JPH06331369A - Running bearing computation system - Google Patents

Abstract

PURPOSE:To enable the computation of a running bearing of a vehicle accurately. CONSTITUTION:A bearing data (GPS bearing) measured in position with a GPS and a bearing data (sensor bearing) measured with an angle sensor 5a are preserved into a bearing data memory section 6d-2 together with position measuring time and when map matching becomes impossible, a vehicle position correcting section 6d corrects an offset angle using multiple sets of the GPS bearing data and sensor bearing data within time set previously from the present time. An offset angle corrected is added to the sensor bearing to compute an actual running bearing of the vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling azimuth calculation method, and more particularly, to a traveling azimuth calculation of a navigation system in which a three-dimensional positioning function by GPS (Grobal Positioning System) is added to self-contained navigation using a distance sensor and an angle sensor. Regarding the scheme.

[0002]

2. Description of the Related Art A navigation system reads map data corresponding to the current position of a vehicle from a map data storage unit such as a CD-ROM and draws it on a display screen.
The vehicle position mark is moved on the map, or the vehicle position mark is fixedly displayed at a fixed position on the display screen (for example, the center position of the display screen), and the map is scrolled according to the movement of the vehicle. The map data is (1)
It is composed of a road layer consisting of road data, road link data, intersection data, etc., (2) a background layer for displaying objects on the map, and (3) a character layer for displaying city names, etc. The map image displayed on the screen is generated based on the background layer and the character layer, and the map matching process and the guidance route search process are performed based on the road layer. In such a navigation system, it is essential to measure the current position of the vehicle. Therefore, a measurement method (self-contained navigation) that measures the vehicle position using a distance sensor and an angle sensor mounted on the vehicle
A GPS measurement method using satellites and satellites (satellite navigation) has been put to practical use. The vehicle position measurement by self-contained navigation can measure the vehicle position at a relatively low cost, but there is a problem that the position measurement cannot be performed with high accuracy, and correction processing such as map matching processing is required. In addition, while satellite navigation can detect an absolute position, it has a drawback that the position cannot be detected in a place where satellite radio waves are blocked, such as a tunnel or a building.

In a self-contained navigation device,
The vehicle position is detected as follows by integration based on the outputs of the distance sensor and the angle sensor. FIG. 8 is an explanatory diagram of a vehicle position detection method by self-contained navigation. The distance sensor outputs a pulse each time the vehicle travels a certain unit distance L ₀ , and the reference azimuth (θ = 0) is set on the X axis. The positive direction is the positive direction, which is the counterclockwise direction from the reference direction. The previous vehicle position is the point P ₀ (X ₀ , Y ₀ ), and the traveling direction of the vehicle at the point P ₀ is θ.
₀ , unit distance L ₀ The output of the angle sensor at the time of traveling is Δ
If it is θ ₁ , the change amount of the vehicle position is ΔX = L ₀ · cos (θ ₀ + Δθ ₁ ) ΔY = L ₀ · sin (θ ₀ + Δθ ₁ ), and the traveling direction θ at this point P _{1 1} and position (X ₁ ,
Y ₁ ) is given as θ ₁ = θ ₀ + Δθ ₁ (1) X ₁ = X ₀ + ΔX = X ₀ + L ₀ · cos θ ₁ (2) Y ₁ = Y ₀ + ΔY = Y ₀ + L ₀ · sin θ ₁ (3) It can be calculated by vector composition.

