JPH10185600A - Vehicle position correcting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the position accurately by determining a position measuring accuracy and correcting the position when the accuracy comes within a specified range. SOLUTION: A position detector 26 for own vehicle detects the absolute position of its own vehicle based on detection signals from a distance sensor, an azimuth sensor and a GPS receiver using a CPU. In order to detect an accurate absolute position, a vehicle position correction unit 27 corrects the position. Positioning accuracy of GPS depends on the number and arrangement of satellites and the measurements fluctuate due to the error. State change of a positioning satellite can be grasped by monitoring DOP(dilution of precision). The smaller the DOP value, the higher the accuracy. The position can be corrected accurately by monitoring the DOP value, correcting the position when the DOP value is sustained for a predetermined time within a specified range and discarding an absolute positioning data obtained under bad state of the positioning satellite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position correcting apparatus for measuring a current absolute position using a GPS (Global Positioning System) satellite in a car navigation system or the like.

[0002]

2. Description of the Related Art In a car navigation system or the like, a GPS is used to measure a current absolute position of a vehicle. However, in the case of the absolute position measurement by the GPS, there is a time lag in the processing time during traveling or the like, and the position correction has a large error compared to when stopped. In addition, since the movement vector cannot be calculated while the vehicle is stopped, position correction by map matching cannot be performed. Accordingly, position correction is performed without stopping map matching while the vehicle is stopped.

When the absolute position of a vehicle is measured by GPS, a GPS is used as an absolute position / azimuth detecting means, a gyro, a geomagnetic sensor is used as an azimuth detecting means, and a vehicle speed pulse or the like is used as a distance detecting means. But G
It is said that the absolute position measurement by the PS usually has a distance error of 20 to 200 m. If the position is corrected simply under the condition that the vehicle is stopped, the error may be increased.

[0004]

The accuracy of the absolute position measurement by GPS depends on the number of satellites and the arrangement of the satellites. Even when the number of positioning satellites is three, the position can be detected by GPS, but the error increases because three-dimensional positioning cannot be performed. When the number of positioning satellites is four or more, three-dimensional positioning is possible. However, when the arrangement of satellites is poor and the satellites are not dispersed and concentrated in one place, the number of positioning satellites is four or more. Even in such a case, the positioning accuracy deteriorates and the error increases.

Further, when correcting the position of a vehicle that is continuously stopped, a state where the positioning accuracy is good continues, and then the positioning accuracy becomes poor. For example, when waiting for a signal, a large vehicle or the like receives a signal from a satellite. It is possible to block out. Also, GPS
Has a mechanism to intentionally generate an error.
If the data obtained by the above is used as it is, there is a possibility that an incorrect position is corrected.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to accurately measure an absolute position under the above-mentioned circumstances and to correct the position of a vehicle.

[0007]

When the absolute position of the vehicle is measured by GPS while the vehicle is stopped and the position is corrected,
In the present invention, the accuracy of the position measurement by the GPS is grasped, the position is corrected when the accuracy is within a certain range, and the measured value obtained when the positioning accuracy is poor is not used.

Further, the data of the absolute position measurement by the GPS is divided according to the accuracy, weighted, and the data with high accuracy is preferentially adopted to correct the position. G
In order to cope with the mechanism of intentionally generating PS error,
This error is removed by using DGPS (Differential GPS), and the position is corrected by performing accurate position measurement.

Further, when correcting the position, it is determined whether the measured value is a measured value obtained by using DGPS, weighted, and the measured value is adopted to correct the position.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vehicle position correcting device according to the present invention will be described below with reference to the drawings. FIG. 1 shows a basic hardware configuration including a vehicle position correcting device according to the vehicle navigation system of the present invention. In FIG. 1, a vehicle is provided with a distance sensor 11 based on a vehicle speed pulse or the like, and an azimuth sensor 12 formed of any one of a geomagnetic sensor, a vibration gyro, an optical fiber gyro, a gas rate sensor, or the like, or a combination thereof. The detection signal is supplied to a central processing unit (CPU) 13. On the other hand, G
PS (Global Positioning System) Satellite 1
Also provided is a GPS receiver 15 for receiving and demodulating the radio waves from 4, and supplies the demodulated GPS signal to the CPU 13.
The CPU 13 obtains the current absolute position based on the integrated distance data obtained by integrating the detection signal from the distance sensor 11 and the azimuth data from the azimuth sensor 12. In addition, CD
-Storage device 1 such as ROM, IC card, hard disk, etc.
6, the map data stored in advance is read and displayed on the display device 18, and the current position of the vehicle is displayed on the map.
The main memory 17 stores information for navigation.

