JPH0613976B2 - Vehicle guidance device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle running guidance device, and more particularly, to changing the scale of a map on which the current position is displayed in accordance with the detection accuracy of the current position of the vehicle. The present invention relates to a vehicle travel guidance device.

<< Prior Art >> A vehicle traveling guidance device is a device that guides the vehicle to a destination without error by displaying a traveling map and a current position of the vehicle on a display means such as a CRT together with a road map of a region where the vehicle is traveling. For example, Japanese Patent Laid-Open No. 58-70125 discloses an example thereof.

This type of device has a current position detecting means for detecting the current position of the vehicle.
As disclosed in the publication, there is provided a means for detecting the traveling distance and azimuth of a vehicle from a certain reference point and grasping the current position of the vehicle as a relative position from the reference point.

However, this current position detecting means has a drawback that the measurement errors of the traveling distance and the azimuth are accumulated and the accuracy is lowered.

Therefore, there has been proposed a means for receiving a radio wave emitted from a satellite and obtaining the current position of the vehicle as an absolute position (latitude / longitude) on the earth.

<< Problems to be Solved by the Invention >> The current position detecting means using the satellites described above is a Global Positioning Satellite System currently under development.
This system is called GPS (hereinafter abbreviated as m)), and this system is capable of receiving the radio waves emitted from a plurality of artificial satellites and measuring the current position of the vehicle with a maximum accuracy of about 20 m. .

However, the measurement accuracy of the current position detecting means varies depending on the position of the satellite, the perturbation of the satellite, the state of the ionosphere, and the like.

On the other hand, maps for displaying the points detected by the current position detection means are prepared only in the same scale in the conventional vehicle travel guidance device.

Therefore, even if the current position could be measured with high accuracy, displaying this on the map of the same scale could not transmit sufficient information to the user.

In other words, if you can measure the current position with high accuracy, you can transmit more detailed information to the user by enlarging and displaying the map that displays it, but there is a problem that this cannot be dealt with. It was

The present invention has been made in view of such problems, the object is to correspond to the measurement accuracy of the current location detection means, to display by selecting the scale of the map to display it, It is an object of the present invention to provide a vehicle running guidance device capable of presenting information corresponding to accuracy.

<< Means for Solving the Problems >> In order to achieve the above-mentioned object, the present invention provides a vehicle travel guidance apparatus, a display means (a) for displaying information for vehicle travel guidance, and a plurality of different scales. (B) a memory scale that stores the map of FIG. 1, a current position detection means (d) having at least a positioning means (c) that receives radio waves from a satellite and detects the current position of the vehicle, and the positioning means (c). ) Of the deterioration coefficient detecting means (e) for detecting the distance measurement error and one of the maps of the storage means (b) corresponding to the size of the deterioration coefficient detected by the deterioration coefficient detecting means (e). And a control means (g) for displaying the map specified by the selection means (f) on the display means (a).

Here, the deterioration coefficient (Geometrical Dilution of prec
ision, which is abbreviated as GDOP) is a coefficient that represents an increase in measurement error that is determined by a geometrical function between the satellite used and the vehicle when measuring the current position.

<< Operation >> According to the vehicle running guidance device having the above-described configuration, since the current position is displayed on the map of a scale corresponding to the magnitude of the measurement accuracy of the current location detection means, for example, when the accuracy is good, the image is greatly enlarged. The current position can be shown on the map and the information can be transmitted to the user according to the accuracy.

<Example> Hereinafter, a preferred example of the present invention will be described in detail with reference to the accompanying drawings.

2 to 4 show an embodiment of a vehicle travel guide device according to the present invention.

The vehicle travel guidance device shown in FIG. 2 has a display unit 10 for displaying information for guiding the travel of the vehicle (such as the current position of the vehicle and a destination) as shown in FIG. Storage means 12 for storing a plurality of different maps,
Current location detection means 1 having at least positioning means (GPS) for receiving radio waves from satellites and detecting the current location of the vehicle
4 and a control means 16 for selecting one from a plurality of maps of different scales in the storage means 12 corresponding to the size of the deterioration coefficient (GDOP) of the GPS and displaying it on the display means 10. It is composed of

The display means 10 is, for example, a monochrome or color CP.
T, liquid crystal display element, plasma display, electroluminescence, etc. are used, and the display information is controlled by the control means 16.

As the storage means 12, for example, a CD-ROM or a magnetic tape is used. Particularly, the CD-ROM has a large storage capacity, is compact, and has a short access time. Therefore, it is suitable as a storage means for mounting on a vehicle. In addition, information such as the start-up inspection procedure and the tire replacement procedure may be stored. To retrieve information from the storage means 12,
This is performed by mounting a storage medium such as a compact disk or tape on the reproducing device and controlling the reproducing device by the control means 16.

The current position detecting means 14 has the GPS as described above, but a known geomagnetic sensor may be installed together with the GPS.

The principle of detecting the current position by GPS will be described below.

As schematically shown in FIG. 3, the GPS is composed of a plurality of antennas A _{1 to} A ₄ distributed over the earth E at appropriate intervals, a plurality of satellites S _{1 to} S _4, and a user P. Each satellite S _{1 to} S ₄ is configured and controlled by the control station C via the antennas A _{1 to} A ₄ .

Further, each satellite S _{1 to} S ₄ has a receiver that receives signals from the antennas A _{1 to} A ₄ , and a transmitter that emits various information signals to the user P, and the user P is the satellite S ₁ . ~ S ₄ for receiving the signals from each.