Therefore, if the angle (offset angle) between the actual traveling azimuth of the vehicle at the start point and the reference azimuth is given, the offset angle is added to the traveling azimuth (hereinafter referred to as sensor azimuth) obtained by the equation (1). As a result, the actual traveling direction of the vehicle, that is, the absolute traveling direction can be obtained. Further, if the current position of the vehicle at the start point is given, the vehicle position can be detected in real time by the equations (2) and (3), and the vehicle position mark and the traveling locus can be displayed on the road. The offset angle and the vehicle position at the start point are set as follows, for example. FIG. 9 is an explanatory view of a display screen in such a case, where RD is a road, S is a start point, CM is a vehicle position mark, and TR is a traveling locus. Prior to traveling, the joystick on the operation panel is operated to position the vehicle position mark CM at the start point S on the map. After that, when the vehicle is driven in the direction A along the road RD, the navigator calculates the vehicle position and the sensor azimuth by calculating the equations (1) to (3), and follows the dotted line in FIG. 9 (a). The vehicle position mark CM is moved and displayed. That is,
The vehicle position mark CM and the traveling locus TR are displayed in a direction deviated from the road on which the vehicle is actually traveling by an offset angle θoff. In this way, the reason why the vehicle position mark is not displayed on the road is that the traveling direction is the sensor azimuth obtained by setting the X-axis direction to the direction of θ = 0 (reference azimuth).

If the navigator can recognize the offset angle θoff, the traveling azimuth can be obtained as the absolute traveling azimuth by adding the offset angle θoff to the sensor azimuth obtained by the equation (1) as described above, and the vehicle position mark CM The traveling locus TR can be put on the road actually traveling. Therefore, the vehicle continues to run, and when the vehicle moves to a point Q where a clear instruction can be given on the map, the vehicle stops and the joystick is operated to move the vehicle position mark CM to the point Q. As a result, the traveling locus TR is also translated and displayed as shown in FIG. 9 (b). Then, the angle correction key provided on the operation panel is operated to rotate the traveling locus TR by θoff about the point Q to start the locus starting point at the start point S.
If it is located at, the offset angle θoff can be recognized by the navigator (see FIG. 9 (c)). After that, the navigator can obtain the absolute traveling azimuth by adding the offset angle θoff to the sensor azimuth obtained by the equation (1), and by setting the mark position to the current vehicle position, the following (2), ( The vehicle position can be calculated by the equation (3). As a result, when the vehicle travels, the vehicle position mark CM is correctly moved and displayed on the road.

[0006] In such self-contained navigation, errors occur as the vehicle travels.
Are accumulated and the vehicle position deviates from the road. So the map
By matching the vehicle position with the road data by matching processing
Fix on the road. Various proposals for map matching methods
Has been done. The first map matching method is
Save (position and direction for each predetermined mileage) and
Find a road on the map that has the same shape as the line trajectory, and point it on that road.
Map matching the vehicle position mark with the
Turn matching). Second map matching method
The method is a projection method. Figure 10 shows the projection method
It is an explanatory view of up matching. Vehicle position is point P
_i-1(X_i-1, Y_i-1) And the vehicle direction is θ_i-1Met
And Point P_i-1More constant distance L₀(For example, 5m)
When the relative orientation is Δθ_iIf so, self-contained navigation vehicle
Point P at both positions_i′ (X_i′, Y_i′) And P_iVehicle direction at '
θ_iIs the following equation θ_i= Θ_i-1+ Δθ_i  X_i′ = X_i-1+ L₀・ Cos θ_i  Y_i′ = Y_i-1+ L₀・ Sin θ_i Required by.

[0007] At this time, 'a link possible from the taking down perpendicular, point P _i' (a) point P _i heading theta _i in
And the angle formed by the link is within a certain value, and the length of the perpendicular line drawn from the point P _i ′ to the link is within a certain distance. Here, the link LKa ₁ (the straight line connecting the nodes Na ₀ and Na ₁ ) of the direction θa ₁ on the road RDa and the road RD
This is a link LKb ₁ (a straight line connecting the nodes Nb ₀ and Nb ₁ ) with the direction θb ₁ on b. Then, (b) link LKa from point P _i ′
_The lengths of the vertical lines RLia and RLib dropped to ₁ and LKb ₁ are obtained, and the shorter link is used as a matching candidate. Here, the link is LKa ₁ . (c) The traveling locus SHi connecting the points P _i-1 and P _i ′ is translated in the direction of the perpendicular line RLia until the point P _{i -1} is on the link LKa ₁ (or on the extension line of the link LKa ₁ ). The moving points PT _i-1 and P _{i of} the points P _i-1 and P _i ′.
T _i ′ is obtained, and (d) Finally, PT _i ′ is centered on the point PT _i−1.
Is moved on the link LKa ₁ (or on the extension of the link LKa ₁ ) to obtain the moving point, and the corrected vehicle position P _i
(X _i , Y _i ). The vehicle orientation at the corrected vehicle position P _i remains θ _i .

