JPS63186400A - Navigation system for automobile - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a navigation system for a car, and more specifically, a car navigation system that detects the car's current position by receiving Loran C signal radio waves and displays it on a two-dimensional screen. regarding navigation systems.

2. Description of the Related Art Conventionally, a Loran C receiver is known which detects the current position by receiving radio waves from, for example, a 0570 station. Such a Loran C receiver is disclosed in, for example, Japanese Patent Laid-Open No. 60-53864.

Problems with the Prior Art When detecting the current position from the Loran C signal, position detection errors occur depending on the radio wave reception conditions.

Therefore, unless this error is corrected, the current position cannot be accurately obtained, but conventional devices have a problem in that such error correction is not sufficient.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a navigation system for a vehicle that can suitably correct detection errors caused by region.

Composition of the Invention The automobile navigation system of the present invention includes a local transmitting station that is installed at a predetermined point and transmits local radio waves to a small area with a radius of 200 m or less, and receives Loran C signal radio waves to detect the current position. A Loran C receiver, a local radio wave receiver, and when the local radio wave receiver receives local radio waves, the difference between the installation position of the local transmitting station and the current position output from the Loran C receiver is used as a correction value. A correction means that performs position correction in addition to the current position that is calculated and then output by the Loran receiver, and a position detection that displays the current position of the vehicle on a secondary screen based on the position signal output from the correction means. The present invention is characterized in that it is equipped with an in-vehicle navigation device having a display means.

FIG. 3 shows an example of the relationship between the position detected by the Loran C signal and the true position in the affected area. Uchi, true iMP
The devices composed of Loran C signals received at +, P2, and Px are Q1+02 and Q3, respectively, and both are offset by about 800 meters north and south.

This true place ii! P+ + P2 + P3 and detection position Q.

, Q2. The inventors of the present invention found that the deviations of Q, are approximately equal in a certain region.

Therefore, if this deviation is detected at a certain point, by using it as a correction value, the true position can be easily obtained from the detected position by the Loran C signal within a certain area.

Now, in the present invention, a local transmitting station is provided at a known location. If the car can receive the local radio waves, the car can be considered to be at a known location where the local transmitting station is installed, since the local radio waves are weak and reach only within a small area. In other words, the true location of the car is known. Therefore, by calculating the difference between the detected position based on the Loran C signal and its true position at this time, a correction value for this area can be obtained. Then, by correcting the detected position from the Loran C signal with this correction value, the true position can be easily obtained.

Practical Aspects Below, the present invention will be explained in more detail based on the embodiments shown in the drawings. Here, FIG. 1 is a schematic diagram of an automobile navigation system according to an embodiment of the present invention, FIG. 2 is a conceptual diagram explaining the principle of calculating correction values, and FIG. 3 is a map showing an example of the installation of local transmitting stations. Figure 4 is a waveform diagram showing the received waveform of the Loran C signal radio wave, Figure 5 is a graph showing the relationship between the noise level and the radius of the area figure, and Figure 6 is the position and size of the area figure on the two-dimensional screen. The schematic diagram, FIG. 7, is a conceptual diagram of a large number of stored maps. Note that the present invention is not limited to the embodiments shown in the figures.

As shown in FIG. 1, an automobile navigation system 11 is composed of a local transmitting station 1 and an on-vehicle navigation device 10. As shown in FIG.

The local transmitting station 1 is installed at a predetermined point and has a radius of 200
It transmits local radio waves to a small area of less than m. The predetermined points are provided, for example, every 1Qkm of the main road. The local radio waves include a signal that allows the location of the local transmitting station to be recognized.

As a specific example of the local transmitting station 1, as shown in Fig. 3, there is a local transmitting station that is installed at an intersection P of a major road and transmits weak local radio waves that reach a small area C' with a radius of approximately 150 m. Can be mentioned. The latitude of this point is B2. Longitude is expressed as +-.

On the other hand, an in-vehicle navigation device! ! 10 is a Loran C receiver 2, a local receiver 3, a correction circuit 4, a map selection circuit 5, a map memory 6, and an area figure generation circuit 7.
and an image display device 8.

The Loran C receiver 2 receives the Loran C signal radio wave, detects the latitude B & longitude of the current position, and outputs the detected latitude and longitude. Furthermore, the noise level R is calculated and output as an index indicating the reception state of radio waves. This noise level R is, for example, the ratio of the amplitude N of the bank ground noise to the amplitude P of the Loran C signal, as shown in FIG.

The local receiver 3 receives local radio waves from the local transmitting station 1, identifies the local transmitting station, and determines the latitude B of the point of the local transmitting station from pre-stored data.
, and longitude are extracted and outputted to the correction circuit 4.

The correction circuit 4 receives point data P from the local receiver 3.
When (BP, LP) is given, the difference from the detected position iQ (B, L) by the Loran C receiver 2 at that time is calculated.

That is, as shown in FIG. 2, the difference vector u(aI
, , aI).

