JPH04276516A - Vehicle mounted navigator - Google Patents

Abstract

PURPOSE:To decrease the errors in displays of vehicle position data such as positions of vehicles and running locus at places wherein map matching is not performed. CONSTITUTION:A primary-distance-correcting-coefficient determining part 6e obtains the primary-distance-correcting coefficient based on the ratio between the distances before and after the correction when the distance of the running locus is corrected with a map matching part 6d. A secondary-distance-correcting- coefficient determining part 6f obtains the secondary-distance correcting coefficient by sequentially multiplying the primary-distance correcting coefficient every time the first-distance correcting coefficient is obtained with the primary- distance-correcting coefficient determining part 6e. A vehicle-position computing CPU 15 corrects the error of the a distance sensor 4 by using the second- distance-correcting coefficient which is obtained with the secondary-distance- correcting-coefficient 6f and computes the present position of the vehicle.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an in-vehicle navigator.
In particular, the present invention relates to an in-vehicle navigator that corrects vehicle position information detected by self-contained navigation on a road using map matching processing.

0002

2. Description of the Related Art There is an in-vehicle navigator that provides driving guidance for a vehicle and allows the driver to easily reach a desired destination. In this in-vehicle navigator, the position of the vehicle is detected, map data around the vehicle position is read from the CD-ROM, a map image is drawn in the V-RAM, and a vehicle position mark is superimposed on the map image. - Converting the image in the RAM to a video signal and outputting it to the CRT display for display on the screen. Then, as the current position changes due to the movement of the vehicle, the vehicle position mark on the screen is moved, or the vehicle position mark is fixed at the center of the screen and the map is scrolled, so that the map around the vehicle position is always displayed. Information can be seen at a glance.

[0003] In the map data stored on the CD-ROM, roads are represented by a set of coordinates of vertices (nodes) expressed in latitude and longitude, and these drawings are performed by sequentially connecting each node with a straight line. . Note that a portion that connects two or more nodes is called a road link.

[0004] Incidentally, in a vehicle-mounted navigator that uses self-contained navigation, the vehicle position is detected by integrating the outputs of a distance sensor and a direction sensor. FIG. 8 is an explanatory diagram showing a vehicle position detection method using self-contained navigation. The distance sensor outputs a pulse every time the vehicle travels a certain unit distance s0, and the reference direction (θ=0) is set in the positive direction of the , Y0), the output of the orientation sensor at the time of traveling a unit distance s0 is θ1, and the output of the orientation sensor at the time of traveling a unit distance s0 is θ2, and so on, each time the unit distance s0 is traveled. The output of the direction sensor is θ3,...
・, θi, the position coordinates of point Pi (X,
Y) is X=X0 +s0 ・cos θ
1 +s0 ・cos θ2 +s0 ・cos θ3
+...+s0 ・cos θ
i
...(1) Y=Y0 +s0 ・s
in θ1 +s0 ・sin θ2 +s0 ・si
n θ3 +...+s0 ・s
in θi
...It can be calculated as (2).

However, there is an error in the distance sensor, and the distance s=
s0 ・Se (Se is the error coefficient) A pulse is output every time you drive, and the direction sensor also has an error, so the detected direction is +
When the vehicle is deviated by θe in the direction (when the detected orientation θ of the orientation sensor is θe when the vehicle is heading toward the reference orientation), the accurate vehicle position Pi ′(X′, Y
′) is X′=X0 +(s0 ・Se )・{cos
(θ1 - θe) + cos (θ2 - θe)
+cos (θ3 -θe)+...+c
os (θi −θe)} ...(3) Y'=
Y0 + (s0 ・Se ) ・{sin (θ1 −θ
e )+sin (θ2 −θe) +s
in (θ3 −θe )+...+sin (θi
−θe )} (4).

[0006] Therefore, the vehicle position can be simply calculated using equations (1) and (2).
) calculation results in an error in the vehicle position, and the error increases as the vehicle travels. For this reason, the detected vehicle position is compared with road data in map data and corrected on the road (map matching process). 9 to 11 are explanatory diagrams of map matching. When a vehicle heads north on road RDa, enters road RDb at the intersection of point Pa, heads east on the road, enters road RDc at the intersection of point Pb, and heads northeast to point Pc. Road RDa
The traveling trajectory RTDa when traveling on the road RDa has been corrected to be on the road RDa in the previous map matching, but the traveling trajectory RTDb0 when traveling on the road RDb changes from point Pa to point Pb0 due to errors in the distance sensor and direction sensor. Furthermore, the traveling trajectory RTDc0 when moving on the road RDc is from point Pb0 to P
It is assumed that the vehicle position mark CM is up to c0 (see FIG. 9, the vehicle position mark CM is displayed at point Pc0).

