JPH09113295A - Navigation device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the probability that the actual present location of a vehicle is included in a present location mark even when the present location discriminated from GPS data contains a large error by calculating the error and, when the radius of error is larger than that of the present location mark, increasing the radium of the present location mark. SOLUTION: A navigation device for vehicle calculates the present location of its own vehicle by performing location measuring processing based on signals received from a GPS antenna 1. Then the device reads map data containing the calculated present location from a map data storing device 3 and displays 4 the map together with a present location mark indicating the present location. Then the device calculates the error contained in the calculated present location based on the signals received from the antenna 1. When the radius of the error is larger than that of the mark, the device increases the radius of the mark by a prescribed value. The device successively enlarges the mark by repeating the above-mentioned process until the radius of the mark reaches that of the error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle navigation device for receiving radio waves from an artificial satellite to calculate the present location and displaying the present location and a map.

[0002]

2. Description of the Related Art Conventionally, various proposals have been made that include a GPS system to calculate the present position of a vehicle and display a present position mark indicating the present position on a map.

[0003]

However, the GPS
An error is included in the current position calculated by the system, and if the error is large, there is a problem that the current position mark displayed on the map is largely deviated from the actual vehicle position. The present invention has been made in view of the above problems, and it is an object of the present invention to increase the probability that the actual vehicle position will be included in the current position mark even if the above error is large.

[0004]

In order to achieve the above object, in the invention described in claims 1 and 2, the error of the current position is calculated, and the size of the current position mark with respect to the map is calculated according to the calculated error. It is characterized by changing the. Therefore, even if the calculated error of the current position is large, by increasing the current position mark, it is possible to increase the probability that the actual vehicle position is included in the current position mark.

In the third aspect of the invention, the size of the current position mark is fixed to the upper limit value. Therefore, it is possible to prevent the current position mark from becoming abnormally large when the error is large.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall configuration of a vehicle navigation device. In FIG. 1, a GPS antenna 1
Receives radio waves from an artificial satellite (GPS satellite) and outputs a reception signal. The control device 2 performs the positioning process based on the received signal to calculate the current position of the vehicle. An amplifier circuit for amplifying a received signal from the GPS antenna 1 is provided in the control device 2.

Further, the control device 2 reads the map data from the map data storage device 3 having a storage medium such as a CD-ROM and causes the display device 4 to display a map including a current position mark indicating the current position of the vehicle and the current position. Control device 2
Is configured to include computer means such as a microcomputer. Hereinafter, the arithmetic processing performed by the control device 2 will be described based on the flowchart shown in FIG.

First, based on the signal received from the GPS antenna 1, positioning processing is performed to calculate the current position of the vehicle (step 101). The map data including the calculated current position is read from the map data storage device 3, and the current position mark indicating the current position and the map are displayed on the display device 4 (step 102). An example of this display is shown in FIG. Next, G
An error included in the current position calculated based on the received signal from the PS antenna 1 is calculated (step 103).

This error includes an error due to the GPS satellite position and an error in the GPS satellite confidence. The error due to the GPS satellite position is determined by the number and position of the satellites that can be received.
This is the error included in the data transmitted from the GPS satellites. Therefore, the above-mentioned two types of errors are calculated based on the received signal from the GPS antenna 1. Note that calculation of such an error has been conventionally performed in a navigation device of a certain type. For example, in the case of a navigation device having a map matching function, the matching process is performed in consideration of the error. There is. Therefore, the same processing as this is performed in step 103.

FIG. 3 shows the relationship between the above-mentioned error, the calculated current position, and the actual vehicle position. With respect to the calculated current position, the actual vehicle position exists within an error radius that is the sum of the error due to the GPS satellite position and the error due to the GPS satellite confidence. Therefore, it is determined whether the error radius, which is the sum of the above two types of errors, is larger than the radius of the current position mark (step 104). If the radius of the current position mark is larger, the size of the current position mark is determined. Figure 4 (a)
Leave the normal size as shown in.

However, when the error radius is larger,
The current position mark is displayed larger by a predetermined value (step 105). Then, steps 104 and 105 are repeated until the radius of the current position mark becomes the error radius, and the display of the current position mark is sequentially increased. Therefore,
As shown in FIG. 4B, the current position mark is displayed in a large size, and the actual vehicle position is present within the current position mark. It should be noted that the actual vehicle position in FIG. 4 is given for the sake of explanation and is not actually displayed on the display device 4.

When the size of the current position mark reaches the upper limit value, the size of the current position mark is fixed at that stage (step 106). Therefore, even if the error is large, it is possible to prevent the current position mark from becoming abnormally large. In addition, in the above-mentioned embodiment, although the present position mark is enlarged, the scale of the map may be increased so that the present position mark may be relatively increased. Further, the color of the current position mark may be changed while making the current position mark larger.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a vehicular navigation device showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a calculation process of a control device 2 in FIG.

FIG. 3 is a diagram showing a relationship between a GPS error and an actual vehicle position and the like.

FIG. 4 is a diagram showing a display example of a display device 4.

[Explanation of symbols]

1 ... GPS antenna, 2 ... Control device, 3 ... Map data storage device, 4 ... Display device.

Claims (3)

[Claims] 1. A GPS antenna (1) for receiving radio waves from an artificial satellite, which calculates a current position of a vehicle based on the received signal, and a current position mark which indicates the current position based on the calculated current position. A vehicle navigation device adapted to display a map on a display means (4), means (103) for calculating an error of the calculated current position.
And means for changing the size of the current position mark with respect to the map according to the calculated error (104 to 106)
And a vehicle navigation device. 2. The vehicle navigation device according to claim 1, wherein the means for changing the size of the current position mark has a size such that the current position mark has a radius of an error of the current position. 3. The vehicle according to claim 1, wherein the means for changing the size of the current position mark includes means (106) for fixing the size of the current position mark to an upper limit value. Navigation device.