JPH04326080A - Method for detecting position of moving body - Google Patents

Abstract

PURPOSE:To correct the position measuring error by a global positioning system(GPS) on the side of a moving body by together using a second position measuring means capable of specifying a position with high accuracy on the side of the moving body to calculate a position measuring error vector by the GPS. CONSTITUTION:A GPS satellite is a system capable of specifying a position by receiving the signals transmitted from a plurality of satellites on a plurality of orbits. When a second position measuring means 20 is effective, the output of the second position measuring means 20 is subtracted from the position measuring result due to a GPS by an error quantity calculation means 101 to calculate an error vector. Thereafter, when a sign post signal is not obtained or matching can not be normally executed by the advance to a region where no road data is present, the calculated error vector is used to perform positional correction to the position measuring result due to the GPS. That is, in a correction means 102, correction is performed by subtracting the error vector from the result of a GPS position measuring means 100.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the position of a moving object such as an automobile, and more particularly to a method for increasing the accuracy of positioning using a GPS receiver.

0002

[Prior art] GPS (Global Position
ning System) is a positioning system that uses satellite signals, and can calculate a position by simultaneously receiving three or four satellite signals.

However, with GPS, the effects of the ionosphere,
It is known that intentionally manipulating orbit information broadcast from satellites can degrade accuracy. the result,
Positioning results as shown in FIG. 4 are obtained. This is point O
This is the case when measured at a fixed point. To some extent,
The result is that they drift from P to Q while scattering.

[0004] A differential GPS reception system is considered effective for dealing with such errors whose error components change over time. In this method, a GPS satellite signal is received at a fixed point whose position is known with high accuracy, the positioning error vector Vc in FIG. 4 is determined, and the information is broadcast to the moving object. The mobile body subtracts the error vector Vc transmitted from the fixed station from its own positioning result to obtain a correction result.

[0005] Regarding this differential type GPS reception system, Japanese Patent Laid-Open No. 108982/1982 is a known example.

[0006]

[Problem to be solved by the invention] The above conventional differential type GP
In the S reception system, the problem is the means of transmitting information from the fixed station to the mobile unit. Unless a mobile object is always present within a station, wireless communication must be used as a means of communication. However, the use of wireless is not freely possible, and there are legal and cost issues. Furthermore, when a mobile object travels in urban areas, mountainous areas, etc., communication itself may not be possible.

The present invention has been made to solve the problems of the conventional technology described above, and can achieve the same effects as a differential type GPS receiving device only on the mobile side without the support of a fixed station. The purpose is to provide a method that allows you to obtain the following.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object of the invention, in the present invention, a positioning error vector by GPS is determined by using a second position measuring means that can specify the position with high accuracy on the moving object side. After that, when the second position measuring means becomes unusable, the positioning result by GPS is corrected using the error vector to maintain high accuracy.

[0009]

[Operation] The second position measuring means is a sign post or something similar, or a map matching method that improves accuracy by comparing sensor data with a digital road map. GPS satellite signals can be received almost all the time, and output is always available. On the other hand, a sign post signal is obtained when a moving object happens to pass near a sign post. In map matching, when matching with the road map is performed normally, the
The location can be determined. In this way, when information is obtained by the second position measuring means, the measurement error by GPS is determined. After that, when the sign post signal cannot be obtained or the map matching cannot be executed normally due to progressing to an area where no road data exists, the error vector obtained last time is used to perform GP
Position correction is performed on the positioning result obtained by S.

0010

[Embodiment] Next, one embodiment of the present invention will be described with reference to FIG.

In FIG. 1, 100 is a GPS positioning means;
101 is an error amount calculation means, 102 is a correction means, and 20 is a second position measurement means. A GPS satellite is a system that can specify a position by receiving signals transmitted from a plurality of satellites orbiting in a plurality of orbits. As for the receiving means, a known technique can be used. GPS positioning requires direct reception of satellite radio waves.
Continuous measurement is possible except in special places such as tunnels. The GPS receiving means outputs position information at a cycle of, for example, one second. However, as shown in FIG. 4, if the satellite signal is intentionally manipulated or the state of the ionosphere changes, the positioning result will have an offset added to it. As shown in FIG. 4, an error vector Vc is generated with respect to the true position. At this time, the measurement result at the fixed point is the error vector Vc
The results can be said to vary randomly around the .

[0012] The error vector changes relatively slowly over time. Therefore, after a certain error vector is obtained, it is possible to obtain sufficient accuracy even if correction is performed using the correction value for a while.

Second, the position measuring means 20 needs to be relatively accurate for the above purpose. For example, a sign post installed next to a road is ideal. Signposts usually take the form of spot communication that uses light or electromagnetic waves to form a relatively small communication zone, and by communicating digital data, accurate coordinate information can be transmitted to a moving object. I can tell you. Sign posts are equipment located on the ground, so they may be difficult to use. In such a case, a position detection result obtained by map matching may be used as the second position specifying means 20. The map matching method is
It is effective as a correction means for so-called dead reckoning using a sensor means that is a combination of a direction sensor, a vehicle speed sensor, etc., and its technology is well known.

[0014] While map matching is operating normally and effectively, it is ineffective when driving in an area where digital road data is not available and measurement by GPS is considered unnecessary. In that case, the position can be detected with high precision by performing measurement using GPS and using the error vector obtained so far.

In any case, when the second position measuring means 20 is effective, the error amount calculating means 101 uses the GPS
The output of the second position detection means 20 is subtracted from the positioning result obtained by , and the error vector Vc is obtained. Furthermore, the correction means 102 subtracts the error vector from the result of the GPS positioning means 100 to perform correction.

FIG. 2 shows a detailed processing block diagram when combined with map matching. The same numbers as in FIG. 1 indicate the same contents, and the explanation will be omitted. The second position detecting means 20 in FIG. 1 is replaced by a sensor means 200, a map matching means 201, a mismatching determining means 203, and an initial position presetting means 202.

Normally, since the vehicle is traveling in an area where road map data exists, map matching is normally performed and highly accurate position detection is performed by the map matching means 201. In such a state, the mismatching determining means 203 outputs false, that is, a matching state. Therefore, the initial position presetting means 20
2 does not issue a preset request to the map matching means 201. When the map matching is not performed normally due to entering an area where there is no map data, the mismatching detection means 203 notifies the user that the mismatching state is true, that is, a mismatching state exists. At this time, the initial value presetting means 202 provides the map matching means 201 with the following information:
Request an initial position preset.

[0018] Since the correction for positioning by GPS is as described above, the explanation will be omitted.

FIG. 3 shows the block size and grams of a device that implements the processing described in FIG. 2. The GPS receiving means 100 can be configured by an antenna 300 and a GPS receiver 301. Each of these can be realized using known techniques. The control device 302 is a device using a so-called microprocessor, and has a storage device (memory).
The vehicle speed sensor 303, which operates according to a program stored in the vehicle, generates pulses at regular intervals as the vehicle advances. The direction sensor 304 is, for example, a geomagnetic sensor or a gyroscope, and detects the direction in which the vehicle is traveling, and is used in conjunction with the vehicle speed sensor 303 to perform advance navigation. External storage device 30
5 stores road map data used for map matching in the form of digital data. Control device 30
2, the current position is determined by comparing the estimated position obtained by dead reckoning with the road map. The control device 302 further displays the current position of the vehicle together with the map information on the display device 306.

FIG. 5 shows an operational flow of the control device 302. The operation program of the control device 302 operates according to this flow. First, in step 400, necessary initialization is performed. This includes initializing peripherals and memory. Next, in step 401, map matching is performed. Next, in step 402, the positioning results output by the GPS receiver 301 are processed. Specifically, processing for converting the coordinate system used in the GPS receiver 301 into the coordinate system used in map matching is also included. Next, in step 403,
The status of map matching is checked. If it is determined that there is no mismatch state, the positioning error by GPS is calculated in step 405. The method has already been described. If it is determined in step 404 that there is a mismatching state, step 40
In step 6, the GPS positioning output is corrected using the previously determined positioning error. And step 407
Then, the initial position for map matching is preset, and the process returns to step 401 to repeat the above process.