[0007] In pattern matching, the traveling trajectory RTD (RTDa, RTDb0, RTDc0) near the vehicle position is
), (1) Search for road paths RDa, RDb, RDc that have the same shape as the travel trajectory RTD using the road data, and (2
) In order to move all or part of the travel trajectory RTD and overlap it with the road paths RDa, RDb, RDc, reference points,
For example, focusing on the latest intersection Pb where the vehicle turned and the previous intersection Pa, point Pa is set so that the direction of the travel trajectory RTDb0 matches the direction of the road path RDb.
The traveling trajectories RTDb0 and RTDc0 are rotated integrally around , and the traveling trajectories RTDb1 and RTDc1 after rotation are
Then, find the points Pb1 and Pc1 (see Fig. 10), (3) Furthermore, the traveling trajectories RTDb1 and RTDc1 after rotation
In order to match road paths RDb and RDc, Pa
Reduce or expand the travel trajectory RTDb1 based on the point Pc1 to find the destination point Pc2 (see FIG. 11). (4) After that, change the travel trajectory display to RTDb0, RTDc.
While moving from 0 to RTDb2 and RTDc2,
Move the vehicle position mark display from Pc0 to Pc2 (
(See RTD', CM' in FIG. 11).

According to this map matching process, even if there is an error in the distance sensor or direction sensor, the vehicle position and travel trajectory can be corrected to the correct position.

[0009]

[Problems to be Solved by the Invention] However, the map matching process described above can only be executed when a road path with the same shape as the travel trajectory is found, and there may be multiple road paths with the same shape as the travel trajectory near the vehicle position. If the map matching process cannot be performed due to the presence of a vehicle, the incorrect vehicle position or travel trajectory will continue to be displayed due to errors in the distance sensor or direction sensor until the next map matching is performed.
Especially when the next map matching will not be done for a while,
There has been a problem in that errors in the distance sensor and direction sensor accumulate, causing the vehicle position and travel trajectory to deviate significantly from the original position.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an in-vehicle navigator that can reduce display errors in vehicle position information such as the vehicle position and travel trajectory while map matching is not performed.

[0011]

[Means for Solving the Problems] The above-mentioned problem is solved in one aspect of the present invention by a vehicle position detection means that includes a map data storage means storing map data, a distance sensor and a direction sensor, and detects the current position of the vehicle. a travel trajectory storage means for storing a travel trajectory indicated by a change in the vehicle position; a correction means for correcting the travel trajectory stored in the travel trajectory storage means by comparing it with road data stored in the map data storage means; In an in-vehicle navigator equipped with a map drawing control means for displaying vehicle position information on a display means together with a map around the vehicle position based on the corrected travel trajectory, when the distance of the travel trajectory is corrected by the correction means, the distance before and after the correction is A primary distance correction coefficient determining means calculates a primary distance correction coefficient from the ratio of This is achieved by providing a secondary distance correction coefficient determining means for determining the distance, and detecting the current position by correcting the error of the distance sensor based on the secondary distance correction coefficient.

In another aspect of the present invention, when the azimuth of the travel trajectory is corrected by the correction means, a primary azimuth correction amount determining means for determining a primary azimuth correction amount from the difference between the azimuths before and after the correction; Each time the primary azimuth correction amount is determined by the correction amount determination means, a secondary azimuth correction amount determining means is provided for adding the primary azimuth correction amount to obtain a secondary azimuth correction amount,
The current position detection means is achieved by detecting the current position by correcting the error of the orientation sensor based on the secondary orientation correction amount.

[0013]

[Operation] According to one aspect of the present invention, when the distance of the travel trajectory is corrected by the correction means, a primary distance correction coefficient is obtained from the ratio of the distances before and after correction, and the primary distance correction coefficient is further multiplied one after another. A secondary distance correction coefficient is obtained, and the error of the distance sensor is corrected based on the secondary distance correction coefficient to detect the current position. As a result, even if there is an error in the distance sensor, the vehicle position can be detected while correcting it, which reduces the display error of the vehicle position and driving trajectory between map matching and the next map matching. Since more accurate correction becomes possible each time map matching is repeated, display errors in the vehicle position and travel trajectory gradually become smaller as the vehicle travels.