By the way, in the self-contained navigation, when the error becomes large and the vehicle position deviates greatly from the road, the vehicle position cannot be map-matched with the actual current position on the road. That is, the first map matching method makes it impossible to find a road having the same shape as the traveling locus, and the second method makes it impossible to find a road that satisfies the matching condition. When the map matching becomes impossible in this way, the navigation does not make sense, and the vehicle must be stopped and the vehicle position mark must be positioned at the actual vehicle position on the map to restart the navigation.
However, such a method has extremely poor operation performance. Therefore, if GPS is incorporated into a self-contained navigation system and map matching becomes impossible, the position of the vehicle and the direction data obtained from the GPS are used to map match the vehicle position with the current position of the vehicle, and the traveling direction of the vehicle. A fix has been made.

The correction of the traveling azimuth is carried out by correcting the GPS azimuth θgi at a plurality of points (n points) and a plurality of absolute traveling azimuths (θsi +) measured by the self-contained navigation at the same point.
θoff: θsi is the sensor azimuth and θoff is the average value of the difference from the offset angle θc = (1 / n) · Σ {θgi- (θsi + θoff)} (i = 1,2, ... n) The calculation is performed according to (4), and the offset angle θoff so far is corrected by the average value θc. That is, a new offset angle θoff is calculated by the following equation θoff + θc → θoff (5). After that,
Using this new offset angle θoff and the sensor azimuth θsi measured by self-contained navigation, the absolute traveling azimuth θai is calculated by the following equation θsi + θoff → θai (6). Although includes an error of about a maximum ± 15 ⁰ The GPS orientation, G (4) below
Since the ± error of the PS azimuth data cancels each other, the azimuth data can be corrected with high accuracy.

[0010]

There is an offset drift in an angle sensor such as a vibrating gyro and shows a certain value even when stationary. Since the rotation angle is obtained by integrating the angle sensor output (angular velocity), the error included in the sensor azimuth increases with time due to the offset drift.
Then, when map matching becomes impossible, (4),
Correct the offset angle using equation (5). From the above, the value of the current offset angle θoff deviates from the correct offset angle value as far back as the present time. By the way, conventionally, in the equation (4), the latest n GPS azimuths θgi, the sensor azimuth θsi at the same point, and the latest offset angle θoff are unconditionally used, and when the previous value is used as the sensor azimuth θsi. There is. This is GP
In S, the position and direction cannot be detected in a place where satellite radio waves are blocked, such as in a tunnel or a building, and if you encounter traffic congestion or waiting for a signal in such a state, you cannot save the direction data, resulting in the following This is because the interval until the azimuth data is saved becomes long.

As described above, when the value before the sensor azimuth θsi is used, there is a difference between θoff used at the time of detecting the sensor azimuth and the current θoff, and the difference becomes large as it goes back in the past. (Θsi + θoff) in Eq. (4) does not show an accurate absolute running direction. Therefore, in the conventional method, an error is included in the newly calculated offset angle θoff, and as a result, the absolute traveling azimuth obtained by the equation (6) includes an error, which makes it impossible to detect the correct absolute traveling azimuth. There is. From the above, an object of the present invention is to obtain an offset angle with a small error by not using old azimuth data of a predetermined time before the current time, and as a result, a travel azimuth that can accurately calculate the absolute travel azimuth of the vehicle. It is to provide a calculation method.