FIG. 6 shows a flow corresponding to the error amount calculation means 101. First, in step 600, it is determined whether there is a matching state. This determination can be easily made by simply monitoring the internal variables of map matching. Next, in step 601, ΔX=Gx−Mx

...(Math. 1) ΔY=Gy-My Here, Gx, Gy...GPS receiver's X, Y coordinate output Mx, My...X, Y coordinate output formula by map matching, the error amount X, Y Find the coordinate values ΔX and ΔY. Next, in step 602, the amount of error is stored.

FIG. 7 shows a flow corresponding to the correction means 102. First, in step 700, the X coordinate is corrected. That is, Cx=Gx-ΔX

(Equation 2) Here, Cx... is calculated as the X coordinate value of the correction output.

Next, in step 701, the Y coordinate is corrected using the following equation.

Cy=Gy−ΔY

(Equation 3) Here, Cy...Y coordinate value of corrected output FIG. 8 shows a processing flow corresponding to the mismatching determination means 203. First, in step 800, variables representing the internal processing state of the map matching process are checked to see if there is no matching state over a certain abnormality. As a result, if it is determined that there is no matching state,
In step 801, a mismatching lag is set. In the opposite case, the mismatching flag is cleared in step 802.

[0025] Now, the literature: “The Effect
f Selective Availability
n Differential GPS Correct
ions” G.T. Kremer et al., NAVIGATI
ON Magazine Vol. 37, No. 1, 39p, 1990, it is stated that at a certain point in time, the amount of error determined increases with time. In an example where the second position measuring means is a sign post, it is expected that the period of position detection will be very long. In other words, the previously determined error amount gradually loses its effectiveness. In such a case, it is necessary to set the valid time of the error vector and perform error correction.

FIG. 9 shows a flow for performing this process. This flow may be added after step 503 in FIG. 5, for example. First, in step 900, it is determined whether the elapsed time from the timing when the error amount was calculated last time has exceeded a certain value. If not, in step 902, a flag indicating prohibition of correction is cleared. if,
If the time has elapsed, a correction prohibition flag is set in step 901. This flag is used to bypass steps 506 and 507 in FIG.

[0027]

As described above, according to the present invention, it is possible to correct errors in positioning by GPS on the mobile side without receiving help from a fixed station.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating one embodiment of the present invention.

FIG. 2 is a diagram illustrating FIG. 1 in more detail.

FIG. 3 is a configuration diagram of a device that implements the functions shown in FIG. 2;

FIG. 4 is a diagram illustrating an example of results obtained by GPS positioning means.

FIG. 5 is a diagram illustrating the flow of the main program.

FIG. 6 is a flow diagram illustrating an error calculation method.

FIG. 7 is a flow diagram illustrating error correction.

FIG. 8 is a flow diagram for determining the state of map matching.

FIG. 9 is a flowchart illustrating control of the Abutseiku flag.

[Explanation of symbols]

20...Second position measuring means, 100...GPS positioning means,
101...Error amount calculation means, 102...Correction means, 201...
Map matching method.

Claims (5)

[Claims] [Claim 1] GPS (Global Position
a first position measuring means and a second position measuring means based on a signal (indicating system), and while the second position measuring means is operating normally, the difference between the measurement result by the first measuring means and the first position measuring means is determined. 1. A method for detecting a position of a moving body, comprising: error calculating means for calculating the error; and means for correcting the output of the first measuring means based on the result of the error detecting means. 2. The method for detecting a position of a moving body according to claim 1, wherein the second position detecting means is a map matching means. 3. A position detecting means for a moving body according to claim 1, wherein said second position detecting means is a sign post receiving means. 4. The means for detecting the position of a moving body according to claim 1, wherein a valid time period for the output of the error calculating means is set. 5. In claim 2, the output of the error calculation means is obtained only when the map matching means is operating normally, and when the map matching means is not operating normally, A method for detecting the position of a moving body, characterized in that the output of the error correction means is preset as the initial position of the map matching means.