JPH07260502A - Present position computing device - Google Patents

Abstract

PURPOSE:To provide a present position computing device with which an accurate vehicle position can be found by correcting a distance constant per rotation of a tire. CONSTITUTION:The device is provided with an optical fiber gyroscope 202 for detecting an advancing azimuth change, a vehicle speed sensor 203 for detecting vehicle speed by outputting pulses in proportion to output shaft rotation of a vehicle transmission, a GPS receiving device 205 for outputting a position, azimuth, speed and DOP value of the vehicle, and a controller 210 equipped with a CPU and memory, and compares speed obtained in a state of high reliability of the data because of a GPS signal and speed obtained through measurement in a state of stabilized tire rotation so as to correct a distance constant per rotation of a tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current position calculating device which is mounted on a moving body such as a vehicle and calculates the current position of the vehicle.

[0002]

2. Description of the Related Art The current position of a vehicle is generally calculated by determining the traveling direction of the vehicle with a direction sensor such as a gyro and by determining the traveling distance of the vehicle with a vehicle speed sensor or a distance sensor.

To determine the traveling distance of the vehicle, the rotational speed of the output shaft of the transmission or the tire is measured, and the rotational speed is multiplied by the distance constant per one rotation of the tire to determine the traveling distance of the vehicle. A means of calculating is used.

Further, in order to correct the error in such a means, so-called map matching, which is to correct the present position of the obtained vehicle by using the road data, is also performed, and the position calculation is performed. It is configured to increase accuracy.

However, even with such a configuration, when the vehicle travels on a road with few large curves such as an expressway, there is no singular point such as an intersection used for map matching, and therefore the vehicle position on the road data cannot be specified. , It becomes impossible to correct the vehicle position.

Further, during running, the tire diameter, that is, the distance constant, changes from time to time due to tire wear, expansion due to temperature changes, and the like. Therefore, an error occurs in the calculation of the traveling distance, and the current position cannot be calculated with high accuracy. For example, if there is an error of 1% in the traveling distance constant per one rotation of the tire, an error of 1 km will occur when the vehicle travels 100 km.

Of course, when traveling on an ordinary road, such an error can be prevented from being accumulated by map matching. However, since there is no curve or intersection when traveling on a highway, the error is not corrected. In addition, 1K
If an error of about m occurs, the difference from the true vehicle position is too large, and the correct position cannot be corrected even by the map matching process.

In order to solve such a problem, conventionally,
The distance constant per tire revolution is corrected by comparing the road data from when the vehicle turns the intersection (start point) to when it turns the next intersection (end point) with the traveling distance obtained from the measured number of revolutions. Was there. There is also an example in which the distance constant is corrected by comparing the distance on the map between the two beacons and the distance measured by traveling.

Although not a navigation device, a GPS device is used as in the example described in Japanese Patent Laid-Open No. 2-107959.
There is also a range finder and a speedometer that obtain a vehicle speed by using a signal and compare the detected vehicle speed with the detected rotation speed of the tire to make a correction.

[0010]

However, in the first prior art example described above, if the road is slightly curved or the vehicle meanders, a distance error will occur. Further, there is a problem that it is difficult to accurately specify the start and end points at the intersection. Similarly to the first conventional example, the second conventional example has a problem that an error occurs unless the road is a straight line and that a beacon facility that can be used by the vehicle is required.

Further, in the third conventional example, the traveling state of the vehicle at the time of correcting the distance meter and the speedometer are not taken into consideration at all. Originally, the tire distance constant depends on the weight and running speed of the vehicle, and the wear and temperature of the tire.
It changes from moment to moment. Furthermore, when the speed of the vehicle is low, the reliability of the speed information output from the GPS receiving device is lowered, and when the change of the speed of the vehicle is large, it takes time to calculate in the GPS receiving device. Delays will also have an effect. Therefore, even if the GPS signal is used, if the correction is performed in a state irrelevant to the traveling state of the vehicle, there is a problem that an accurate distance constant may not be obtained.

In order to solve the above problems, an object of the present invention is to calculate the current position by which the vehicle position can be obtained with high accuracy by correcting the speed detecting means in accordance with the running state of the vehicle. To provide a device.

[0013]

An object of the present invention is to provide an azimuth detecting means for detecting a traveling azimuth of a vehicle in a current position calculating device which is mounted on a vehicle and calculates the current position of the vehicle.
A first speed detecting means that is attached to a part of a driving unit that moves the vehicle and that detects a vehicle speed; a traveling distance calculating means that integrates the detected vehicle speeds to calculate a traveling distance of the vehicle; Based on the outputs from the detecting means and the traveling distance calculating means, the current position calculating means for calculating and outputting the current position of the vehicle and the radio signal from the outside are received, and the vehicle speed is calculated based on the received signal. The correction timing of the first speed detecting means is controlled according to the vehicle speed output from at least one of the second speed detecting means for detecting and the first and second speed detecting means, and the correction is performed. It can be achieved by a current position calculation device characterized by having a speed correction means for executing.

The above object is also to provide a speed correction device for correcting the speed detection means mounted on the vehicle, wherein the vehicle is mounted on a part of a drive unit for moving the vehicle to detect the vehicle speed. And a second speed detecting means for receiving a radio wave signal from the outside and detecting the vehicle speed based on the received signal, the first speed detecting means and the second speed detecting means being mounted. This can be achieved by a speed correction device characterized by controlling the correction timing of the first speed detecting means and executing the correction in accordance with the vehicle speed output from at least one of the means.

The above-described object is also to provide a azimuth detecting means for detecting a traveling azimuth of a vehicle and a part of a drive unit for moving the vehicle in a navigation device mounted on the vehicle to calculate and display a current position of the vehicle. The first speed detecting means is attached and detects the vehicle speed, the traveling distance calculating means for calculating the traveling distance of the vehicle by integrating the detected vehicle speeds, the azimuth detecting means and the traveling distance calculating means. A current position calculation means for calculating and outputting the current position of the vehicle based on the output, a display means for displaying the calculated current position of the vehicle on a map showing the surrounding area, and a map displayed by the display means. Storage means for storing data relating to the above, a second speed detecting means for receiving a radio wave signal from the outside, and detecting a vehicle speed based on the received signal, and a first speed detecting means and a second speed detecting means. And a speed correction means for controlling the correction timing of the first speed detection means according to the vehicle speed output from at least one of them, and a speed correction means for performing the correction. .

[0016]

In the present position calculating apparatus according to the present invention, the first speed detecting means is attached to a part of the drive unit for moving the vehicle and detects the vehicle speed, and the second speed detecting means. Receives a radio signal from the outside and detects the vehicle speed based on the received signal.

The speed correction means receives the vehicle speeds from these speed detection means, controls the correction timing of the first speed detection means according to the vehicle speed from at least one, and executes the correction.

Specifically, the correction is executed only when the vehicle is in a running state where the speed obtained by receiving the GPS signal can be regarded as a sufficiently reliable value. is there. When the correction is executed at such timing, the vehicle speed can be corrected with high accuracy, and as a result, the traveling distance and the current position can be determined with high accuracy.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present position calculating device to which the present invention is applied will be described.

The hardware of this embodiment is, for example, as shown in FIG.
It has a configuration as shown in. That is, in the present embodiment, the optical fiber gyro 202 that detects a change in the heading by detecting the yaw rate of the vehicle, and the vehicle speed that detects the vehicle speed by outputting a pulse in proportion to the rotation of the output shaft of the transmission of the vehicle. A sensor 203, an antenna 204 for receiving GPS signals from GPS satellites, and an antenna 20.
The GPS signal received in 4 is processed and the position, direction of the vehicle,
It has a GPS receiver 205 that outputs a speed, a VDOP value, and an HDOP value. Here, the VDOP value and the HDOP value are indexes of position accuracy determined by the arrangement state of satellites.

In the present embodiment, further, a switch 206 for accepting a scale change command for a displayed map from a user (driver), a CD-ROM 207 for storing digital map data, and the CD-ROM 207 are read. A driver 208 for taking out, a display 209 displaying a map around the current position, a mark indicating the current position, etc.
Have and.

This embodiment further includes a controller 210 for controlling the operation of each peripheral device described above.

The controller 210 counts the number of pulses output from the A / D converter 211 for converting the signal (analog signal) of the optical fiber gyro 202 into a digital signal and the vehicle speed sensor 203 every 0.1 seconds. A counter 217, a serial interface 218 that receives data from the GPS receiver 205, and a switch 206.
Parallel I / O 212 that recognizes the pressure of CD and RO
DMA to transfer the map data read from M207
(Direct Memory Access) controller 213 and display processor 21 for displaying a map image on display 209
4 and.