Here, if there is a clock that is completely synchronized with the transmission point and reception point of the radio wave and the transmission signal is controlled by that clock, if the reception timing is measured at the reception point, the propagation of the radio wave between the transmission and reception points The time can be obtained, and the distance between the transmitting and receiving points can be obtained by multiplying it by the speed of light.
Now, there are three satellites S ₁ , S ₂ , S _{3 in} the field of view (receivable area) of the user P, and the respective satellites S ₁ , S ₂ , S ₃ transmit distance measurement signals by means of clocks that are synchronized with each other. And
Moreover, it is assumed that the positions of the satellites S _{1 to} S _{3 at} the time of reception have been accurately obtained. If the receiving time of these signals is measured at the receiving point, the distance between each satellite S ₁ , S ₂ , S ₃ and the receiving point can be obtained,
The position of the user P can be obtained as an intersection of three spherical surfaces centered on the respective satellites S ₁ , S ₂ and S ₃ .

However, in reality, it is difficult to completely synchronize the clocks of the transmitting point and the receiving point, and an error occurs due to the delay of the received signal. Moreover, in this system, as described above, the satellite S
_{Since the} measurement accuracy varies including the position error of _{1 to} S _{4 and} the measurement error due to the state of the ionosphere, the signals emitted from the satellites S _{1 to} S ₄ to the user P have a coefficient indicating the magnitude of the measurement error. The data of the deterioration coefficient (GDOP) is also included.

Table 1 below shows an example of the types and magnitudes of measurement errors that have been published, and by multiplying these values by GDOP, the accuracy when a user actually uses this system is shown. You can check it.

On the other hand, the control means 16 is composed of a so-called microcomputer in this embodiment, and has an input / output interface 16a connected to the display means 10, the storage means 12 and the present location detection means 14, respectively, and a read only memory (ROM). ) According to the procedure stored in 16b, the signal from the current position detecting means 14 is received and operated through the input / output interface 16a, the storing means 12 is controlled based on the result, and the stored information is displayed on the displaying means 10.
And a random access memory (ROM) 16d for temporarily storing the fetched data.

Particularly in the present invention, the control means 16 is the GPS described above.
It is configured to select and display one of a plurality of maps of different scales stored in the storage unit 12 corresponding to the size of the GDOP.

Explaining an example of the method of determining the scale of the map, first, the scale of the displayed map is determined by the following calculation formula.

Here, D is a size indicating the current position displayed on the display means 10, and usually has a diameter of about 4 mm.

Further, the GDOP value by GPS is divided into 10 steps in this embodiment as shown in Table 2 below, and the measurement accuracy at each step is estimated and set stepwise from the maximum accuracy of 20 m to the minimum accuracy of 200 m. Has been done. 20 × 1 in the above formula
0 ³ is this highest precision value.

Further, since the scale map is prepared at a scale of an integral multiple of 1/250000 (1 / 1.255, 1 / 50,000, 1 / 100,000 ...) And written in the storage means 12, The minimum scale map is selected from the scales larger than S ₀ calculated by the above equation.

That is, for example, if the GDOP value is 9 and D is 4 mm, Therefore, in this case, a scale map of 1 / 50,000 is selected, a map with a large scale is selected when the accuracy is good, and a map with a small scale is selected when the accuracy is poor.

FIG. 4 shows the details of the procedure for selecting the scale map by the control means 16. In this example, 1 / 12,500 to 1 / 10,000.
Up to 200,000 maps with different scales are prepared.
First, when the map scale determination routine is started in step, GPS reception of the current position detection means 12 is performed in step, and the current position is detected by the above-mentioned principle, and the GDOP value is also detected in step.

When the GDOP value is detected, S ₀ is calculated by the above equation in step, and the calculated S ₀ and the minimum scale value 12500 are compared in step. If this is smaller than 12500, 1/125 in step A map of various scales is displayed on the display means 10, and the process returns to the main routine in step.

On the other hand, if S ₀ is judged to be larger than 1125,000 at the step, comparison with the next scale value of 25,000 is made at the step, and when S ₀ is smaller than that value, the scale map of 1 / 25,000 at the step. Is displayed on the display means 10, the step is executed.

If it is determined in step that S ₀ is greater than 25000,
After that, comparison with smaller scale values (step,
) Is performed, and S _{0 is} smaller than the scale value at each step.
If is smaller, the process returns to the step after the step of displaying the corresponding scale map.

<< Effects of the Invention >> As described above in detail in the embodiments, in the vehicle travel guidance device according to the present invention, the current position detection means (GP) is used.
According to the current position detection accuracy of S), the scale of the map to be displayed is selected and displayed. Therefore, it is possible to provide the user with information near the current location corresponding to the accuracy and the user The reception status of GPS can be confirmed at the same time.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the device of the present invention, FIG. 2 is an overall block diagram showing an embodiment of the device of the present invention, FIG. 3 is an explanatory diagram showing the principle of GPS, and FIG. It is a flowchart figure which shows a procedure. 10 ... Display means, 12 ... Storage means 14 ... Present location detection means, 16 ... Control means

Claims (1)

[Claims] 1. A display means for displaying information for guiding a vehicle to travel, a storage means for storing a plurality of maps having different scales, and a radio wave from a satellite to detect the current position of the vehicle. A current location detecting means having at least a positioning means,
Deterioration coefficient detecting means for detecting a distance measurement error of the positioning means,
Selection means for selecting one from the maps of the storage means corresponding to the magnitude of the deterioration coefficient detected by the deterioration coefficient detection means; and control means for displaying the map specified by the selection means on the display means. A traveling guidance device for a vehicle, comprising: