JPH11295411A - Dgps position locating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a DGPS position locating system which can compute a relative position while a moving station designated as a master station is used as a reference, by a method wherein position data whose time is identical for the master station and a slave station is used, the relative position is computed and the position of every mobile using the master station as a reference is displayed on a digital map. SOLUTION: By a computer 5 in a master station 2a, an input device 6 is used, and the master station 2a is set. Then the master station 2a executes a processing operation. When a GPS receiver 4 outputs an own position, the sampling time Tp and the position Pp (t) of the master station 2a are updated. Then the position Pp (t) is smoothing-processed, and a reference position Ps (t) is obtained. In addition, as data on the master station 2a, the reference position Ps (t), the position Pp (t), the sampling time Tp and a capturing satellite number SNp (t) are transmitted via a communication device 7. At the same time, a digital map is read out from an external storage device, and the computed position Ps (t) is displayed on the digital map as the position of the master station 2a. The communication device receives position data on a slave station 2b. When the sampling time Tc of the position data on the slave station 2b is equal to the time Tp of the master station 2a, the relative coordinates RPc of the slave station 2b is computed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS (Global Posi
DGPS (Diff), which is configured to measure with a positioning system and calculate relative positions with each other using position data measured at the same time.
eriental GPS) positioning system.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional position locating system using DGPS. Reference numeral 1 denotes the entire fixed station system, and reference numeral 2 denotes the entire mobile station system. The fixed station 1 includes a GPS antenna 3 for receiving radio waves from GPS satellites,
GP that detects current location coordinates and current time from PS satellite information
S receiver 4 and computer 5 for calculating correction data from known coordinates of the fixed station and current position coordinates detected by GPS
An input device 6 for inputting known fixed station coordinates to the computer 5, a communication device 7 for transmitting the calculated correction data and receiving the position data of the mobile station, a transmission / reception antenna 8 of the communication device 7, and road data. And a display 10 for displaying the current location of each mobile station together with the digital map. The mobile station 2
A GPS antenna 3 for receiving radio waves from GPS satellites,
A GPS receiver 4 for detecting the current location coordinates and the current time from the received GPS satellite information, a communication device 7 for receiving correction data from the fixed station 1 and transmitting its own position data, a transmitting / receiving antenna 8 of the communication device 7, A computer 5 for calculating a more accurate self-position using correction data from a fixed station; an external storage device 9 for recording a digital map including road data; a calculated self-position and positions of the fixed station and other mobile stations Is displayed together with a digital map.

[0003] Next, a description will be given of a method of grasping the mutual positions between mobile stations in a conventional system. FIG. 10 shows the fixed station 1.
6 is a processing flow of the computer 5 of FIG. First, the fixed station 1 inputs known fixed station coordinates from the input device 6 to the computer 5 and sets the fixed station coordinates (step 1). Next, the GPS receiver 4 and the communication device 7 are initialized,
It monitors whether the receiver 4 outputs position data or the communication device 7 receives data (steps 2, 3, and 6). G
When the PS receiver 4 detects its own position and outputs its own position data, the computer 5 calculates GPS correction data using the own position data of the GPS receiver output and the fixed station coordinates set in Step 1 (Step 4). Also,
The calculated correction data is transmitted using the communication device 7 (step 5). When the communication device 7 receives the position data of the mobile station, it updates the position of the mobile station (step 7).
Then, the updated position of the mobile station is displayed on the digital map (step 8). FIG. 11 is a processing flow of a program executed by the computer 5 of the mobile station 2. First, the mobile station 2 initializes the GPS receiver 4 and the communication device 7, and monitors whether the GPS receiver 4 outputs position data or the communication device 7 receives data (steps 1 and 2).
2, 6). When the GPS receiver 4 outputs the self-position data, the self-position is corrected and updated using the position data and the latest correction data transmitted from the fixed station 1 (step 3). Subsequently, the position data corrected in step 4 is transmitted using the communication device 7, and in step 5, the digital map is read from the external storage device 9 and the updated position is displayed on the digital map. Further, when the communication device 4 receives the position data of another mobile station, the position of the moving body is updated and displayed on a digital map (steps 8 and 5). Further, when the communication device 4 receives the correction data from the fixed station 1, it updates it as the latest correction data (step 9).