According to another aspect of the present invention, when the direction of the travel trajectory is corrected by the correction means, a primary direction correction amount is obtained from the difference between the direction before and after the correction, and further, the primary direction correction amount is A secondary azimuth correction amount is determined by sequential addition, and the error of the azimuth sensor is corrected based on the secondary azimuth correction amount to detect the current position. As a result, even if there is an error in the direction sensor, the vehicle position can be detected while correcting it, reducing the display error of the vehicle position and driving trajectory between map matching and the next map matching. Since more accurate correction becomes possible each time map matching is repeated, display errors in the vehicle position and travel trajectory gradually become smaller as the vehicle travels.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of the main parts of an on-vehicle navigator according to the present invention.

In the figure, 1 is a CD-ROM serving as a map data storage means, 2 is an operation panel, and includes left, right, up, and down scroll keys for scrolling the map with respect to the vehicle position mark, map search, It is equipped with various keys for enlarging/reducing. Reference numeral 3 denotes a direction sensor that detects the direction in which the vehicle is traveling as viewed from a predetermined reference direction and outputs a direction signal, 4 a distance sensor that outputs a pulse indicating that the vehicle has traveled a certain distance every time it travels a certain distance s, and 5 a direction sensor that outputs a pulse indicating that the vehicle has traveled a certain distance. A CPU for calculating the vehicle position using autonomous navigation calculates the current position (longitude, latitude) of the vehicle by integrating signals input from the direction sensor 3 and distance sensor 4 from the starting point.

However, the direction sensor 3 has an offset error θe
It is also assumed that the distance sensor 4 has a set unit distance of s0, and outputs a pulse every time it travels: s=s0.Se (Se is an error coefficient). The vehicle position calculation CPU 5 corrects the error of the azimuth sensor 3 based on the secondary azimuth correction amount θc2 inputted from the secondary azimuth correction amount determining section, which will be described later, and also corrects the error of the azimuth sensor 3 based on the secondary azimuth correction amount θc2 inputted from the secondary azimuth correction amount determining section, which will be described later. The vehicle position is detected by correcting the error of the distance sensor 4 based on the correction coefficient Sc2.

Reference numeral 6 denotes a system controller composed of a microcomputer, which causes a map around the vehicle position to be displayed on a display device, which will be described later, together with a traveling trajectory and a vehicle position mark. 6a is a map data buffer memory; 6b is a CD-ROM that inputs vehicle position data from the CPU 5 for calculating vehicle position;
1 to a map readout control unit that reads out map data around the vehicle position to the map data buffer memory 6a; 6c is a travel trajectory storage unit that stores changes in the vehicle position data input from the vehicle position calculation CPU 5 as a travel trajectory; 6d;
compares the shape of the travel trajectory stored in the travel trajectory storage unit 6c with the road data in the map data read out to the map data buffer memory 6a, searches for road paths with the same shape, and corrects the travel trajectory and vehicle position. The map matching unit 6e is a primary distance correction coefficient determination unit 6f that calculates a primary distance correction coefficient SC1 from the ratio of the distance before and after correction when the distance of a straight line section of a certain distance or more is corrected by the map matching unit 6d.
6g is a secondary distance correction coefficient determination unit that sequentially multiplies to obtain a secondary distance correction coefficient every time the primary distance correction coefficient SC1 is determined, and 6g is a map matching unit 6d that corrects the orientation of a straight section over a certain distance. 6h, a primary azimuth correction amount determination unit that calculates a primary azimuth correction amount from the difference between the azimuths before and after the correction;
6i is a secondary azimuth correction amount determination unit that sequentially adds the primary azimuth correction amount to obtain a secondary azimuth correction amount every time the primary azimuth correction amount is determined; 6i reads out map data around the vehicle position from the map data buffer memory 6a and sends it to the display device. This is a map drawing control section that outputs and draws a map, reads travel trajectory data and vehicle position data from the travel trajectory storage section 6c, outputs them to a display device, and displays the travel trajectory and vehicle position mark.

A display device 10 includes a CRT controller 11, a video RAM (V-RAM) 12, a readout control section 13, a CRT 14, etc., and is configured to display desired maps and marks on the CRT screen. .