The controller 210 further includes a microprocessor 215 and a memory 216. The microprocessor 215 receives signals from the peripheral sensors and devices obtained through the above-mentioned units, performs processing based on those signals, calculates the current position of the vehicle, and displays the current position via the display processor 214. Day Play 209
To display. This display of the vehicle position is superimposed on the already displayed map, and the user can know the current position of the vehicle on the map.

The memory 216 includes a ROM that stores the contents of the processing described below and a microprocessor 21.
5 has a RAM used when processing is performed.

Next, among the operations of this embodiment, the operations required for calculating the current position of the vehicle will be described with reference to FIGS. 3, 4 and 5. Here, FIG. 3, FIG. 4, and FIG. 5 respectively show a process of calculating the traveling direction and traveling distance of the vehicle, a process of determining the current position of the vehicle from the calculated traveling direction and distance, and the obtained vehicle. It is a flow chart which shows the processing which displays a position and a direction.

First, the processing flow for obtaining the traveling direction and traveling distance of the vehicle will be described with reference to FIG. This process is a routine started every 100 mS.

In this routine, first, the A / D converter 2
The output value of the gyro 202 is read from 11 (step 401). Since the azimuth change is output to the output value of the gyro 202, only the relative value of the traveling azimuth of the vehicle can be detected. Therefore, next, the absolute position, the absolute azimuth, the absolute speed, and the DO of the vehicle calculated and output by the GPS reception device 205 from the serial interface 218 are output.
The P value is read (step 402), and the absolute azimuth (GPS azimuth) calculated from this GPS signal and the gyro 2
The estimated heading of the vehicle is determined using the heading change (gyro output) output from 02 (step 403).

As a method of determining the estimated bearing, for example, when the GPS signal can be received, the GPS bearing is output as it is, and when the GPS signal cannot be received, the GPS bearing obtained by the previous routine processing is obtained. And a gyro output are added to obtain the azimuth. Also,
When the vehicle speed is low, the GPS azimuth has a large error. Therefore, the GPS azimuth may be used only when the vehicle speed is equal to or higher than a certain level.

Next, the number of pulses output from the vehicle speed sensor 203 is counted by the counter 217 every 0.1 second, and the count value is read (step 404). The read distance is multiplied by a preset traveling distance constant per one rotation of the tire to obtain the traveling distance in 0.1 second (step 405).

Next, the traveling distance value per 0.1 second thus obtained is integrated with the previously obtained value,
It is checked whether the traveling distance of the vehicle has reached 10 m (step 406) and if it is less than 10 m (step 406).
No), the process of this time is ended and a new process is started.

As a result of the traveling distance calculation processing, when the accumulated traveling distance becomes 10 m (Yes in step 406).
s), the traveling direction and the traveling distance (10 m) at that time are output (step 407). In step 407, the cumulative distance is reset and a new cumulative distance is started.

Next, the processing for obtaining the current position of the vehicle based on the traveling direction and traveling distance output in the processing of FIG. 3 will be described with reference to the flowchart of FIG. This process is started in response to the output of the traveling direction and traveling distance from FIG. 3, that is, the process is started every time the vehicle advances by 10 m.

First, the traveling direction and traveling distance output in step 407 of FIG. 3 are read (step 501).
Next, based on these values, the amount of movement of the vehicle is obtained separately in the latitude and longitude directions. Further, the movement amount in each of these directions is added to the current position of the vehicle obtained in the previous processing to obtain the current position (A) (step 50).
2).

If there is no position obtained last time, such as immediately after the start of the apparatus of this embodiment, after receiving the GPS signal,
Using the GPS position output by the GPS receiver 205,
Start these processes.

Next, a map around the current position (A) is displayed as C
The current position (A) is read from the D-ROM 207 via the driver 208 and the DMA controller 213.
The road data (line segment) within the preset distance D centering on is extracted (step 503). The distance D is
It may be a fixed value, but it was obtained from the previous process,
It may be a value determined based on the error cost value described below.

Here, the reason for determining the search range based on the error cost is as follows. That is, when the error cost is large, it is considered that the reliability of the position accuracy is low. For this reason, it makes more sense to search for a wider range and search for roads.

The road data is, for example, approximated by a plurality of line segments 81 to 85 connecting two points as shown in FIG. 8, and the data to be stored are the start point and end point of these line segments. It is possible to use a method of storing the coordinates of. For example, for the line segment 83, (x ₃ , y ₃ ) is stored as its start point and (x ₄ ,
y ₄ ) is memorized and used.

Next, from the line segments extracted in step 503, only the line segment whose azimuth is within a predetermined advancing direction and a predetermined traveling direction are extracted (step 5).
04). Further, with respect to all the extracted line segments, a perpendicular is drawn from the current position (A) and the length of the perpendicular is obtained (step 505).

Next, using the lengths of the perpendiculars, the error cost values defined below are calculated for all the line segments extracted in step 504.

Error cost = α × | advancing direction−line segment direction | + β × | length of perpendicular | (1) Here, α and β are weighting factors. These coefficients can be changed depending on the specific processing method used. For example, when importance is attached to a road having a close direction, α may be increased.

Next, of the line segments for which the error cost has been calculated, the line segment with the smallest error cost value is selected (step 506), and the point at which the selected line segment and the perpendicular line intersect (the perpendicular line segment). Nose) is set as the corrected current position (B) (step 507).

Next, the processing for displaying the current position (B) obtained by the processing of FIG. 4 on the map displayed on the display 209 will be described with reference to FIG. This process is 1
It is activated every second.

First, the parallel I / O 212 is used to check whether the switch 206 is pressed to instruct to change the map scale.
The content is judged by judging (step 601). If it is pressed (Yes in step 601), the predetermined scale flag is switched correspondingly (step 60).
2). Although there are other functions of the switch 206, they are not described because they are irrelevant to the operation of this embodiment.

Next, the current position (B) obtained by the processing of FIG. 4 is read (step 603) and step 602.
A map having a scale corresponding to the content of the scale flag switched by is displayed on the display 209, for example, in the state as shown in FIG. 2 (step 604).

The current position (B) of the vehicle and the traveling direction of the vehicle are displayed using, for example, the arrow symbol "↑" shown in FIG. 2 (step 605). Finally, the north mark indicating north and the distance mark corresponding to the scale are superimposed and displayed in an overlapping manner as shown in FIG. 2 (step 60).
6).

In the present embodiment, the vehicle position and direction are indicated by using the arrow symbols as described above. However, the display form of the vehicle position and direction in the present invention clearly shows the position and the traveling direction in the display state. The form does not matter as long as it is shown. Also, the map display form such as the north mark,
The display form is not limited as long as it clearly shows the peripheral state.

Next, the correction processing of the distance constant per one rotation of the tire, which is a feature of the present invention, will be described with reference to FIG. This distance constant is calculated in step 405 of the processing of FIG.
It is used to calculate the distance.

In this process, the vehicle speed obtained from the vehicle speed sensor 203 and the vehicle speed obtained from the GPS receiving device 205 are
The distance constant is corrected by making a comparison only while the conditions necessary for the predetermined correction are met. The condition here is, for example, that the vehicle speed value based on the GPS signal is highly reliable, that the tire condition is stable, or
That is, the output value of the vehicle speed sensor 203 is stable.

The process described below shows an example of a process flow in which such a condition is specifically set.

This process is started every one second, and as shown in FIG. 6, it is first determined from the output of the GPS receiving device 205 whether or not a GPS signal is received (step 101). If not received (No in step 101), this process ends. If it is received (Yes in step 101), it is determined whether the vehicle speed obtained from the vehicle speed sensor 203 is higher than 80 km / h (step 102). In this embodiment, the vehicle speed is defined by the following formula.

Vehicle speed = P × 36 × K (Km / h) (2) where P is the vehicle speed sensor 2 counted by the counter 217.
No. 03 is the number of pulses per 0.1 second, and K is a distance constant per one rotation of the tire.

If the calculated vehicle speed is low (No in step 102), this process is terminated. This is because when the vehicle speed is low, the moving distance per unit time is short and the accuracy of speed information obtained by the GPS signal to be referred to at this time is reduced.

If the vehicle speed is higher than 80 km / h (Yes in step 102), whether or not the vehicle speed obtained from the vehicle speed sensor 203 is stable in the past 5 seconds, that is, the difference between the maximum speed and the minimum speed for 5 seconds. Is determined to be within a predetermined value (step 103).