FIG. 2 is a block diagram of a display device of a vehicle navigation system having the vehicle position correcting device of the present invention. In FIG. 2, an input unit 21 includes a switch provided on a display 18 (FIG. 1) of the display device or a touch switch displayed on a screen. The user uses the input device 21 to set a departure point and a destination point for the route search device 22. The route search device 22 searches for an optimum route using the map data 23 and the route search data stored in the storage device 16 (FIG. 1), and outputs the result to the route guide device 24 and an output unit 25 such as a display device. Output to The route search device 22 and the route guidance device 24 are the same as those in FIG.
It is controlled by the PU 13. On the other hand, the map data is output to the route guidance device 24 and the vehicle position detection device 26. The vehicle position correction device 27 of the present invention is provided in the vehicle position detection device 26. The output from the vehicle position detection device 26 is output to the route guidance device 24 and sent to the output unit 25, and the current position of the vehicle is displayed on a map.

The self-vehicle position detecting device 26 includes a CPU 13 shown in FIG.
The absolute position of the own vehicle is detected from the detection signal from the PS receiver 15. At this time, the position is corrected by a vehicle position correcting device in order to detect the accurate absolute position. Next, an outline of correction by the position correction device when the vehicle stops according to the present invention will be described. Note that, for example, a vehicle speed pulse is used as the distance detecting means. The vehicle speed pulse is output in proportion to the rotation speed of the tire.

As described above, the positioning accuracy by the GSP differs depending on the number of satellites and the arrangement of the satellites, and the measured values vary due to errors. However, a change in the state of the positioning satellite such as the number and arrangement of the satellites is caused by a DOP (Dilution of Precision).
on) can be grasped by monitoring.
The GPS has a maximum of eight satellites, and the number of satellites, the arrangement of the satellites, the signal level of other satellites, and the like are input to the DOP to determine the state of the positioning satellites, and a predetermined calculation is performed. , DPO values are obtained. The smaller the DOP value, the better the accuracy. Therefore, even if the GPS is in the positioning state as described above, the error may be large. Therefore, the DOP is monitored, and the position is corrected when the DOP value is within a certain range for a certain period of time. If the absolute positioning position obtained at the time is not used, the position can be accurately corrected.

In the position correction of a vehicle that is continuously stopped, if the positioning accuracy is good and the positioning accuracy is poor after that, for example, a large car or the like receives a signal from a satellite when waiting for a signal. In the case of blocking, the absolute position measured in the bad state is not used, and the correction can be made with the absolute position obtained by the previous positioning. Further, when the measurement is continuously performed for a certain period of time, the arrangement of the satellites and the like change, and the accuracy changes. Therefore, an average of the measured position data is obtained, and the data is used for correction. Then, at that time, the measured position data is divided according to the accuracy, an average value is calculated, weighted, and data with higher accuracy is preferentially adopted. In order to derive an average value by weighting in this case, the following equation is used. Average value = (1-K) x Σ (accurate position data) / (accurate position data) + K x Σ (inaccurate position data) / (inaccurate position data) ( 0 ≦ K ≦ 1) In the above equation, whether the measurement value is at a high-accuracy position or at a low-accuracy position can be determined by, for example, the DOP value.

Further, the GPS has a mechanism for intentionally generating an error. DGPS can be used to remove this error. FIG. 3 shows an outline of DGPS. As shown in FIG. 3, the DGPS measures the positioning error by the GPS 14 at the fixed reference station 19 whose longitude and latitude are known, transfers the error as correction data, and receives the error on the vehicle side. At step 20, the error is removed from the absolute position measured by the GPS, and is used to correct the position of the vehicle.

The error in DGPS is said to be several meters,
The accuracy is several tens to several hundred times higher than that of a normal GPS. If it is not possible to transfer correction data from DGPS,
Since positioning is performed by GPS, whether or not DGPS can be used is also a criterion indicating positioning accuracy. When DGPS is not available, even if it is determined that the positioning state of the satellite is good, there is a possibility that the error will be increased if the position is corrected because of the intentional error as described above. Therefore, in such a case, the absolute position obtained by the positioning is not immediately corrected, but is corrected by weighting according to the accuracy.

For example, the correction is made by the following equation. Correction position = (1-H) x measurement position + H x current position
(0 ≦ H ≦ 1) According to the above equation, if correction is made, for example, at H = 0.5, even if a deliberate error is input from the GPS, the correction position is an intermediate value and does not largely deviate. Next, an embodiment of the vehicle position correcting device of the present invention will be described with reference to FIG. The operation of the embodiment described below is controlled by the vehicle position correction device 27 of FIG.

FIG. 4 is a flowchart showing the embodiment. First, a position correction operation is started (S1). At this time, the counter n = 0, the number of measurement data m1 = 0, m2 =
0, data addition value X1 = 0, Y1 = 0, X2 = 0, Y
2 = 0 and the continuous stop flag flag = 0. n is a counter for determining whether or not the vehicle has been stopped continuously, and is a counter for counting the state where the vehicle speed is 0.