FIG. 2 is a flow chart showing the vehicle position calculation process of the vehicle position calculation CPU 5, and FIG.
4 to 7 are flowcharts showing the map and mark drawing process, the map matching process, and the correction data determination process for the distance sensor and direction sensor, and FIGS. 4 to 7 are explanatory diagrams of the map matching method, and the following description will be made with reference to these figures.

[0021] In addition, in accordance with the driver's map selection operation, the map reading control unit 6b transfers map data of a predetermined scale including the departure point from the CD-ROM 1 to the map data buffer memory 6a, and performs map drawing control. The section 6i reads map data from the map data buffer memory 6a, outputs it to the display device 10, and displays the desired map on the CRT 1.
Assume that the image is drawn on screen 4.

[0022] When the driver performs an operation to set the departure point on the operation panel 2, the position coordinates (X0, Y0) of the departure point P0 become (
X, Y) in the vehicle position calculation CPU 5 (step 101 in FIG. 2). During this initial setting process,
The vehicle position calculation CPU 5 sets the secondary distance correction coefficient Sc2' to 1 and the secondary azimuth correction amount θc2' to 0. Further, the positional coordinates (X0, Y0) of the starting point P0 are registered in the traveling trajectory storage unit 6c of the system controller 6, and the map drawing control unit 6i uses the positional coordinates of the starting point as vehicle position mark data on the display device 10. Output to
A vehicle position mark CM is displayed at a predetermined location on the map screen (steps 201 to 203 in FIG. 3). At this time, the secondary distance correction coefficient determination unit 6f of the system controller 6 sets the secondary distance correction coefficient Sc2 to 1, and the secondary azimuth correction amount determination unit 6h sets the secondary azimuth correction amount θc2 to 0 (step 20
4).

When the vehicle starts traveling, the distance sensor 4 outputs a pulse every time the vehicle travels a certain distance s. Every time a pulse is input from the distance sensor 4, the vehicle position calculation CPU
5 inputs the orientation signal θ from the orientation sensor 3, and uses the set unit distance s0, the secondary distance correction coefficient Sc2', the detected orientation θ, and the secondary orientation correction amount θc2', and calculates Δx=(s0 ・Sc2
′)・cos(θ−θc2′) ...(4)
Δy=(s0 ・Sc2
′)・sin(θ−θc2′) ...(5)
X=X+Δx

...(6)
Y=Y+Δy
... Performs the calculation in (7) to obtain a new vehicle position (X, Y), and outputs the vehicle position data to the system controller 6 (steps 103-
106).

However, there is an error in the output of the distance sensor 4, and the distance sensor 4 outputs a pulse every time it travels s = s0 ・Se, and there is an error in the output of the direction sensor 3, so it is offset by θe in the + direction. When an error occurs, initially Sc2' = 1 and θc2' = 0, and since no correction is made for the error of the distance sensor 4 and the error of the direction sensor 3, the vehicle position calculation CPU 5 outputs The error in the position data gradually increases.

Based on the vehicle position data inputted from the vehicle position calculation CPU 5, the map readout control unit 6b of the system controller 6 determines whether the vehicle has moved out of the range of the map that has been read out to the map data buffer memory 6a.
When the vehicle is removed, the new map data containing the vehicle position is stored on the CD-
The map data is read from the ROM 1 to the map data buffer memory 6a. Further, the traveling trajectory storage unit 6c is a CPU for calculating the vehicle position.
The map drawing control section 6i outputs the traveling trajectory data stored in the traveling trajectory storage section 6c to the display device 10. While displaying the traveling trajectory RTD, the position data of the final end of the traveling trajectory stored in the traveling trajectory storage section 6c is outputted to the display device 10 as vehicle position mark data, and the vehicle position mark CM on the map screen is moved. In addition, the map drawing control unit 6
When the vehicle position is off the screen, i reads map data for one screen containing the new vehicle position from the map data buffer memory 6a and outputs it to the display device 10 to change the displayed map (hereinafter referred to as navigation). process,
Step 205).

