JPH08334341A - Car navigation system - Google Patents

Abstract

(57) [Summary] [Purpose] Always display the correct current location. [Configuration] An average value and a variance of a difference between a current location detected by GPS navigation and a current location detected by self-contained navigation are calculated under predetermined detection conditions, and the average value is larger than a first threshold value and dispersed. Is smaller than the second threshold value, G
The current position is corrected to a point that internally divides the current position detected by PS navigation and the current position detected by self-contained navigation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle navigation system for displaying a current position on a road map to guide an occupant, and more particularly to an on-vehicle navigation device improved so as to always display an accurate current position.

[0002]

2. Description of the Related Art A GPS navigation device that receives GPS radio waves to detect the current position, and a self-contained navigation device that detects the current position based on the traveling distance and traveling direction detected by a sensor and road map data. Equipped with and GPS
When the difference between the current position detected by the navigation device and the current position detected by the self-contained navigation device exceeds a predetermined value, the vehicle-mounted navigation that corrects the current position of the self-contained navigation device with the current position detected by the GPS navigation device A device is known (see, for example, JP-A-1-316607).

However, since the detection accuracy of the current position detected by the GPS navigation device varies depending on various conditions on the transmitting side and the receiving side, the current position of the self-contained navigation device may be erroneously corrected in some cases. .

An object of the present invention is to provide a vehicle-mounted navigation device that always displays the accurate current position.

[0005]

In order to achieve the above object, the present invention provides a GP which detects the current position by GPS navigation.
The S navigation means and the self-contained navigation means for detecting the current position by the self-contained navigation are applied to the vehicle-mounted navigation device for displaying the current position on the road map to guide the occupants. Calculating means for calculating an average value and a variance of the difference between the detected current position and the current position detected by the self-contained navigation means; and the average value calculated by the calculating means is larger than a first threshold value, When the variance calculated by the calculating means is smaller than the second threshold value, the current position is divided into the current position detected by the GPS navigation means and the current position detected by the self-contained navigation means. And a current position correcting means for correcting the current position.

[0006]

The average value and variance of the difference between the current position detected by GPS navigation and the current position detected by self-contained navigation are calculated under predetermined detection conditions, and the average value is larger than the first threshold value and dispersed. Is less than the second threshold, GP
The current position is corrected to a point that internally divides the current position detected by S navigation and the current position detected by self-contained navigation.

[0007]

FIG. 1 is a functional block diagram showing the structure of an embodiment. The vehicle route guidance device of this embodiment is mainly composed of a microcomputer. The azimuth sensor 1 detects the traveling direction of the vehicle, and the detected traveling direction information is A / D.
CPU 4 via converter 2 and interface circuit 3
Send to. An optical fiber gyro or a vibration gyro can be used for the orientation sensor 1. Vehicle speed sensor 5
Generates a pulse signal for each predetermined traveling distance of the vehicle and outputs the pulse signal to the CPU 4 via the interface circuit 3. CP
U4 detects the traveling distance of the vehicle by counting the number of pulses of this pulse signal. The GPS receiver 6 is a receiver of a position detection system using satellites, and sends information such as the current position of the vehicle, the traveling direction, the speed of the vehicle, and the acceleration to the CPU 4 via the interface circuit 3. The key 7 is an operation member for setting a destination of the vehicle and the like, and is connected to the CPU 4 via the interface circuit 3.