[0012]

According to the present invention, there is provided a means for setting a difference between an azimuth (sensor azimuth) measured by an angle sensor and an actual traveling azimuth of a vehicle as an offset angle, and a sensor azimuth. A means for calculating the traveling direction (absolute traveling direction) of the vehicle by adding the offset angle, GP
A means for storing the azimuth data (GPS azimuth) measured by S and the azimuth data (sensor azimuth) measured by the angle sensor together with the positioning time, and when the map matching becomes impossible, it is preset from the current time. And a means for correcting the offset angle using multiple sets of GPS orientation and sensor orientation in time.

[0013]

The difference between the azimuth measured by the angle sensor (sensor azimuth) and the actual traveling azimuth of the vehicle is set as an offset angle, and the offset azimuth is added to the sensor azimuth to calculate the traveling azimuth of the vehicle. The azimuth data measured by the GPS (GPS azimuth) and the azimuth data measured by the angle sensor (sensor azimuth) are stored together with the positioning time. When map matching becomes impossible, the offset angle is corrected using multiple sets of GPS direction and sensor direction within the preset time from the current time, and the running direction of the vehicle is determined using the new offset angle. Calculate
With this configuration, the offset angle can be accurately corrected without using the old azimuth data of a predetermined time before the current time, and as a result, the absolute traveling azimuth of the vehicle can be accurately calculated.

[0014]

Embodiments (a) Overall Configuration of First Embodiment of the Present Invention FIG. 1 is a configuration diagram of a navigation system according to a first embodiment of the present invention, in which 1 is a CD-R for storing map information.
OM, 2 is a control panel, 3 is a GPS receiver that receives radio waves from satellites to measure the current position of the vehicle, 4 is a multi-beam antenna that receives radio waves from each satellite, and 5 is a self-contained navigation sensor. Reference numeral 5a is a relative azimuth sensor (angle sensor) that detects the rotation angle of the vehicle such as a vibration gyro, 5b is a distance sensor that generates one pulse for each predetermined traveling distance, 6 is a map and vehicle position mark drawing processing, and is optimal. A system controller having a microcomputer configuration for performing route search processing, map matching processing, and the like, and a display device 7.

Map information Map information is composed of (1) road layer, (2) background layer for displaying objects on the map, (3) character layer for displaying names of cities, towns and villages, etc. There is.
Among them, the road layer includes road link data RLDT, node data NDDT, and intersection data C as shown in FIG.
It has an RDT. The road link data RLDT gives the attribute information of the relevant road, and all the road links
It is composed of data such as the number of roads, the number of each node forming the road, the road number (road name), and the type of road (national road, highway, other). Also, intersection data CRDT
Is a set of nodes (referred to as an intersection composing node) closest to the intersection among the nodes on the link connecting the intersections on the map, and the node data NDDT constitutes a road. It is a list of all nodes, position information (longitude, latitude) for each node, an intersection identification flag for whether or not the node is an intersection, and if the node is an intersection, it indicates intersection data. If it is not an intersection, it is composed of a pointer or the like that points to the road link to which the node belongs.

The pendant control panel 2 joystick for relatively moving the vehicle position mark relative to the map, the angle correction key for setting the offset angle [theta] off, map search key, enlargement / reduction key, the optimum route search key and the like Equipped with various keys. As shown in FIG. 3, the GPS receiver 3 is a frequency conversion / amplifier 3 for converting the radio waves from the respective satellites received by the multi-beam antenna 4 into a predetermined intermediate frequency signal and amplifying it.
a, a receiver 3b that selects and detects a channel signal assigned to GPS from radio waves from each satellite, a decoder 3c that decodes the channel signal into digital data (time code data, etc.), and a processing unit 3d. I have it. Processing unit 3
Based on the decoded data, d performs three-dimensional positioning or two-dimensional positioning processing to calculate the vehicle position, azimuth, and vehicle speed, and outputs it in combination with the positioning time. The azimuth is the direction connecting the current vehicle position and the vehicle position one sampling time ΔT before, and the vehicle speed is the distance between the current vehicle position and the vehicle position one sampling time ΔT ago divided by the sampling time.