If the vehicle has been stopped for a certain period of time, for example, if the vehicle speed is 0 for 1 second (S3), n is counted as 1 (S4), and the value of n is added every second while the vehicle is stopped. If n becomes larger than the preset continuous stop determination coefficient N, it is determined that the vehicle is continuously stopped (S5). In this case, if N = 10 is set, it is determined that the vehicle stops continuously if the stop time exceeds 10 seconds. If it is determined that the vehicle has been stopped continuously, the data up to that point is discarded and the determination of the accuracy is started. Then, the determination of the accuracy of the data received 11 seconds or more after the start of the continuous stop count is started.
It is determined that it is good or not (S6).

The accuracy is determined, for example, by determining the number of positioning satellites and DO.
This is done by the P value. In this case, the number of positioning satellites is P,
When the DOP value is D, it is determined that: ・ When the number of positioning satellites> P1 and DOP <D1, → Excellent ・ When the number of positioning satellites> P2 and DOP <D2 → Good ・ Other → Not possible D1 <D2). It should be noted that other factors may be added to the accuracy determination as needed, or may be replaced with other components.

The data determined to be excellent are sequentially added in S7. Here, X1 and Y1 are the added values of the position data, and x and y are the position data measured by the absolute position detecting means. Where X is the X coordinate, that is, longitude, Y is the Y coordinate,
That is, it represents latitude. m is the number of data, and m1 is the number of data determined to be excellent, which is used to calculate the average of the data determined to be excellent. The data determined to be good are sequentially added in S8. Here, X2 and Y2 are the added values of the position data, and x and y are the position data measured by the absolute position detecting means. Here, X represents the X coordinate, that is, longitude, and Y represents the Y coordinate, that is, latitude. m2 is the number of data determined to be good, and is used to calculate the average of the data determined to be good. Data determined to be unacceptable is not used. And
During continuous stops, excellent and good data is collected.

Next, when the count number exceeds N and N + N '(N
('Is a correction determination coefficient).
9). If No, that is, if not n> N + N ′,
It is determined that the number of data is not sufficient, and the process returns to S3. Ye
If s, that is, if n> N + N ', the continuous stop flag is raised and the flag
= 1 (S10), and the excellent and good data numbers m1 and m2 of the data measured so far in S11 are determined.

In S11, if m1 <M1 and m2 <M2, the number of data m1 and the number of good data m2 are smaller than the predetermined data determination numbers M1 and M2, the number of data is small and the reliability is low. Is determined,
The process ends and ends (S12), and no position correction is performed. After the end (S12), the operation is started again (S12).
Returning to 1), the same operation is repeated.

If it is determined that m1 <M1 and m2 <M2 are not satisfied, then it is determined whether m1 <M1 (S1).
3). If No is determined, it is next determined whether m2 <M2 (S15). Here, if it is also determined as No, that is, if the number of good and good data is sufficient, the weighted averages Gx and Gy of the longitude and latitude of the absolute position detected during stoppage using the added value are calculated. It is calculated by the following equation (S17).

Gx = (1−K) × X1 / m1 + K × X2 / m2 Gy = (1−K) × Y1 / m1 + K × Y2 / m2 where K is a weighted average count, and in the above case, K <0. 5,
For example, K = 0.2, and the weight of the superior data is increased. Next, the longitude and latitude of the corrected current position, Hx,
Hy is calculated by the following equation (S18).

Hx = (1−H) × Gx + H × X (X is the longitude of the current position before correction) Hy = (1−H) × Gy + H × Y (Y is the latitude of the current position before correction) Is a weighted average count, and when positioning is performed using DGPS, the data is reliable. Therefore, H = 0 is replaced with the current value. On the other hand, if positioning is performed without using DGPS, there is a possibility that a measured value may include a deliberate error. Therefore, H> 0.5 is used, and the measured value is weighted without using the measured value as it is. To adjust the current position.

After the above calculation result is calculated, flag =
It is determined whether it is 1 (S19). If No, that is, if the vehicle is not continuously stopped, the corrected current position is calculated and the process ends (S20), and the position correction ends. f
When lag = 1, that is, when the vehicle is still continuously stopped,
Initial values are set (S21), and the process returns to S3. In this case, the initial values are n = N and flag = 0.

On the other hand, if it is determined in S13 that m1 <M1, the count K is set to K = 1. Then, since m2 <M2 is not satisfied in this case, No is determined in S15 and the process proceeds to S17. The calculation in S17 and S18 is K =
It is set to 1 and the excellent measurement value is ignored because the number of data is small, and the weighted average Gx is calculated based on the value calculated from the good measurement value.
And Gy are calculated.