When the map matching becomes possible due to the vehicle turning at an intersection (YES in step 206, see FIG. 4), the map matching unit 6d first performs the following steps.
Comparing the shape of the road data stored in the map data buffer memory 6a and the travel trajectory RTD, a road path RD having the same shape is determined.
A and RDB are searched for (step 207), and then movement is performed so that the travel trajectory RTD overlaps the road paths RDA and RDB (step 208). Here, we focus on the latest intersection PB where the vehicle turned and the departure point P0,
The traveling trajectory R is centered around point P0 so that the direction of the traveling trajectory RTDA0 matches the direction of the road path RDA.
Rotate TDA0 and RTDB0 integrally to RT the travel trajectory
Modify to DA1 and RTDB1. At this time, point P
B0 moves to PB1, and point PC0 moves to PC1 (see FIG. 5).

When performing this movement correction, the map matching section 6d measures the length of the rotating travel trajectory RTDA0, examines the change in angle along the way, and calculates the length of the rotated travel trajectory RTDA0.
Determine whether A0 is a straight section of a certain distance or more (step 20
9) If YES, output the azimuth of the original traveling trajectory RTDA0 as θA and the azimuth of the corrected traveling trajectory RTDA1 (azimuth of the road path RDA) as θB to the primary azimuth correction amount determination unit 6g. The primary azimuth correction amount determination unit 6g that has input θA and θB calculates θC1 = θA - θB to obtain the primary azimuth correction amount θC1, and calculates the primary azimuth correction amount θC.
1 to the secondary azimuth correction amount determination unit 6h (step 2
10).

The secondary azimuth correction amount determination unit 6h which has input the primary azimuth correction amount θC1 calculates the secondary azimuth correction amount θC2 by adding θC2=θC2+θC1, and calculates the secondary azimuth correction amount θC2.
Output to PU5 (steps 211, 212). When the vehicle position calculation CPU 5 inputs the secondary azimuth correction amount θC2, the CPU 5 calculates the secondary azimuth correction amount θ that has been used for calculating the vehicle position.
Replace C2' (=0) with the secondary azimuth correction amount θC2 (
Steps 107, 108 in FIG. 2).

Next, the map matching section 6d performs P0
Based on , the traveling trajectory RTDA1 is reduced or enlarged so that the point PB1 coincides with PB, and the traveling trajectory RT
The route is corrected to DA2, and the travel trajectory RTDB1 is accordingly moved to RTDB2 (step 213). At this time,
Point PC1 moves to PC2 (see FIG. 6).

When performing this enlargement/reduction correction, the map matching section 6d determines whether the travel trajectory RTDA1 whose distance has been corrected is a straight section of a certain distance or more (step 214),
When YES, the distance of the original travel trajectory RTDA1 is LA.
, outputs the distance of the corrected travel trajectory RTDA2 as LB to the primary distance correction coefficient determination unit 6e. LA and LB
The primary distance correction coefficient determination unit 6e inputs SC1=LB.
/LA is calculated to obtain a primary distance correction coefficient SC1, and the primary distance correction coefficient SC1 is output to the secondary distance correction coefficient determination unit 6f (step 215).

The secondary distance correction coefficient determining unit 6f which has input the primary distance correction coefficient SC1 calculates the secondary distance correction coefficient SC2 by multiplying SC2=SC2·SC1 and outputs it to the vehicle position calculation CPU 5 (step 216, 217). When the vehicle position calculation CPU 5 inputs the secondary distance correction coefficient SC2, it replaces the secondary distance correction coefficient SC2' (=1) that had been used for calculating the vehicle position with the secondary distance correction coefficient SC2 (steps in FIG. 2). 109, 110).

[0032] Once the travel trajectory has been corrected in this way,
The map matching unit 6d uses the corrected position data of point Pc2 as corrected vehicle position data and uses C for vehicle position calculation.
Output to PU5 (step 218). Further, the map drawing control unit 6i outputs the corrected driving trajectory data stored in the driving trajectory storage unit 6c to the display device 10 to correct the display of the driving trajectory RTD to RTD′, and displays the corrected driving trajectory. The position data of the final end PC2 is outputted as vehicle position mark data to the display device 10, and the display of the vehicle position mark CM is changed to CM' (step 219).
, see Figure 6). The system controller 6 then returns to step 205 and performs the navigation processing described above.

The vehicle position calculation CPU 5 that has received the corrected vehicle position data changes the vehicle position coordinates (X, Y), and thereafter calculates the vehicle position using the changed vehicle position as a new starting point (see FIG. 2). Steps 111, 112). On this occasion,
Since the secondary azimuth correction amount θc2' and the secondary distance correction coefficient SC2' have been replaced, the vehicle position calculation CPU 5
According to equations (4) to (7), the offset azimuth error occurring in the output of the azimuth sensor 3 is corrected, and the set unit distance s0 occurring in the output of the distance sensor 4 and the actual unit traveling distance s (= s0 The vehicle position is calculated by correcting the error in ・Se ), which reduces the error in the vehicle position.