Then, the vector size is set as a correction value.

The reason why vector theft is used as a correction value is as follows. That is, the fact that weak local radio waves could be received means that the car is at point P of the local transmitting station. However, if the detection position of the Loran C receiver 2 at this time is point Q, the difference between both points P and Q is the value to be corrected. Therefore, the vector 100 of the difference becomes the correction value.

Once the correction values are determined in this way, the correction circuit 4 adds a vector to the latitude B and longitude output from the Loran C receiver 2, and outputs the corrected latitude B' and longitude L'. do. Therefore, latitude B' and longitude L' represent the true position of the vehicle.

When the latitude B' and longitude L' are inputted from the correction circuit 4, the map selection circuit 5 selects the optimal map from among the many maps (for example, M1 to M5 in FIG. 7) stored in the map memory 6. Outputs a map signal to select and display that map.

On the other hand, the area figure generation circuit 7 generates and outputs a position (x, y) corresponding to the map displayed on the two-dimensional screen based on the latitude B' and longitude L' input from the correction circuit 4. do.

Also, based on the noise level R input from the Loran C receiver 2, it outputs a radius signal of an area figure.

The correspondence between the noise level R and the radius signal r is made based on the graph shown in FIG. 5, for example. For example, if the noise level R is 20% or less, the radius signal r has a value corresponding to an actual distance of 50 m. Further, when the noise level R becomes 70%, the radius signal r becomes a value corresponding to an actual distance of 250 m.

The image display device 8 displays the road map M on a two-dimensional screen based on the map signal input from the map selection circuit 5. Also, based on the area signal (x, y, r) inputted from the area figure generation circuit 7, as shown in FIG. 6, the position ii! on the two-dimensional screen! i: A circular area figure A with a radius r (however, the radius on the screen is the actual distance reduced by the scale of the map M) is displayed at (x, y).

Therefore, in the end, as shown in Figure 1,
An image in which area figure A and area figure A are superimposed is obtained.

In this way, regional errors are corrected from the detected position of the Loran C signal, so the true current position of the vehicle can be obtained.

Note that the radius of area figure A (therefore, the area) is expanded or contracted according to the magnitude of detection error due to the reception state of radio waves.
It becomes possible to read the current position of a car with an accuracy commensurate with the position detection accuracy.

Instead of or in addition to the noise level R, the reception strength of the radio waves, waveform distortion, etc. may be used as an index indicating the reception state of the radio waves.

Effects of the Invention According to the present invention, there is a local transmitting station that is installed at a predetermined point and transmits local radio waves to a small area with a radius of 200 meters or less, and a Loran C receiver that receives Loran C signal radio waves and detects the current position. machine, a local radio wave receiver,
When the local radio wave receiver receives the local radio wave, the location of the local transmitting station and the Loran C receiver (':
A correction means that calculates the difference between the current positions output by the five aircraft as a correction value, and then performs position correction by adding the correction value to the current position output by the Loran receiver, and 2 based on the position signal output by the correction means. There is provided a navigation system for a car, comprising an in-vehicle navigation device having a position detection display means for displaying the current position of the car on a screen, and thereby automatically correcting detection errors depending on the region. Since the corrected value is constantly updated to the optimum value by passing near the local transmitting station, the current position of the vehicle can always be accurately known.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an automobile navigation system according to an embodiment of the present invention, FIG. 2 is a conceptual diagram explaining the principle of calculating correction values, FIG. 3 is a map showing an example of installation between local transmissions, and FIG. The figure is a waveform diagram showing the received waveform of the Loran C signal radio wave, Figure 5 is a graph showing the relationship between the noise level and the radius of the area figure, and Figure 6 is a schematic diagram showing the position and size of the area figure on a two-dimensional screen. , FIG. 7 is a conceptual diagram of a large number of stored maps. (Explanation of symbols) l... Local transmitting station 2... Loran C receiver 3... Local receiver 4... Correction circuit 5...
・Map selection circuit 6...Map memory 7...
Area figure generation circuit 8...Image display screen lO...
In-vehicle navigation device 11...Automobile navigation system M...Map A...Area figure size...Correction vector P...Local transmitting station installation point Q...Detected position by Loran C signal. Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Takeshi Honsho Figure 5 Figure 3 LOl-”

Claims (1)

[Claims] 1. (a) A local transmitting station that is installed at a predetermined point and transmits local radio waves to a small area with a radius of 200 m or less, and (b) A local transmitting station that receives Loran C signal radio waves and determines the current location. A Loran C receiver to detect, a local radio wave receiver, and when the local radio wave receiver receives local radio waves, correct the difference between the installation position of the local transmitting station and the current position output from the Loran C receiver. a correction means for correcting the position by adding the corrected value to the current position output by the Loran receiver, and displaying the current position of the car on a secondary screen based on the position signal output from the correction means. 1. A navigation system for an automobile, comprising an on-vehicle navigation device having a position detection and display means.