[0004]

Since the conventional DGPS position locating system is configured as described above, when the mobile station is in an area where the correction data transmitted from the fixed station cannot be received, the error can be sufficiently corrected. There was a problem that the accuracy could not be improved and the accuracy deteriorated. In addition, there is a problem that it is necessary to install a fixed station at a known coordinate, and the installation of the fixed station is troublesome.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and exchanges position data between mobile stations without installing a fixed station and sets a relative position based on a mobile unit designated as a master station. The purpose of the present invention is to obtain a DGPS position locating system for calculating a general position.

[0006]

Means for Solving the Problems DG in the first invention
The PS position locating system includes a GPS antenna for receiving radio waves from GPS satellites, a GPS receiver for detecting current location coordinates and current time from received GPS satellite information, an external storage device for recording a digital map including road data, A communication device for transmitting and receiving position data by communicating between the bodies, a transmitting and receiving antenna of the communication device, a computer for calculating a relative position of each mobile object, and an input device for designating a master station or a slave station; And a display for displaying the calculated position of each mobile unit on a digital map. The mobile unit designated as the master station captures the position data and the time data of the latitude and longitude of the current position acquired by the GPS receiver. The reference position data of the master station obtained by smoothing the number data and the position data of the GPS satellites is periodically transmitted by the communication device. The base station periodically transmits the position data and time data of the latitude and longitude of the current location acquired by the server, calculates the relative positions of the master station and the slave station using the same time position data, and determines the master station. The reference position of each moving object is displayed on a digital map.

A DGPS position locating system according to a second aspect of the present invention includes a GPS antenna for receiving radio waves from GPS satellites, a GPS receiver for detecting current location coordinates and current time from received GPS satellite information, road data and elevation values. An external storage device storing a digital map including data,
A communication device for transmitting and receiving position data by communicating between moving objects, a transmitting and receiving antenna of the communication device, a computer for calculating a relative position of each moving object, and an input device for designating a master station or a slave station And a display for displaying the calculated position of each mobile unit on a digital map. The mobile unit designated as the master station captures the position data and the time data of the latitude, longitude and altitude of the current position acquired by the GPS receiver. The base station base position data obtained from the altitude value of the current location calculated from the latitude and longitude of the base station obtained by smoothing the number data and position data of the GPS satellites and the digital map obtained from the digital map, and the communication device periodically. The mobile station designated as a slave station periodically transmits the location data and time data of the latitude, longitude, and altitude of the current location acquired by the GPS receiver, and uses the same-time position data of the master station and the slave station, respectively. Calculating a relative position, in which the location of each mobile relative to the master station to be displayed on a digital map.

A DGPS position locating system according to a third aspect of the present invention includes a GPS antenna for receiving radio waves of GPS satellites, a GPS receiver for detecting current location coordinates and current time from received GPS satellite information, and a digital signal including road data. An external storage device that records a map, an altitude detection device that detects the altitude of the current location, a communication device that communicates between mobile units to transmit and receive position data, a transmitting and receiving antenna of the communication device, A mobile unit designated as a master station, comprising a computer for calculating a general position, an input device for designating a master station or a slave station, and a display for displaying the calculated position of each mobile unit on a digital map. In this method, the position data and the time data of the latitude, longitude and altitude of the current position acquired by the GPS receiver, the number data and the position data of the captured GPS satellites are smoothed and obtained. The communication device periodically transmits reference position data of the master station obtained from the latitude and longitude of the master station and the altitude of the current position detected by the altitude detection device, and the mobile device designated as the slave station obtains the current position obtained by the GPS receiver. The position data and time data of the latitude and longitude are periodically transmitted, and the relative positions of the master station and the slave stations are calculated using the same time position data, and the position of each mobile unit with respect to the master station is calculated. The position is displayed on a digital map.

The DGPS position locating system according to a fourth aspect of the present invention can capture a GPS antenna for receiving radio waves from a GPS satellite, a GPS receiver for detecting current position coordinates and current time from received GPS satellite information, and a GPS satellite. If the current location cannot be detected without using it, an inertial navigation device that complements the position data during that time, an external storage device that stores digital map data including road data and elevation value data, and transmits and receives position data by communicating between moving objects A communication device;
A transmitting / receiving antenna of the communication device, a computer for calculating a relative position of each mobile unit, an input device for designating a master station or a slave station, and displaying the calculated position of each mobile unit on a digital map. A mobile unit designated as a master station is obtained from the position data and time data of the current location's latitude, longitude and altitude acquired by the GPS receiver, the number data of the captured GPS satellite, the inertial navigation device, and the digital map. The communication device periodically transmits the reference position data of the master station, and the mobile unit designated as the slave station periodically transmits the position data and the time data of the latitude / longitude / altitude of the current location obtained by the GPS receiver. If the number of captured satellites of the GPS receiver is less than 4, transmit the position data supplemented by the inertial navigation system,
The relative position of each of the master station and the slave station is calculated using the same time position data, and the position of each mobile unit with respect to the master station is displayed on a digital map.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows a first embodiment of the present invention. The mobile station includes one mobile station set to the master station 2a and a plurality of mobile stations set to the slave station 2b. Each mobile station uses a GPS antenna 3 for receiving radio waves of GPS satellites, and present location coordinates based on the received GPS satellite information. And a GPS receiver 4 for detecting the current time, an external recording device 9 for recording a digital map including road data, a communication device 7 for communicating between mobile units to transmit and receive position data, and a transmitting / receiving antenna of the communication device 8, a computer 5 for calculating a relative position of each mobile unit, an input device 6 for designating a master station or a slave station, and a display 10 for displaying the calculated position of each mobile unit on a digital map. It is composed of 2 and 3 show a processing flow of a program executed by the computer 5 of FIG.

First, the operation when the master station 2a is set will be described with reference to the flowchart of FIG. Master station 2a
When the computer 5 is set as a master station using the input device 6 (step 1), the GPS receiver 4 and the communication device 7 are initialized (step 2), and the processing of the master station after step 4 is executed. . In steps 4 and 9, it is monitored whether the GPS receiver 4 outputs the position data or the communication device 7 receives the data. When the GPS receiver 4 outputs its own position data, in step 5, the sampling time Tp and the position Pp (t) of the master station are updated. Next, a reference position PS (t) is obtained by smoothing Pp (t) (step 6). Further, at step 7, reference position data PS (t), own position data Pp (t), sampling time Tp, and captured satellite number SNp (t) are transmitted using the communication device 7 as master station data. At the same time, in step 8, the digital map is read from the external storage device 9 and the calculated reference position PS (t) is displayed on the digital map as the position of the master station. When the communication device 7 receives the position data of the slave station, and the sampling time Tc of the position data of the slave station is equal to the sampling time Tp of the master station, the calculation of Expression 1 is performed to calculate the relative coordinates RPc of the slave station. (Steps 9, 10, 11, 1
2). At this time, the error component included in the position data of the master station and the slave station is canceled by the principle of DGPS, and the relative coordinates RPc with high accuracy can be obtained.

[0012]

(Equation 1)

Next, using the reference position PS (t) of the master station and the relative coordinates RPc of the slave station, the position of the slave station is calculated by Equation 2 to update the position of the slave station (step 1).
3).

[0014]

(Equation 2)

Finally, in step 8, the updated position of the slave station is displayed on a digital map.

Next, the operation when the mobile station is set to the slave station will be described with reference to the flowchart of FIG. When the setting is made to the slave station by the input device 6, after the GPS receiver 4 and the communication device 7 are initialized in the computer 5 of the slave station 2b, FIG.
The processing after A shown in the flowchart of FIG. In steps 1 and 6, it is monitored whether the GPS receiver 4 outputs position data or the communication device 7 receives data. G
When the PS receiver 4 outputs the position data and the same as the captured satellite number of the master station, the PS receiver 4 updates the position data Po (t) of the own station and uses the communication device 7 to determine the own position Pc (t) (= Po).
(T)) and transmit the sampling time Tc (steps 1, 2, 3, and 4). If the acquired satellite number is not the same as that of the master station in step 2, the GPS receiver is controlled so as to become the same acquired satellite (step 5). If the communication device 7 receives data from the slave station and the sampling time Tp of the master station is equal to the sampling time Tc of the slave station, the operation of Equation 1 is executed to obtain the relative coordinates RPc of the slave station (step). 6, 7, 8, 9). Next, in step 10, the operation of Expression 2 is executed to calculate the position of the slave station from the reference position PS (t). When the data received by the communication device 7 is the master station data (step 12), the master station data is updated (step 13), and the arithmetic operations of the equations (1) and (2) are executed in the step 14 to determine the position of the own station. Pc (t) ′ is calculated. Finally, in step 11, a digital map is read from the external storage device 9, and each slave station P is displayed on the digital map.
The position of c (t) ′ and the position Ps (t) of the master station are displayed.

Embodiment 2 FIG. FIG. 4 shows a second embodiment of the present invention. While Embodiment 1 is a two-dimensional position locator, the present invention is extended to a three-dimensional position locator. The mobile station includes one mobile station set to the master station 2a and a plurality of mobile stations set to the slave station 2b. Each mobile station uses a GPS antenna 3 for receiving radio waves of GPS satellites, and present location coordinates based on the received GPS satellite information. And a GPS receiver 4 for detecting the current time, an external storage device 9 for recording a digital map including road data and altitude data, a communication device 7 for communicating between mobile objects to transmit and receive position data, and a communication device for the communication device. A transmitting / receiving antenna 8, a computer 5 for calculating a relative position of each mobile unit, an input device 6 for designating a master station or a slave station, and a display for displaying the calculated position of each mobile unit on a digital map. And a vessel 10. FIG.
6 shows a processing flow of a program executed by the computer 5 of FIG.

FIG. 5 is a flowchart showing the operation of the master station according to the present invention. The difference from FIG. 2 is that the position data Pp (t) is updated with the three-dimensional data of the latitude, longitude, and altitude in step 5, and that Pp (t) is updated in step 6.
The calculated altitude value zs _m location from a digital map of the external storage device 9 by using the xs _m and ys _m obtained by smoothing, in that obtaining the reference position PS (t). As a result, the GPS can compensate for altitude data with inaccurate accuracy and perform more accurate position location. Steps 12 and 13
The operations of Expressions 1 and 2 in are three-dimensional vector operations.

FIG. 6 is a flowchart showing the operation of the slave station according to the present invention. The difference from FIG. 3 is that in step 3, the position data Po (t) is updated with three-dimensional data of latitude, longitude and altitude. Similarly to the processing in the master station, the operations of Expressions 1 and 2 in Steps 9, 10, and 14 are three-dimensional vector operations.

Embodiment 3 FIG. 7 shows a third embodiment according to the present invention. In the second embodiment, the altitude value of the reference position is measured by using the altitude value data of the digital map. In the present invention, the altitude value is measured by using the altitude detecting device. The mobile station includes one mobile station set to the master station 2a and a plurality of mobile stations set to the slave station 2b. Each mobile station uses a GPS antenna 3 for receiving radio waves of GPS satellites, and present location coordinates based on the received GPS satellite information. And a GPS receiver 4 for detecting the current time, an external storage device 9 for recording a digital map including road data, an altitude detecting device 11 for detecting a current altitude, and transmitting and receiving position data by communicating between mobile bodies. A communication device 7; a transmitting / receiving antenna 8 of the communication device; a computer 5 for calculating a relative position of each mobile object; an input device 6 for designating a master station or a slave station; And a display 10 for displaying the position on a digital map. FIG. 8 shows a processing flow of a program executed when the computer 5 of FIG. 7 is set as a master station. In the present invention, the processing flow of the slave station is the same as in FIG.

FIG. 8 shows the operation when the master station is set.
The differences from FIG. 5 will be described using the flowchart of FIG. According to the present invention, in step 6, the latitude and longitude components of the reference position are set to the Pp
(T) the calculated and smoothed, but elevation zs _m is detected by the altitude detecting unit.

Embodiment 4 FIG. 9 shows a fourth embodiment according to the present invention. The present invention is configured by using an inertial navigation device together. The mobile station comprises one mobile station set to the master station 2a and a plurality of mobile stations set to the slave station 2b. Each mobile station receives a GPS satellite radio wave.
Antenna 3, GPS receiver 4 for detecting current location coordinates and current time from received GPS satellite information, external storage device 9 storing digital map including road data and elevation value data, and when GPS receiver cannot detect position Inertial navigation device 12 that complements the position, communication device 7 that communicates between mobile units to transmit and receive position data, transmission / reception antenna 8 of the communication device, and computer that calculates the relative position of each mobile unit 5, an input device 6 for designating a master station or a slave station, and a display 10 for displaying the calculated position of each mobile unit on a digital map. 10 and 11 show a processing flow of a program executed by the computer 5 of FIG.

Operation when set to master station FIG. 1
0 will be described. If four or more GPS satellites cannot be acquired in step 5, the current reference position PS (t) is detected from the inertial navigation device and the Pin is detected.
The flag is set to s, so that it is understood that the value is a complement value (steps 11 and 12). The master station data is transmitted together with the flag set in step 9. If four or more GPS satellites have been captured in step 5,
Steps 6 and 7 are executed, and in step 8, the initial value of the inertial navigation system is set to PS (t). When the master station receives the position data of the slave station, it checks the flag (step 15),
If the value is the complement value, the position data of the slave station is displayed on a digital map in step 10 without performing the arithmetic processing of Equations 1 and 2. Thus, even when four or more GPS satellites cannot be captured, the space between them can be complemented by the inertial navigation device, and the position of each mobile station can be ascertained.

Operation when set to slave station FIG. 1
1 will be described. If four or more GPS satellites cannot be acquired in step 2, the current reference position Po (t) is detected from the inertial navigation device and the Pin is detected.
s, and a flag is set so that it is understood that the value is a complement value (steps 8 and 9). Also, even when the number of GPS satellites is four or more, if a satellite different from the master station is captured, the GPS receiver is controlled to capture the same satellite as the master station, and then the current reference position Po (t) is changed. Flags are set as Pins detected from the inertial navigation device, and flags are set so as to be recognized as complementary values (steps 3, 7, 8, and 9). The slave station data is transmitted together with the flag set in step 5. If four or more GPS satellites have been captured in step 2, step 4 is executed. When the slave station receives the position data of another slave station, the flag is checked (step 12).
In step 15, the position is displayed on the digital map without performing the arithmetic processing of equation (2). If the data of the master station is received, the flag is checked (step 17). If the value is the GPS value, the data of the master station is updated to calculate the position of the own station. Initial values of the navigation device are set (steps 18, 19, 20). With this, GPS
Even when four or more satellites cannot be acquired, the space between them can be complemented by the inertial navigation device, and the position of each mobile station can be ascertained.

[0025]

As described above, according to the first aspect, the master station does not need to be fixed, and the sampling is synchronized on the basis of the master station. DGPS can be realized.

According to the second aspect of the present invention, the altitude is calculated using digital map data having the altitude data, and the three-dimensional three-dimensional data is used to compensate for the low accuracy of the altitude specific to GPS. There is an effect that the relative positional relationship can be accurately located.

Further, in the third invention, an altitude detecting device is incorporated as a means for acquiring altitude, so that the present invention can be applied not only to the ground but also to a moving object in the sky.

According to the fourth aspect of the present invention, since the inertial navigation device is incorporated, even if four or more GPS satellites cannot be acquired, the present location is complemented by using the output data of the inertial navigation device. There is an effect that the relative positional relationship between the moving bodies can be stably located.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a DGPS position locating system according to the present invention.

FIG. 2 is a flowchart showing an operation of a master station in the first embodiment of the DGPS position locating system according to the present invention.

FIG. 3 is a flowchart showing an operation of a slave station in the first embodiment of the DGPS position locating system according to the present invention.

FIG. 4 is a diagram showing a second embodiment of the DGPS position locating system according to the present invention.

FIG. 5 is a flowchart showing an operation of a master station in a second embodiment of the DGPS position locating system according to the present invention.

FIG. 6 is a flowchart showing the operation of the slave station in the second embodiment of the DGPS position locating system according to the present invention.

FIG. 7 is a diagram showing Embodiment 3 of a DGPS position locating system according to the present invention.

FIG. 8 is a flowchart showing the operation of the master station in the third embodiment of the DGPS position locating system according to the present invention.

FIG. 9 is a diagram showing a fourth embodiment of the DGPS position locating system according to the present invention.

FIG. 10 is a flowchart showing the operation of a master station in a fourth embodiment of the DGPS position locating system according to the present invention.

FIG. 11 is a flowchart showing the operation of the slave station in the fourth embodiment of the DGPS position locating system according to the present invention.

FIG. 12 is an overall configuration diagram of a conventional DGPS position locating system.

FIG. 13 is a flowchart showing an operation of a fixed station of the conventional DGPS position locating system.

FIG. 14 is a flowchart showing an operation of a mobile station in the conventional DGPS position locating system.

[Explanation of symbols]

1 fixed station, 2 mobile station, 3 GPS antenna, 4G
PS receiver, 5 computer, 6 input device, 7
Communication device, 8 transmitting / receiving antenna, 9 external storage device,
10 display, 11 altitude detection device, 12 inertial navigation device.