On the other hand, if it is determined in S15 that m2 <M2 (in this case, m1 <M1 is not satisfied), the count K is set to K = 0 (S16), and the flow proceeds to S17. S17,
The calculation in S18 is set to K = 0, good measurement values are ignored because the number of data is small, and weighted averages Gx and Gy are calculated based on the calculated values of excellent measurement values. afterwards,
The longitude Hx of the current position corrected using the above Gx and Gy
And the latitude Hy are calculated. The following is the same as the above flow.

The process ends at S20, but returns to the start (S1) again and the same operation is repeated.

[0031]

The accuracy of the absolute position measurement by the GPS varies depending on the number of satellites and the arrangement of the satellites. In the present invention, however, the accuracy of the position measurement by the GPS is grasped, and when the accuracy is within a certain range. The position is corrected, and the measured value obtained when the positioning accuracy is poor is not used. Further, in the present invention, the position measurement data by the GPS is divided according to the accuracy, weighted, and the position correction is performed by preferentially using the data with high accuracy. Therefore, even if the measurement accuracy of the absolute position by the GPS varies, a highly accurate measurement value can be obtained.

In order to cope with a mechanism for intentionally generating a GPS error, DGPS (Differential G) is used.
(PS) to eliminate this error and measure the absolute position accurately to correct the position. Therefore, it is possible to perform high-precision position correction without increasing the error by position correction. it can. Further, when the DGPS cannot be used, the position is corrected by weighting and using the measured value, so that even if an error is included, the position is not significantly corrected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic hardware configuration of a vehicle position correction device in a vehicle navigation system.

FIG. 2 is a block diagram of a display device of a vehicle navigation system including the vehicle position correction device of the present invention.

FIG. 3 is a diagram showing an outline of DGPS.

FIG. 4 is a flowchart showing an embodiment of the vehicle position correcting device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Distance sensor 12 ... Azimuth sensor 13 ... CPU 14 ... GPS satellite 15 ... GPS receiver 16 ... Storage device 17 ... Main memory 18 ... Display device 19 ... Reference station 20 ... Vehicle 21 ... Input unit 22 ... Route search device 23 ... Map Data 24: route guidance device 25: output unit 26: own vehicle position detection device 27: vehicle position correction device

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[Procedure amendment]

[Submission date] March 24, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

Further, when correcting the position of the vehicle that is in continuous stop, followed by good positioning accuracy state, then positioning accuracy becomes bad, for example, large vehicles such as when the signal waiting a signal from a satellite It can be blocked. Further, since the GPS has a mechanism for intentionally generating an error, if data obtained by the GPS is used as it is, there is a possibility that an incorrect position is corrected.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

As described above, the positioning accuracy by GPS differs depending on the number of satellites and the arrangement of the satellites, and the measured values vary due to errors. However, changes in the state of positioning satellites, such as the number and arrangement of satellites, are caused by DOP (Dilution of Precision).
n) can be grasped by monitoring. G
The PS has a maximum of eight satellites. In order to grasp the state of the positioning satellite, the number of satellites, the arrangement of the satellites, the signal level of other satellites, and the like are input to the DOP, and a predetermined calculation is performed. , DOP values are obtained. The smaller the DOP value, the better the accuracy. Therefore, even if the GPS is in the positioning state as described above, the error may be large. Therefore, the DOP is monitored, and the position is corrected when the DOP value is within a certain range for a certain period of time. If the absolute positioning position obtained at the time is not used, the position can be accurately corrected.

Claims (5)

[Claims] 1. A vehicle position correction device of a vehicle position detection device for estimating a position of a vehicle using an absolute position detection unit, an absolute direction detection unit, and a distance detection unit, which is installed on a vehicle by a GPS. Means for determining whether or not the vehicle is in a stopped state, means for determining the accuracy of position measurement when the vehicle is in a stopped state for a certain period of time or more, and means for holding a measured value when the accuracy is within a certain range. A vehicle position correcting device that corrects the vehicle position based on a measured value when is within a certain range. 2. A vehicle position correction device of a vehicle position detection device for estimating the position of a vehicle using an absolute position detection means, an absolute azimuth detection means, and a distance detection means installed on a vehicle by a GPS, wherein the vehicle has a predetermined time or more. Means for determining whether or not the vehicle is stationary, means for determining the accuracy of position measurement when the vehicle has been stationary for a certain period of time or more, means for separately holding measured values according to the accuracy at the time of measurement, and A vehicle position correction device comprising means for weighting a measured value in accordance with the weight, and correcting the vehicle position with the weighted measured value. 3. The vehicle position correcting device according to claim 1, wherein the position is corrected only when the measured values are equal to or more than a predetermined number. 4. The vehicle position correcting device according to claim 1, wherein an error of measurement by GPS is removed by DGPS. 5. The vehicle position correcting device according to claim 1, wherein the degree of position correction is weighted when DGPS cannot be used.