The CD-ROM 8 is a storage device for storing road map data, and a CP via the interface circuit 9.
It is connected to U4 and sends road map data of a specified range to CPU4 in response to a road map read command from CPU4. The road map data is stored hierarchically according to the road type from the lower level to the upper level such as narrow streets, major local roads, prefectural roads, national roads, and highways. It should be noted that this road map data is composed of digitized data, and expresses a road by a node indicating an intersection or a bending point of the road, and a link on a straight line connecting the node, and the node and the link Information such as coordinates and road types is stored. The display 10 for displaying the road map is connected to the CPU 4 via the graphic controller 11, and displays the optimum route to the destination and the current position mark of the vehicle in a superimposed manner on the road map. In addition, the road map displayed on the display 10 is a bird's-eye view method display by the key 8,
It is possible to switch to a plan view display or a combination display. The V-RAM 12 stores road map data, and C
It outputs to the display 10 via the graphic controller 11 according to the display command from PU4. Further, the CPU 4 has a RAM 13 for temporarily storing various data.
A ROM 14 for storing a control program described later or the like is connected. The CPU 4 executes a processing program described later to correct the current location. In addition, the road map data of the two-dimensional plane is converted into the road map data of the bird's-eye view system, the road map of the bird's-eye view system or the road map of the plan view system is drawn on the display 10, and the character information and the current location of the vehicle are displayed on the map. And the optimum route to the destination are superimposed and drawn.

Now, the method of correcting the current position in this embodiment will be described. In the present invention, the current position of self-contained navigation is corrected with the accurate current position detected by GPS navigation. In addition, GP
In the S navigation, GPS signal radio waves are received by the GPS receiver 6 and positioning calculation is performed to obtain information such as the current position of the vehicle, the traveling direction, the speed of the vehicle, and the acceleration. Also,
The self-contained navigation is to calculate a traveling locus based on the traveling direction detected by the direction sensor 1 and the traveling distance measured by counting the pulse signals from the vehicle speed sensor 5, and based on the traveling locus and road map data. Map matching is performed to identify the current location. Further, in the present invention, the current position is corrected by a statistical method using a predetermined number n of GPS navigation detected under a predetermined condition and the current position by self-contained navigation. The detection conditions of the current position used for the correction are as follows, for example. (1) When the current location detected by the autonomous navigation is not on the road, that is, the current location is not specified on any road. When it is specified on any of the roads, the current position detected by the autonomous navigation is considered to be reliable and is not corrected. (2) When the speed detected by GPS navigation is within a range from a predetermined lower limit value to a predetermined upper limit value. When the speed detected by GPS navigation is low or high, GPS
The current location is not corrected because the accuracy of navigation detection will be reduced. (3) When the acceleration detected by GPS navigation is less than a predetermined value. When the acceleration detected by GPS navigation is high, the accuracy of detection by GPS navigation decreases, so the current position is not corrected. (4) When the current position detected by GPS navigation does not sometimes shake greatly and is moving stably along the road. (5) When a predetermined number of GPS signals are continuously received.
For example, the information detected immediately after leaving the tunnel is not adopted because it is unreliable. (6) When the current location detected by GPS navigation is in Japan. (7) Other.

Now, as shown in FIG. 2, the current position is detected in the order of G1, G2, ..., Gn-1, Gn by GPS navigation, and M1 by self-contained navigation almost in synchronization with the detection time by GPS navigation. , M2, ..., Mn-1, and Mn are detected in this order. The coordinates of the current position detected by GPS navigation are G1 (GX1, GY1), G2
(GX2, GY2), ..., Gn (GXn, GYn), and the coordinates of the current position detected by the autonomous navigation are M1 (M
X1, MY1), M2 (MX2, MY2), ..., Mn
Assuming that (MXn, MYn), the difference E between the current position of GPS navigation and the current position of self-contained navigation is

[Equation 1] Here, the average value Eav of the difference E is i = 1, 2, ...

[Equation 2] Furthermore, the variance V from the mean value Eav of the difference E is

(Equation 3) Becomes In this embodiment, when the average value Eav of the difference E and the variance V satisfy the following conditions, the current position of the self-contained navigation is corrected to the midpoint between the current position detected by the GPS navigation and the current position detected by the self-contained navigation.

## EQU00004 ## Eav> K1 and V <K2 where K1 and K2 are threshold values. In this embodiment, the corrected position of the current position is the midpoint between the current position of the GPS navigation and the current position of the self-contained navigation, but the corrected position is not limited to this embodiment and, for example, the GPS navigation is performed according to the difference Eav and the variance V. It may be a point that internally divides the present location of the vehicle and the current location of the autonomous navigation.

