JP2612765B2 - In-vehicle navigation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an in-vehicle navigation device, and more particularly to a GPS (Global Positioning System) that outputs coordinate data representing an absolute position of a vehicle.
Positioning System) The present invention relates to an in-vehicle navigation device including a receiver.

BACKGROUND ART In recent years, map data including road data obtained by digitizing each point on a road segment of a map is stored in a recording medium such as a CD-ROM, and the current position of the vehicle is included while confirming the current position of the vehicle. An in-vehicle navigation device has been developed that reads a map data group of a certain range of areas from a storage medium and projects it on a display as a map around the current position of the vehicle on a display, and automatically displays the own vehicle position indicating the current position of the vehicle on the map, It is being put to practical use.

Such an in-vehicle navigation device has a configuration in which the direction of travel of a vehicle is obtained by a direction sensor and the distance of travel of the vehicle is obtained by a distance sensor, and the current position of the vehicle on a map is estimated from the direction of travel and the distance of travel. Here, both the azimuth data and the distance data obtained by the azimuth sensor and the distance sensor usually include an error of about several percent, so that the current position of the vehicle to be inferred from these data necessarily corresponds to the actual traveling position. It will have an error.

According to the longitude and latitude information obtained from the output data of the GPS receiver (hereinafter referred to as GPS data), the absolute position can be estimated with a certain degree of accuracy. An in-vehicle navigation device for estimating the current location has also been developed. In this in-vehicle navigation device, the reception of radio waves from artificial satellites by the GPS receiver is performed at time intervals of about several seconds, and therefore, it is also conceivable to perform interpolation using the sensor data of the direction sensor and the distance sensor.

However, as the receiving position of the GPS receiver moves as the vehicle travels, for example, the positional relationship of the satellites that can be received may not be sufficient, or radio waves may not be received from a sufficient number of satellites. In such a case, the accuracy of the GPS data may be deteriorated. If the accuracy of the GPS data is poor or the accuracy of the map data is not sufficient, the estimated current position of the vehicle will be displayed off the road on the display, giving the user a sense of discomfort.

[Summary of the Invention] [Object of the Invention] Accordingly, the present invention provides a method for reducing the accuracy of GPS data,
It is an object of the present invention to provide an in-vehicle navigation device capable of displaying the current location of a vehicle on a map without discomfort even when the accuracy of the map data is not sufficient.

[Invention Configuration] An on-vehicle navigation device according to the present invention includes a GPS receiver that outputs coordinate data representing an absolute position of a vehicle, a plurality of road data including road data obtained by digitizing each point on a road segment of a map. Reading means for reading a map data group from a storage medium in which a plurality of map data groups respectively corresponding to the areas are stored, and while recognizing the current location of the vehicle based on the GPS data, An in-vehicle navigation device configured to extract a map data group from a storage medium and display a map around the current location and the current location on a display unit, wherein a difference between a current value and a previous value of longitude and latitude information obtained from GPS data is provided. And the coordinate data obtained by adding the difference to the coordinate data of the previously determined current position is used as the estimated current position, and the road line segments near the estimated current position are displayed. A set of road segment data is searched from the map data, and the coordinate data is corrected by the searched set of road segment data so that the estimated current position is located on the represented road segment, and the corrected current position is determined. Of the coordinate data.

[Operation of the Invention] In the vehicle-mounted navigation device according to the present invention, the GP
While recognizing the current location of the vehicle based on the S data, a map data group of a certain range including the current location is extracted from the storage medium, and a map around the current location of the vehicle and the current location are displayed on the display unit, and the GPS data The difference between the current value and the previous value of the longitude and latitude information obtained from is calculated, and the difference is added to the coordinate data of the previously determined current position to obtain coordinate data obtained as the estimated current position. A road segment data group representing a minute is searched from the map data, and the coordinate data is corrected by using the searched road segment data group so that the estimated current position is located on the represented road segment. The coordinate data of the determined current location is used.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a vehicle-mounted navigation device according to the present invention. In the figure, reference numeral 1 denotes an azimuth sensor for detecting a traveling azimuth of a vehicle, 2 denotes an angular velocity sensor for detecting an angular velocity of the vehicle, 3 denotes a distance sensor for detecting a traveling distance of the vehicle, and 4 denotes latitude and longitude information. It is a GPS receiver for detecting the absolute position of the vehicle from the above, etc., and the detection output of each of these sensors (hereinafter, referred to as a GPS receiver) is supplied to the system controller 5. As the direction sensor 1, for example, a geomagnetic sensor that detects the running direction of the vehicle based on geomagnetism is used.