Claims (4)

[Claims] 1. GPS (Global Position)
GPS which receives the radio wave of the satellite
An antenna, a GPS receiver for detecting current position coordinates and current time from received GPS satellite information, an external storage device for recording a digital map including road data, and a communication device for transmitting and receiving position data by communicating between moving objects. , A transmitting / receiving antenna of the communication device, a computer for calculating the relative position of each mobile unit, an input device for designating a master station or a slave station, and displaying the calculated position of each mobile unit on a digital map. For a mobile unit designated as a master station, the data obtained by the GPS receiver are obtained by smoothing the latitude and longitude position data and time data of the current location, the number data and the position data of the captured GPS satellite, and obtained. The communication device periodically transmits the reference position data of the master station, and the mobile unit designated as the slave station uses the GPS receiver to obtain the position data of the latitude, longitude and altitude of the current location and the time. Data is transmitted periodically, the relative positions of the master station and slave stations are calculated using the same time position data, and the position of each mobile unit with respect to the master station is displayed on a digital map. DGPS, characterized in that
(Differential GPS) position location system. 2. A GPS antenna for receiving radio waves of GPS satellites, a GPS receiver for detecting current position coordinates and current time from received GPS satellite information, and an external storage device for recording a digital map including road data and elevation value data. When,
A communication device for transmitting and receiving position data by communicating between moving objects, a transmitting and receiving antenna of the communication device, a computer for calculating a relative position of each moving object, and an input device for designating a master station or a slave station And a display for displaying the calculated position of each mobile unit on a digital map. The mobile unit designated as the master station captures the current location latitude / longitude position data and time data acquired by the GPS receiver. GPS
The base station's reference position data obtained at the altitude calculated from the latitude and longitude of the base station obtained by smoothing the satellite number data and position data and the digital map and the altitude value calculated from the digital map, and periodically transmitted by the communication device, The mobile unit designated as the slave station periodically transmits the position data and time data of the latitude, longitude, and altitude of the current location acquired by the GPS receiver, and uses the relative position data of the master station and the slave station at the same time. A DGPS position locating system, wherein a position is calculated, and a position of each mobile object with respect to a master station is displayed on a digital map. 3. A GPS antenna for receiving radio waves of a GPS satellite, a GPS receiver for detecting current position coordinates and a current time from received GPS satellite information, an external storage device for recording a digital map including road data, An altitude detecting device for detecting altitude, a communication device for transmitting and receiving position data by communicating between mobile objects, a transmitting and receiving antenna of the communication device, a computer for calculating a relative position of each mobile object, and a master station It consists of an input device for designating a mobile station or a slave station, and a display for displaying the calculated position of each mobile unit on a digital map. For a mobile unit specified as a master station, the latitude, longitude and altitude of the current location obtained by a GPS receiver Location data and time data, and the number and position data of the captured GPS satellites, and the latitude and longitude of the base station obtained by smoothing the data and the height of the current location detected by the altitude detection device. The base station's reference position data obtained in degrees is periodically transmitted by the communication device, and the mobile unit designated as the slave station periodically transmits the current location latitude / longitude altitude position data and time data obtained by the GPS receiver. Calculate the relative position of each of the master station and the slave station using the same time position data, and display the position of each mobile unit with respect to the master station on a digital map. DGPS location system. 4. A GPS antenna for receiving a radio wave of a GPS satellite, a GPS receiver for detecting a current position coordinate and a current time from the received GPS satellite information, and position data when the current position cannot be detected because the GPS satellite cannot be captured. An inertial navigation device that complements the above, an external storage device that records digital map data including road data and elevation value data, and a communication device that communicates between mobile units to transmit and receive position data,
A transmitting / receiving antenna of the communication device, a computer for calculating a relative position of each mobile unit, an input device for designating a master station or a slave station, and displaying the calculated position of each mobile unit on a digital map. A mobile unit designated as a master station is obtained from the position data and time data of the current location's latitude, longitude and altitude acquired by the GPS receiver, the number data of the captured GPS satellite, the inertial navigation device, and the digital map. The base station transmits the reference position data of the master station periodically by the communication device, and the mobile unit designated as the slave station periodically transmits the position data and the time data of the latitude, longitude and altitude of the current position obtained by the GPS receiver. If the number of captured satellites of the GPS receiver is less than 4, transmit the position data supplemented by the inertial navigation system,
The relative position of each of the master station and the slave station is calculated using the same position data at the same time, and the position of each mobile unit with respect to the master station is displayed on a digital map. DGPS position location system.