[0034] Therefore, when the primary azimuth correction amount and the primary distance correction coefficient can be calculated during map matching, the travel trajectory display and vehicle position displayed on the screen will be The error in mark display becomes smaller than before map matching.

[0035] After that, when the second intersection PD is turned and the second map matching becomes possible (see Fig. 7).
, the system controller 6 now corrects the movement and enlarges/reduces the traveling trajectory RTD based on PB to correct the traveling trajectory so that PD0 coincides with PD,
In addition to correcting the display of the driving trajectory and vehicle position mark,
If the original travel trajectory RTDC0 is a straight section of a certain distance or more, the primary azimuth correction amount determination unit 6g and the primary distance correction coefficient determination unit 6e calculate the primary azimuth correction amount θC1 and the primary distance correction coefficient Sc1 in the same manner as described above. . The primary azimuth correction amount θC1 and the primary distance correction coefficient Sc1 obtained at this time cannot be corrected by the secondary azimuth correction amount θC2 and the secondary distance correction coefficient Sc2 obtained during the first map matching, but it is still not possible to accurately calculate the vehicle position. This is the re-correction value that is necessary when there is no correction.

[0036] Then, the secondary azimuth correction amount determining unit 6h adds the newly obtained primary azimuth correction amount θC1 to the previous secondary azimuth correction amount θc2 to obtain a new, more appropriate secondary azimuth correction. In addition to determining the amount θC2, the secondary distance correction coefficient determination unit 6f also calculates the newly determined primary distance correction coefficient S.
A new, more appropriate secondary distance correction coefficient Sc2 is obtained by multiplying c1 by the previous secondary distance correction coefficient Sc2.

Then, the newly determined secondary azimuth correction amount θC
2 and the secondary distance correction coefficient Sc2, the vehicle position calculation CPU
5 replaces the secondary azimuth correction amount θC2' and the secondary distance correction coefficient Sc2' used for calculating the vehicle position. This results in
The vehicle position data calculated after the second map matching becomes more accurate, and the traveling trajectory display and vehicle position mark display also become more accurate.

Hereinafter, in the same way, when the traveling trajectory of a straight section of a certain distance or more is corrected by map matching, the CPU 5 for calculating the vehicle position calculates the secondary azimuth correction amount θC2' and the secondary Since the distance correction coefficient Sc2' is corrected to a more appropriate value, each time the vehicle travels and map matching is repeated, the traveling trajectory display and vehicle position mark display will gradually become more accurate until the next map matching. To go.

In the above embodiment, both the error of the direction sensor and the error of the distance sensor are corrected, but only one of them may be corrected. In addition, although the CPU for calculating the vehicle position corrects the error between the direction sensor and the distance sensor, a secondary direction correction amount θC2 is given to the direction sensor, and the secondary direction correction amount θ is calculated from the detected direction θ within the direction sensor.
The error of the direction sensor may be corrected by subtracting C2 and outputting the result to the vehicle position calculation CPU.Also, when the distance sensor has counted a set number of wheel speed pulses, When configured to output a pulse indicating that the vehicle has traveled, a secondary distance correction coefficient Sc2 is applied to the distance sensor.
The error of the distance sensor may be corrected by giving the following value and changing the set number according to the secondary distance correction coefficient Sc2.

Furthermore, when starting up the in-vehicle navigator system, the secondary distance correction coefficient SC2' = 1 and the secondary azimuth correction coefficient θC2' = 0 were initially set (see step 102 in Fig. 2). When the system is started up, the secondary distance correction coefficient SC2' and the secondary azimuth correction coefficient θC2' at that time are backed up in memory, and when the next system is started up, the secondary distance correction coefficient SC2' is set using the backup data. The secondary azimuth correction coefficient θC2' may be initialized as follows.

[0041]

According to one aspect of the present invention, when the distance of the travel trajectory is corrected by the correction means, a primary distance correction coefficient is determined from the ratio of the distance before and after the correction, and further, the primary distance correction coefficient is Since the configuration is configured to calculate the secondary distance correction coefficient by successive multiplication, correct the error of the distance sensor based on the secondary distance correction coefficient, and detect the current position, even if there is an error in the distance sensor, it can be corrected. Since the vehicle position can be detected while the map is being matched, the display error of the vehicle position and driving trajectory from map matching to the next map matching is reduced, and moreover, it is possible to make more accurate corrections each time map matching is repeated. Therefore, as the vehicle travels, the display errors in the vehicle position and travel trajectory gradually become smaller.