The system controller 5 receives an output of each of the sensors 1 to 4 as an input and performs an A / D (analog / digital) conversion process and the like. CPU (Central Processing Circuit) 7 for calculating the traveling distance, traveling direction, current position coordinates (longitude, latitude), etc. of the vehicle based on the output data of the sensors 1 to 4, various processing programs of the CPU 7, and other necessary Information is pre-written
A ROM (read only memory) 8 and writing and reading of information necessary for executing a program are performed.
And a RAM (random access memory) 8.

As the external storage medium, for example, a CD-ROM as a read-only nonvolatile storage medium and a DAT (Digital Audio Tape) as a writable and readable nonvolatile storage medium are used. The external storage medium is not limited to a CD-ROM or DAT, but may be a non-volatile storage medium such as an IC card. CD-ROM
Stores in advance map data obtained by digitizing (digitizing) each point on the road of the map. This CD-
The stored information is read from the ROM by the CD-ROM driver 10. The read output of the CD-ROM driver 10 is decoded by the CD-ROM decoder 11 and sent out to the bus line L.

On the other hand, DAT is used as a so-called backup memory, and information recording or reading is performed on the DAT deck 1.
Done by two. When the vehicle power is turned off, information such as the current location coordinates of the vehicle stored in the RAM 9 immediately before that is supplied to the DAT deck 12 via the DAT encoder / decoder 13 as backup data, and is stored in the DAT. DAT memory information is stored in the DAT deck when the
Read by 12. The read information is transmitted to the bus line L via the DAT encoder / decoder 13 and stored in the RAM 9.

The turning on and off of the vehicle power is detected by a detection circuit 14 that monitors the output level of a so-called accessory switch SW of the vehicle. Vehicle power from a battery (not shown) via the accessory switch SW is stabilized by the regulator 15 and supplied as power to each unit of the device.
The output voltage of the regulator 15 does not fall instantaneously when the accessory switch SW is turned off due to the time constant of the circuit, and the backup data is stored in the DAT as the backup memory during this fall.

When the vehicle is running, the CPU 7 calculates the running direction of the vehicle based on the output data of the direction sensor 1 at a predetermined cycle by a timer interrupt, and executes the running distance and the running distance by an interrupt for each fixed distance based on the output data of the distance sensor 3. Estimate the current location of the vehicle from the running direction, further estimate the current location of the vehicle based on longitude and latitude information obtained from GPS data by interrupting GPS reception, and estimate the current location by sensor data or
Map data of a certain area including the current position estimated by GPS data is collected from the CD-ROM, and this collected data is
It is temporarily stored in the AM 9 and supplied to the display device 16.
As a method for obtaining the traveling direction of the vehicle based on the output data of the direction sensor 1, a method described in JP-A-62-130013 or the like can be used.

The display device 16 includes a display 17 such as a CRT and a V (Vide
o) a graphic memory 18 such as a RAM, a graphic controller 19 for drawing map data sent from the system controller 5 as image data in the graphic memory 18 and outputting the image data, and an output from the graphic controller 19 And a display controller 20 that controls the display 17 to display a map based on the image data to be displayed. Input device 21
Is composed of a keyboard or the like, and issues various commands and the like to the system controller 5 by key input by the user.

Next, a processing procedure for determining the current position of the vehicle, which is executed by the CPU 7 based on the GPS data, will be described with reference to the flowchart of FIG. This subroutine reads the map data group of a certain range including the current position from the CD-ROM while recognizing the current position of the vehicle, displays the map data group on the display 17 as a map around the current position of the vehicle, and displays the map on the map. A main routine (not shown) for performing processing for displaying the own vehicle position indicating the current position of the vehicle, and the like.
Is called and executed by the GPS reception interrupt during the execution of.

In response to the GPS reception interrupt, the CPU 7 first obtains the current running direction of the vehicle (step S1). This running direction is, for example, from the direction of the speed vector obtained from GPS data,
Alternatively, it can be obtained by a known method based on the output data of the direction sensor 1 as described above. continue,
The CPU 7 obtains a difference (ΔX _G , ΔY _G ) between the current value and the previous value of the longitude and latitude information obtained from the GPS data (step S2),
The difference (ΔX _G , ΔY _G ) is added to the coordinate data of the current position determined last time, and the coordinate data obtained thereby is used as the coordinate data of the estimated current position (step S3).

Next, the CPU 7 searches for a road segment data group preferably representing a road segment closest to the estimated current position from a map data group of a certain range of areas centered on the current position (step S4). As a method of searching for the nearest road segment data group, a method described in Japanese Patent Application Laid-Open No. 63-115004 can be used. At this time, it is better to extract a plurality of road segment data groups as candidates. Subsequently, the CPU 7 determines that the distance from the estimated current position to the coordinates of the intersection of the perpendicular drawn down to the nearest road line segment and the road line segment, that is, the shortest distance from the estimated current position on the nearest road line segment is equal to or less than a predetermined value. It is determined whether or not the angle is equal to or smaller than a predetermined value (step S5), and it is determined whether or not the angle of the road line segment substantially matches the traveling azimuth obtained in step S1 (step S6). If the angle of the nearest road line segment does not match the traveling direction, the CPU 7 selects the next candidate road line segment data (step S7), and thereafter returns to step S5 to execute the same processing.

If the angle of the nearest road line segment substantially matches the current running direction, the CPU 7 corrects the coordinate data so that the estimated current position is located on the nearest road line segment (step S8), and the corrected coordinates The data is used as the coordinate data of the determined current position (step S9). After setting the coordinate data of the determined current position or when it is determined in step S5 that the distance from the estimated current position to the intersection coordinates on the nearest road segment exceeds a predetermined value, the CP
U7 holds the current value of the longitude / latitude information based on the GPS data as the previous value (step S10), and further holds the current value of the coordinate data of the determined current position as the previous value (step S1).
1).

Thus, a series of processes for determining the current location of the vehicle is completed, and thereafter, this process is repeated every time GPS is received.

Next, another procedure for determining the current position of the vehicle, which is executed by the CPU 7, will be described with reference to the flowchart of FIG. In the present embodiment, the current position is determined using both the sensor data of the direction sensor 1 and the distance sensor 3 and the GPS data. This subroutine is called and executed at predetermined intervals during the execution of the main routine.

First, the CPU 7 calculates the traveling amount (Δx, Δy) of the vehicle per unit time from the sensor data of the direction sensor 1 and the distance sensor 3.
Is calculated (step S21), and the traveling amounts per unit time (Δx, Δy) are integrated (step S22), and this process is repeated until it is determined in step S23 that GPS reception has been performed.
As a result, the amount of travel (ΔX _S , ΔY _S ) of the vehicle from the time of receiving the previous GPS to the time of receiving this GPS is obtained.

Once it determined that the GPS receiver, CPU 7 is the difference ([Delta] X _G between the present value and the previous value of the longitude and latitude information obtained from the GPS data by the same processing as steps S2, S3 in Figure 2,
ΔY _G ) is obtained (step S24), and the difference (ΔX _G , ΔY _G ) is obtained.
Is added to the coordinate data of the previously determined current position to obtain the coordinate data of the first estimated current position (step S2
5), and the travel amount (ΔX _S , ΔY _S ) obtained in step S22
Is added to the coordinate data of the previously determined current location to obtain the coordinate data of the second estimated current location (step
S26).

Subsequently, the CPU 7 obtains the absolute value of the difference between the coordinate data of the first and second estimated current positions (step S27), and determines whether or not the absolute value is equal to or larger than a predetermined value (step S2).
8). If the difference absolute value is equal to or greater than the predetermined value, then PDOP (P
It is determined whether or not the osition Dilution of Precision (position accuracy deterioration coefficient) value is equal to or less than a predetermined value (step S29). This P
The DOP value is a value indicating the state of the position of the satellite. The smaller the value sent from the GPS receiver, the better the positional relationship between the satellites and the higher the accuracy. If the PDOP value is equal to or less than the predetermined value, the coordinate data representing the absolute position based on the GPS data is selected as the coordinate data of the current estimated current position (step S30). (1) The coordinate data of the estimated current position is selected as the coordinate data of the current estimated current position (step S31).

If it is determined in step S28 that the absolute value of the difference is smaller than the predetermined value, the CPU 7 selects the coordinate data of the second estimated current position based on the sensor data as the coordinate data of the current estimated current position (step S32), and obtains the coordinate data in step S22. The travel distances (ΔX _S , ΔY _S ) are cleared (step S33), and the coordinate data of the estimated current position selected in step S30 or S32 is processed by the same processing as step S4 to step S11 in FIG. A process for correcting the data so as to be located one minute above and using the corrected coordinate data as the coordinate data of the determined current position is executed (step S34), and a series of processes is completed as described above.

In this way, when the absolute value of the difference between the first and second estimated current locations is equal to or greater than a predetermined value, the PDOP value is determined instead of simply setting the first estimated current location as the estimated current location.
That is, when the GPS absolute position is set as the estimated current position when the PDOP value is a good value, the estimated current position is reset at this time, so that the reliability of the subsequent current position estimation is improved.

As described above, in the vehicle-mounted navigation device according to the present invention, while recognizing the current location of the vehicle based on the GPS data, a map data group of a certain range including the current location is extracted from the storage medium, and the vehicle data is extracted. The current location and the map around the current location are displayed on the display unit, the difference between the current value and the previous value of the longitude and latitude information obtained from the GPS data is obtained, and this difference is added to the coordinate data of the last confirmed current location. Since the coordinate data obtained is used as the coordinate data of the estimated current position, the current position of the vehicle can be almost accurately estimated even when the accuracy of the GPS data is poor.

In particular, a search is made from a map data group for a road segment data group representing a road segment in the vicinity of the estimated current location, and a correction is made so that the estimated current location is located on the road segment represented by this road segment data group. By using this as the coordinate data of the determined current location, the longitude and latitude based on the GPS data are not regarded as absolute positions, and the road line segment represented by the map data is determined as the current location. Even if the accuracy of is not sufficient, the present location can be displayed on the map without a sense of incongruity.

In addition, the current position of the vehicle can be estimated almost accurately using only GPS navigation, and the estimated current position can be reliably corrected on the road on which the vehicle is actually traveling, so that the current position of the vehicle can be accurately displayed on a map.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an in-vehicle navigation device according to the present invention, FIG. 2 is a flowchart showing a processing procedure for determining a current position coordinate of a vehicle executed by a CPU, and FIG. 3 is executed by a CPU. It is a flowchart which shows the other processing procedure which determines the present location coordinate of a vehicle. Explanation of the reference numerals of the main parts 1 ... azimuth sensor, 3 ... distance sensor 4 ... GPS receiver 5 ... system controller 10 ... CD-ROM driver 17 ... display

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuhiro Akiyama 25-1, Nishimachi, Yamada-shi, Kawagoe-shi, Saitama Japan JP-A-61-196117 (JP, A) JP-A-63-6414 (JP, A)

Claims (4)

(57) [Claims] 1. A GPS receiver for measuring an absolute position of a vehicle and outputting coordinate data corresponding to the determined absolute position, and road data obtained by digitizing each point on a road segment of a map. Reading means for reading the map data group from a storage medium in which a plurality of map data groups respectively corresponding to a plurality of areas are stored; a certain range including the current position while confirming the current position of the vehicle based on the coordinate data. An in-vehicle navigation device configured to extract a map data group of a region from the storage medium and display a map around the current location of the vehicle and the current location on a display unit, the current value of longitude and latitude information obtained from the coordinate data. Means for obtaining a difference between the current value and the previous value; and means for obtaining coordinate data obtained by adding the difference to the coordinate data of the previously determined current position as coordinate data of the estimated current position; Means for searching, from the map data, a road segment data group representing a road segment in the vicinity of the current measurement location, and the estimated current location is located on the road segment represented by the searched road segment data group. Means for correcting the coordinate data so that the coordinate data becomes the coordinate data of the determined current location. 2. The method according to claim 1, wherein the angle of the road segment represented by the searched road segment data group substantially matches the direction of a velocity vector obtained from output data of the GPS receiver. Car navigation system. 3. An azimuth sensor for detecting a running azimuth of a vehicle, wherein an angle represented by the searched road segment data group substantially coincides with a running azimuth obtained from output data of the azimuth sensor. The vehicle-mounted navigation device according to claim 1. 4. A GPS receiver for measuring an absolute position of a vehicle and outputting coordinate data corresponding to the measured absolute position, a distance sensor for detecting a traveling distance of the vehicle, and a bearing for detecting a traveling direction of the vehicle. Reading means for reading the map data group from a storage medium including a sensor and a plurality of map data groups each including a plurality of map data groups corresponding to a plurality of areas, each of which includes road data obtained by digitizing each point on a road segment of the map; And, while recognizing the current position of the vehicle based on the output data of the GPS receiver or the output data of the distance sensor and the direction sensor, a map data group of a certain area including the current position is extracted from the recording medium. An on-vehicle navigation device configured to display a map around the current location of the vehicle and the current location on a display unit, wherein longitude and latitude information obtained from output data of the GPS receiver is provided. Means for calculating a difference between the current value and the previous value; means for adding coordinate data obtained by adding the difference to the coordinate data of the last confirmed current position to be coordinate data of the first estimated current position; and the distance sensor and the direction sensor Means for obtaining coordinate data of a second estimated current position based on the respective output data and the coordinate data of the last confirmed current position; and an absolute value of a difference between each of the coordinate data of the first and second estimated current positions being equal to or more than a predetermined value. When the position accuracy deterioration coefficient is equal to or less than a predetermined value, the absolute coordinate data based on the output data of the GPS receiver is used as the coordinate data of the current estimated current position. When the position accuracy deterioration coefficient exceeds the predetermined value, the coordinates of the first estimated current value are used. Means for making data the coordinate data of the current estimated current location; and means for searching the map data for a road segment data group representing road segments near the estimated current location. Means for correcting the coordinate data so that the estimated current position is located on the represented road line segment based on the searched road line data group, and using the corrected coordinate data as coordinate data of the determined current position. In-vehicle navigation device.