FIG. 3 is a flow chart showing a road map drawing program of one embodiment. The operation of the embodiment will be described with reference to this flowchart. When the main switch (not shown) of the key 7 is turned on, the CPU 4 starts executing the drawing program. In step 1, the destination information set by the key 7 is read, and in the following step 2, the current position and traveling direction of the vehicle are detected. The initial current position of the vehicle may be calculated by self-contained navigation or may be detected by GPS navigation. Also, both may be used in combination. In step 3, the optimum route from the current position to the destination is searched, and in the following step 4, the road map data around the current position is read from the CD-ROM 8. In step 5, a road map around the current position is drawn on the display 10, and the optimum route to the destination and the current position mark are drawn on the road map in a superimposed manner. In step 6, it is confirmed whether the vehicle has moved a predetermined distance or rotated a predetermined angle based on the detection results of the traveling distance and the traveling direction by the azimuth sensor 1 and the vehicle speed sensor 5, and if the vehicle moves or rotates. Go to step 7. In step 7, it is determined whether or not a predetermined number n of current positions have been detected by the GPS navigation and the self-contained navigation under the above-mentioned current position detection conditions, and if detected, the process proceeds to step 8, otherwise returns to step 4. The road map displayed on the display 10 is updated. When a predetermined number n of current locations are detected by the GPS navigation and the self-contained navigation under the above-mentioned current location detection conditions, the current location correction routine shown in FIG. 4 is executed in step 8 to correct the current location.

In step 11 of FIG. 4, the average value Eav of the difference E between the current position of the self-contained navigation and the current position of the GPS navigation is calculated by the formulas 1 and 2, and in the following step 12, the variance V of the difference E is calculated by the formula 3. To calculate. Next, in step 13, it is judged whether or not the average value Eav of the differences is larger than the threshold value K1 and the variance V is smaller than the threshold value K2. The current position of navigation is corrected to the midpoint between the current position detected by self-contained navigation and the current position detected by GPS navigation.

In the configuration of the above embodiment, the GPS receiver 6 constitutes GPS navigation means, the azimuth sensor 1, the vehicle speed sensor 5 and the CPU 4 constitute self-contained navigation means, and the CPU 4 constitutes arithmetic means and current position correction means.

[0014]

As described above, according to the present invention, the average value and the variance of the difference between the current position detected by GPS navigation and the current position detected by self-contained navigation are calculated under a predetermined detection condition, and the average is calculated. When the value is larger than the first threshold value and the variance is smaller than the second threshold value, the current position is divided into the current position detected by GPS navigation and the current position detected by self-contained navigation. Since the correction is made, the current position is corrected accurately, and the accurate current position is always displayed.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of an embodiment.

FIG. 2 is a diagram illustrating a method of correcting a current location according to an embodiment.

FIG. 3 is a flowchart showing a road map drawing program.

FIG. 4 is a flowchart showing a current position correction routine.

[Explanation of symbols]

 1 Direction Sensor 2 A / D Converter 3 Interface Circuit 4 CPU 5 Vehicle Speed Sensor 6 GPS Receiver 7 Key 8 CDROM 9 Interface Circuit 10 Display 11 Graphic Controller 12 V-RAM 13 RAM 14 ROM

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[Procedure amendment]

[Submission date] July 31, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

Claims (1)

[Claims] 1. A GP for detecting the present location by GPS navigation
In an in-vehicle navigation device that includes S navigation means and self-contained navigation means that detects the current location by self-contained navigation, and displays the current location on a road map to guide passengers, the GPS navigation means detects the current location under predetermined detection conditions. Calculating means for calculating an average value and a variance of the difference between the current position and the current position detected by the self-contained navigation means, and the average value calculated by the calculating means is larger than a first threshold value, and When the variance calculated by the calculation means is smaller than the second threshold value, the current location is corrected to a point that internally divides the current location detected by the GPS navigation means and the current location detected by the self-contained navigation means. An in-vehicle navigation device comprising a current position correcting means.