System Controller The system controller 6 includes a map data buffer memory 6a for temporarily storing map data, a map read control unit 6b, a vehicle position based on the self-contained navigation sensor output,
A vehicle position / azimuth calculation unit 6c that calculates a sensor azimuth, a vehicle position correction unit 6d that corrects the vehicle position, a vehicle position mark generation unit 6e, and a map drawing control that causes a map around the vehicle position to be displayed on the display device 7 together with the vehicle position mark. It has a portion 6f. The map read control unit 6b receives the current vehicle position and sends the map data corresponding to the current vehicle position to the CD-
Map data buffer memory 6a read from ROM1
Remember. The vehicle position / azimuth calculation unit 6c includes the angle sensor 5
The vehicle current position and the sensor azimuth are calculated by the equations (1) to (3) based on the output of the distance a and the distance sensor 5b.

The vehicle position correction unit 6d includes a traveling locus storage unit 6d-1 for storing the vehicle position and the sensor azimuth as a traveling locus at predetermined time intervals or predetermined distances, and a GP from the GPS receiver.
Each time the S azimuth is input, the GPS azimuth θgi, the sensor azimuth θsi at that time, the positioning time Ti, and the azimuth data storage unit 6d-2 that stores the latest offset angle θoff, and the map matching processing unit 6d-3 are included. ing. The map matching processing unit 6d-3 performs the map matching process using the road data and the traveling locus data read out to the map data buffer memory 6a, and when the map matching becomes impossible, the azimuth data storage unit 6d- The offset angle, that is, the absolute traveling azimuth is corrected using the azimuth data stored in 2. FIG. 4 shows the azimuth data storage unit 6d
It is an explanatory diagram of -2, and azimuth data (GPS azimuth θgi, sensor azimuth θsi, positioning time Ti) and the latest offset angle θoff are stored. The positioning time is G
It is included in the data from the PS receiver. The initial value of the offset angle θoff is set by the method shown in FIG.

The vehicle position mark generator 6e receives the vehicle position data and the traveling locus data and generates a traveling locus and a vehicle position mark. The map drawing control unit 6f reads the map data and traveling locus data around the current vehicle position from the map buffer memory 6a and the vehicle position mark generating unit 6e and inputs them to the display device 7. Display Device The display device 7 includes a CRT controller 8, a video RAM (V-RAM) 9, a read control unit 10, and a CRT.
11 and the like, and displays a desired map and vehicle position mark on the CRT screen (screen).

Overall Operation FIGS. 5 and 6 are flowcharts of the map matching process including the offset angle correction process of the present invention. The initial offset angle θoff is set by the method shown in FIG. If the GPS receiver 3 can perform positioning by three-dimensional positioning or two-dimensional positioning, it inputs the measured position data, azimuth data (GPS azimuth) θgi, positioning time Ti, etc. to the vehicle position correcting unit 6d. Also, the vehicle position / azimuth calculation unit 6c
Uses the outputs of the angle sensor 5a and the distance sensor 5b,
The current position of the vehicle and the traveling azimuth (sensor azimuth) θsi are calculated at predetermined time intervals and input to the vehicle position correction unit 6d. When the vehicle position correction unit 6d receives the GPS data (step 101), the GPS direction θgi and the sensor direction θsi at that time are received.
And the positioning time Ti is stored in the azimuth data storage unit 6d-2 (step 102). Further, the vehicle position correction unit 6d sequentially stores the vehicle position and the sensor orientation θsi input from the vehicle position / azimuth calculation unit 6d in the traveling locus storage unit 6d-1 (step 1
03).

The map matching processing section 6d-3 judges whether map matching processing is necessary (step 10).
4) If there is no need, the process returns to step 101 to repeat the process of storing the azimuth data and the traveling locus. On the other hand, if map matching is necessary, it is determined whether map matching is possible (step 105). If map matching is possible, the current vehicle position is corrected by the method described above, and the corrected value is input to the vehicle position / azimuth calculation unit 6c and the vehicle position mark generation unit 6e (step 106). The vehicle position mark generation unit 6e generates a vehicle position mark so as to be displayed on the corrected current vehicle position, and the map drawing control unit 6f reads the vehicle position mark data from the vehicle position mark generation unit 6e to display the display device 7 To display the corrected position on the map (step 107). After that, the process returns to the beginning and the process is repeated. The vehicle position / azimuth calculation unit 6c calculates the position data and the sensor azimuth according to the following equations (1) to (3) based on the corrected current vehicle position.

