shown in FIG. 9, a highly accurate altimeter 14 is used, and a two-dimensional base station position is calculated by three satellites. Then, similarly to the fifth embodiment,
The position of the base station is calculated using successive combinations of different satellites, and the pseudo-range correction value is optimized so that the satellite combination error is minimized. Therefore, at the user's terminal,
The position error is smaller than the conventional D-GPS device,
The displacement of the change of the satellite combination is minimized.

Embodiment 8 FIG. Embodiment 8 Embodiment 8 of the present invention will be described with reference to FIG. FIG. 10 is a block diagram showing a configuration of the eighth embodiment of the present invention.

In the eighth embodiment, as shown in FIG.
Using a high-precision clock 13 and an altimeter 14, two satellites are used to calculate the position of a two-dimensional base station, and the combinations are sequentially obtained. As in the fifth embodiment, the satellite combination error is minimized. Thus, the pseudo distance correction value is optimized. Therefore, at the user's terminal, the position error is the conventional D-GP
The number of S units is small, and the displacement of the change of the combination of satellites is minimized.

[0049]

As described above, the differential GPS device according to claim 1 of the present invention has a D-GPS
Base that calculates the pseudo distance correction value of the user and notifies the user terminal
It is a predetermined distance from the station to measure the exact distance from the base station.
An auxiliary station provided at a remote location,
Is the satellite that receives the satellite information transmitted from the artificial satellite.
2 based on the GPS antenna and the satellite information.
Calculates the second measured value of radio wave propagation delay time between satellite and auxiliary station
Outgoing GPS receiver, said base station comprising:
The first to receive satellite information transmitted from the satellite
GPS antenna and the artificial satellite based on the satellite information
Calculate the first measured value of the radio wave propagation delay time between the star and the base station
And a first GPS receiver that performs measurement by means other than GPS.
Location information of the base station and the base station and the auxiliary
An input device for inputting relative position information between stations;
Radio waves between the satellite and the base station based on station location information
Calculating a first calculated value of the propagation delay time,
Location information of the base station and the phase between the base station and the auxiliary station;
Radio transmission between the satellite and the auxiliary station based on the position information
Calculating a second calculated value of the transport delay time, and calculating the first measured value;
And the first difference between the first calculated value and the second measured value
Calculating a second difference between the second calculated values,
If the difference between the two is equal, a pseudo distance based on the first difference
Calculating a correction value, and when the first and second differences are different,
Indicates the position of the base station on the line connecting the satellite and the base station.
The position of the auxiliary station is determined by the line connecting the satellite and the base station.
The first and second differences on a line parallel to
Are shifted based on the first difference so that
Because it has a processor for calculating a pseudorange correction value each, false
The similar distance correction value can be obtained with high accuracy, and there is an effect that the position locating at the user terminal becomes highly accurate.

The differential GPS device according to a second aspect of the present invention, as described above,
Cross at right angles to the line connecting the auxiliary stations and pass through the base station
Further comprising a second auxiliary station disposed on the line
The second auxiliary station transmits the satellite information transmitted from the artificial satellite.
A third GPS antenna for receiving the broadcast information,
The radio wave propagation delay between the satellite and the second auxiliary station
And a third GPS receiver for calculating a third measured value between
And the processor of the base station, the position information of the base station and
By means other than GPS input by the input device
Relative position between the base station and the second auxiliary station measured
Radio waves between the satellite and the second auxiliary station based on the location information
Calculating a third calculated value of the propagation delay time;
Calculating a third difference between the value and the third calculated value,
The location of a station, an auxiliary station and a second auxiliary station to the base station,
Station, a second auxiliary station, and the first, second and
And the first is shifted so that the third difference is minimized.
Since the pseudo distance correction value is calculated based on the difference , the pseudo distance
There is an effect that the correction value can be obtained with higher accuracy .

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a processing method according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a second embodiment of the present invention.

FIG. 5 is a diagram for explaining a processing method according to a second embodiment of the present invention;

FIG. 6 is a diagram showing an arrangement of auxiliary stations according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the fifth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a seventh embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of an eighth embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a conventional differential GPS device.

[Explanation of symbols]

1 GPS antenna, 2 GPS receiver, 3 input device,
4A, 4B, 4C, 4D, 4E processor, 5 GPS antenna, 6 GPS receiver, 7 base station, 8 auxiliary station, 9
Artificial satellites, 13 high precision clocks, 14 high precision altimeters.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-3431 (JP, A) JP-A-7-71977 (JP, A) US Patent 5,332,322 (US, A) Prem & Dr. Mohan, "Wide Area Differential GPS-Potential for Accurate Global Navigation," Proc. Annu. Meet. Insitute of Navigation, Vol. 48th (US) (1992), pp. 243-253 (58) Field surveyed (Int. Cl. ⁷ , DB name) G01S 5/00-5/14 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A method of calculating a pseudo distance correction value of D-GPS.
Separated from the base station for notifying the user terminal by a predetermined distance from which the exact distance can be measured.
An auxiliary station provided at a location where the satellite information is transmitted from an artificial satellite.
Based on the received second GPS antenna and the satellite information
The second of the radio wave propagation delay time between the artificial satellite and the auxiliary station.
A second GPS receiver for calculating an actual measurement value, wherein the base station transmits satellite information transmitted from the artificial satellite.
A first GPS antenna for receiving the broadcast information,
Of the radio wave propagation delay time between the artificial satellite and the base station.
A first GPS receiver for calculating the actual measurement value of
Position information of the base station measured by external means and the
Input for inputting relative position information between a base station and the auxiliary station
A device and the satellite based on location information of the base station.
To calculate a first calculated value of the radio wave propagation delay time between the mobile station and the base station
And the location information of the base station and the
The satellite and the satellite based on the relative position information between the auxiliary stations
Calculating a second calculated value of the radio wave propagation delay time with the auxiliary station;
A first difference between the first measured value and the first calculated value and
Calculating a second difference between the second measured value and the second calculated value
And when the first and second differences are equal, the first difference
The first and second pseudo distance correction values are calculated based on
If the difference is different, the position of the base station is
The position of the auxiliary station on the line connecting
Parallel to the line connecting the star and the base station and in front of the line passing through the auxiliary station
The first and second differences are shifted so that they are equal to each other before
A processor for calculating a pseudo distance correction value based on the first difference
And a differential GPS.
apparatus. 2. A right angle to a line connecting said base station and said auxiliary station.
And a second line located on a line passing through the base station
Further comprising an auxiliary station , wherein the second auxiliary station is transmitted from the satellite
A third GPS antenna for receiving satellite information;
Radio propagation between the satellite and a second auxiliary station based on the information
A third GPS receiver for calculating a third actually measured delay time
And the processor of the base station, the position information of the base station and the
Measured by means other than GPS input by the input device
Relative position information between the determined base station and the second auxiliary station.
Radio propagation between the satellite and a second auxiliary station based on the information
A third calculated value of the delay time is calculated, and the third measured value is calculated.
Calculating a third difference between the third calculated value and the base station;
The positions of the auxiliary station and the second auxiliary station are determined by the base station, the auxiliary station and
The first, second and third sub-stations are located on the plane containing the second auxiliary station.
Are shifted from each other so that the difference between
2. The differential GPS device according to claim 1, wherein the pseudo-range correction value is calculated based on the pseudo-range correction value .