According to another aspect of the present invention, when the direction of the travel trajectory is corrected by the correcting means, the primary direction correction amount is determined from the difference between the direction before and after the correction, and further, the primary direction correction amount is Since the configuration is configured such that the secondary azimuth correction amount is determined by sequential addition, and the current position is detected by correcting the error of the azimuth sensor based on the secondary azimuth correction amount, even if there is an error in the azimuth sensor, it can be corrected. Since the vehicle position can be detected while the map is being matched, the display error of the vehicle position and driving trajectory from map matching to the next map matching is reduced, and moreover, it is possible to make more accurate corrections each time map matching is repeated. Therefore, as the vehicle travels, the display errors in the vehicle position and travel trajectory gradually become smaller.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts of an in-vehicle navigator according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the vehicle position calculation CPU in FIG. 1;

FIG. 3 is a flowchart showing the operation of the system controller of FIG. 1;

FIG. 4 is an explanatory diagram of a map matching method in the in-vehicle navigator of FIG. 1;

FIG. 5 is an explanatory diagram of a map matching method in the in-vehicle navigator of FIG. 1;

FIG. 6 is an explanatory diagram of a map matching method in the in-vehicle navigator of FIG. 1;

7 is an explanatory diagram of a map matching method in the in-vehicle navigator of FIG. 1. FIG.

FIG. 8 is an explanatory diagram of a general vehicle position detection method using self-contained navigation.

FIG. 9 is an explanatory diagram of a general map matching method in an in-vehicle navigator.

FIG. 10 is an explanatory diagram of a general map matching method in an in-vehicle navigator.

FIG. 11 is an explanatory diagram of a general map matching method in an in-vehicle navigator.

[Explanation of symbols]

1 CD-ROM 3 Direction sensor 4 Distance sensor 5 CPU for vehicle position calculation 6 System controller 6c　Travel trajectory storage section 6d Map matching part 6e Primary distance correction coefficient determination unit 6f Secondary distance correction coefficient determination unit 6g Primary azimuth correction amount determination unit 6h Secondary azimuth correction amount determination unit 6i Map drawing control section 10 Display device

Claims (2)

[Claims] 1. A map data storage means that stores map data; a vehicle position detection means that includes a distance sensor and a direction sensor and detects the current position of the vehicle; and a travel trajectory that stores a travel trajectory indicated by a change in the vehicle position. a storage means; a correction means for correcting the travel trajectory stored in the travel trajectory storage means by comparing it with road data stored in the map data storage means; In an in-vehicle navigator equipped with a map drawing control means for displaying on a display means together with a map, when the distance of a traveling trajectory is corrected by the correction means, a primary distance correction coefficient determination means for determining a primary distance correction coefficient from a ratio of the distance before and after the correction. Each time a primary distance correction coefficient is determined by the primary distance correction coefficient determination means, a secondary distance correction coefficient determination means is provided which sequentially multiplies the primary distance correction coefficient to obtain a secondary distance correction coefficient. An in-vehicle navigator characterized in that the detection means detects the current position by correcting the error of the distance sensor based on a secondary distance correction coefficient. 2. Map data storage means that stores map data; vehicle position detection means that includes a distance sensor and a direction sensor and detects the current position of the vehicle; and a travel trajectory that stores a travel trajectory indicated by a change in the vehicle position. a storage means; a correction means for correcting the travel trajectory stored in the travel trajectory storage means by comparing it with road data stored in the map data storage means; In an in-vehicle navigator equipped with a map drawing control means for displaying on a display means together with a map, when the direction of a travel trajectory is corrected by the correction means, a primary direction correction amount determining means for determining a primary direction correction amount from the difference between the direction before and after the correction. And each time the primary azimuth correction amount is determined by the primary azimuth correction amount determining means,
A secondary azimuth correction amount determination means is provided to sequentially add the primary azimuth correction amount to obtain a secondary azimuth correction amount, and the current position detection means corrects the error of the azimuth sensor based on the secondary azimuth correction amount. An in-vehicle navigator characterized by detecting the current position.