On the other hand, if the vehicle position calculated by the vehicle position / azimuth calculation unit 6d deviates significantly from the actual traveling road and map matching becomes impossible, "NO" is determined in step 105. In this case, the map matching processing unit 6d-3 refers to the time data Ti and determines whether or not there are n or more data items within the set time Tth from the current time in the azimuth data storage unit 6d-2 (step 108). If n or more exist, the latest n GPS orientation θgi, sensor orientation θ
Using si (i = 1,2, ... n) and the current offset angle θoff, the following equation θc = (1 / n) · Σ {θgi− (θsi + θoff)} (i = 1,2, ... n ) From (7), GPS direction θgi and absolute traveling direction (θsi + θoff)
The average value θc of the difference between and is calculated. Further, using the average value θc, the offset angle θoff so far is corrected by the following equation θoff + θc → θoff (8) (step 109). Next, the current vehicle position is corrected based on the position data input from the GPS receiver 3, and the corrected current vehicle position is input to the vehicle position / azimuth calculation unit 6c and the vehicle position mark generation unit 6e (step 110). .

The vehicle position mark generator 6e generates a vehicle position mark so that it is displayed on the corrected current vehicle position, and the map drawing controller 6f reads the vehicle position mark data from the vehicle position mark generator 6e. Input on the display device 7 and display at the corrected position on the map (step 1
11). After that, the process returns to the beginning and the process is repeated. On the other hand, in step 108, if there are no more than n azimuth data, in other words, if there are only m (<n) data, then the m GPS azimuths θgi and sensor azimuths θsi (i = 1,2). ,
... m) and the current offset angle θoff are stored in the azimuth data storage unit 6
It is read from d-2 (step 112), and the GPS azimuth θgi and absolute are obtained by the following equation θc = (1 / m) · Σ {θgi− (θsi + θoff)} (i = 1,2, ... m) (9) Driving direction (θsi + θoff)
The average value θc of the difference between and is calculated. Also, the average offset angle θc is used to correct the offset angle θoff so far according to equation (8).
(Step 113). Then, the processing from step 110 onward is performed. After that, using the new offset angle θoff obtained from Eq. (8) and the sensor azimuth θsi calculated from Eq. (1), the absolute running azimuth θai is calculated from the following equation θsi + θoff → θai (10), and (2) The vehicle position is calculated from equation (3). In step 108, "N
When it becomes “O”, the process of step 110 may be immediately performed without performing any steps in steps 112 and 113. This is because when the GPS direction contains a lot of errors (for example,
This is because there is a case where the number of data m = 1 and the GPS azimuth error is from 10 ^{0 to} 20 ⁰ ). Therefore, only position correction is performed and angle correction is not performed (θoff remains as it is).

(B) Second Embodiment of the Present Invention FIG. 7 shows a second embodiment of the present invention. The difference from the first embodiment of FIG. The azimuth data is stored in the azimuth data storage unit 6d-2 only when the condition is satisfied. The azimuth data storage determination unit 6g receives various data from the GPS receiver 3, the angle sensor 5a, and the distance sensor 5b, and receives the following data ...
Judge whether the condition of is satisfied. That is, when GPS data is input, the angular velocity obtained from the angle sensor 5a is less than or equal to a set value (for example, 2 degrees / sec), or measured based on the vehicle speed Vgps measured by GPS and the output of the distance sensor 5b. It is determined whether the ratio η (= 100 · | Vgps-Vcs | / Vcs) of the difference of the determined vehicle speed Vcs to the vehicle speed is a set value, for example, 5% or less, or whether the vehicle speed Vcs is a set speed (for example, 20 km) or more. .

The save enable signal STE is generated only when all the above conditions are satisfied. The vehicle position correction unit 6d stores the bearing data (GPS bearing, sensor bearing, positioning time) in the bearing data storage unit 6d-2 only when the save enable signal STE is input. As a result, only the GPS bearing with a small error is stored, and (7), (8),
The correct offset angle θoff can be calculated using equation (9),
Further, the accuracy of the absolute traveling direction obtained by the equation (10) can be improved.

The reason why the error of the GPS bearing becomes smaller depending on the conditions of, is as follows. If the X- and Y-direction distances between the previous and present sampling points are ΔX and ΔY, the GPS azimuth is calculated by arctan (ΔY / ΔX). Therefore, if there is a curve between the previous sampling point and the current sampling point, a considerably large error will be included in the GPS bearing. Therefore, if the condition is added, only the GPS azimuth data having a small error can be stored in the azimuth data storage unit. If the speed difference is large, it is highly possible that the vehicle is located in a place where satellite radio waves are blocked, such as in a tunnel or building, or there is a switching of receiving satellites or switching of SA (Selectable Availability). The GPS data contains a considerable error. Therefore, if the condition is added, only the GPS azimuth data having a small error can be stored in the azimuth data storage unit. Further, when the vehicle speed is low, the GPS data contains a considerable error. Therefore, the GPS azimuth data having a small error can be stored in the azimuth data storage unit by adding the condition of. Although the present invention has been described above with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0027]

As described above, according to the present invention, the difference between the azimuth (sensor azimuth) measured by the angle sensor and the actual traveling azimuth of the vehicle is set as an offset angle, and thereafter, the offset angle is added to the sensor azimuth. Then, the traveling direction of the vehicle is calculated and the direction data (GP)
S direction) and direction data measured by the angle sensor (sensor direction) are stored together with the positioning time, and when map matching becomes impossible, a plurality of GPS directions within a preset time from the current time are stored. Since the offset angle is corrected using the sensor azimuth and the running azimuth of the vehicle is calculated using the new offset angle, the offset angle can be accurately calculated without using the old azimuth data of the predetermined time before the current time. It can be corrected, and as a result, the absolute traveling direction of the vehicle can be accurately calculated.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a navigation system according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of road layers in map information.

FIG. 3 is a configuration diagram of a GPS receiver.

FIG. 4 is an explanatory diagram of an azimuth data storage unit.

FIG. 5 is a flowchart (part 1) of map matching processing including offset angle correction processing.

FIG. 6 is a flowchart (part 2) of map matching processing including offset angle correction processing.

FIG. 7 is a configuration diagram of a navigation system according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of position and azimuth calculation by self-contained navigation.

FIG. 9 is an explanatory diagram of a vehicle position and offset angle setting method.

FIG. 10 is an explanatory diagram of map matching processing by a projection method.

[Explanation of symbols]

 3 ・ ・ GPS receiver 5a ・ ・ Angle sensor 5b ・ ・ Distance sensor 6c ・ ・ Vehicle position / direction calculation unit 6d ・ ・ Vehicle position correction unit 6d-1 6d-3 ... Map matching processing unit 7 ... Display device

Claims (1)

[Claims] 1. A map is drawn on a display screen based on map data, and the vehicle position and traveling direction are measured by self-contained navigation to display a vehicle position mark on the map. The navigation direction of the navigation device that corrects the vehicle position data as shown above and corrects the vehicle position and traveling direction data using the position data and direction data obtained from GPS when map matching becomes impossible. In the calculation method, the difference between the azimuth measured by the angle sensor (sensor azimuth) and the actual traveling azimuth of the vehicle is set as an offset angle, and then the offset azimuth is added to the sensor azimuth to calculate the traveling azimuth of the vehicle. At the same time, the azimuth measured by GPS (GPS azimuth) and the sensor azimuth measured by the angle sensor are measured. When the map matching becomes impossible, the offset angle is corrected using multiple sets of GPS direction and sensor direction within the preset time from the current time, and the new offset angle is used. A traveling direction calculation method characterized by calculating the traveling direction of a vehicle.