When the vehicle speed is fluctuating (step 103)
No), the process ends. This is because when the vehicle speed changes, the output of the vehicle speed sensor 203 is not stable, which may cause an error.
This is because an error may occur due to a time delay in reception of the S signal, a delay due to calculation of the GPS speed, or the like.

If the vehicle speed is stable (Yes in step 103), it is next determined whether HDOP is equal to or higher than a predetermined value (step 104). Here, HDOP is DO
It is one of the parameters in P, and is a parameter regarding the satellite constellation in the horizontal direction. If HDOP is greater than or equal to the predetermined value (Yes in step 104), this process ends.

If it is less than the predetermined value (N in step 104)
o), the ratio between the vehicle speed obtained by the vehicle speed sensor 203 and the vehicle speed obtained by the GPS receiving device 205 is calculated, and it is determined whether the value is within a predetermined value range (step 10).
5).

The process in step 105 is provided in order to avoid the vehicle speed obtained from the GPS signal, which may have a large error although it is extremely rare. Further, in this step, the vehicle speed sensor 203
Since the case where the value of is not stable is excluded, the distance constant is corrected only when the vehicle speed by the GPS signal and the vehicle speed by the vehicle speed sensor 203 are both stable.

Here, the ratio of the vehicle speed by the vehicle speed sensor 203 and the vehicle speed by the GPS signal (vehicle speed sensor vehicle speed / G
Although the PS vehicle speed) is used, the same effect can be obtained by means of taking the difference between these vehicle speed values.

If such a ratio is outside the predetermined range (No at step 105), this process is terminated, and if it is within the predetermined range (Yes at step 105), the value of the ratio is the last 10 times. Take a moving average of the data (Step 1
06).

In this embodiment, the distance constant per one rotation of the tire is corrected based on this average value. Specifically, considering the velocity obtained from the GPS signal as a true value, the distance constant per one rotation of the tire is divided by the previously obtained ratio, and the value obtained as the corrected distance constant (Step 107).

In step 107, the effect of thermal expansion of the tire may be corrected. That is, when the vehicle speed is about 100 km / h or more, the tire thermally expands and the distance per one rotation of the tire changes.
In order to correct this effect, the vehicle speed is divided into several stages as shown in FIG. 7, the expansion coefficient for each speed section is obtained in advance, and this is used to correct the already corrected distance constant. Can also be considered. In this case, the GPS vehicle speed is defined as follows.

GPS vehicle speed = P × 36 × K × tire expansion rate (Km / h) (3) where P is the vehicle speed sensor 2 counted by the counter 217.
No. 03 is the number of pulses per 0.1 second, and K is a distance constant per one rotation of the tire. Since the expansion rate differs depending on the speed, it is preferable to store the expansion rates for certain specific speed sections in a table format as shown in FIG.

In such a configuration, when the GPS vehicle speed is obtained from the GPS signal, the expansion coefficient can be specified based on the GPS vehicle speed, and the distance constant K can be obtained by finding the pulse number P. Based on these, the distance constant K is obtained from the above equation (3), and this is used as the corrected distance constant.

In the following, the traveling distance is calculated using the distance constant corrected as described above.

Next, the present position (present position (B)) obtained so far is corrected based on the obtained distance constant. That is, when the vehicle travels on a straight line after the position correction by the map matching performed at the time of turning the previous intersection, the error in the front-back direction may be accumulated.

In order to correct this error, the distance of the straight line portion that has traveled up to the present is obtained after the azimuth change has exceeded a predetermined value by turning at an intersection or the like last time (step 108), and is obtained first. The distance of the straight line portion is corrected by shifting the current position of the vehicle in the front-rear direction along the road by an amount corresponding to the ratio of the corrected distance constant to the distance constant before correction (step 109). .

According to the present embodiment, by comparing the highly reliable speed information obtained from the GPS signal with the speed information in a stable state obtained by measuring the rotation of the tire, Since the distance constant per one rotation is corrected, the correction accuracy is improved, and it is possible to provide the current position calculation device that can determine the current position of the vehicle with higher accuracy.

[0069]

According to the present invention, since the speed detecting means is corrected in accordance with the running condition of the vehicle, it is possible to provide a current position calculating device capable of obtaining the current position of the vehicle with higher accuracy. You can

[0070]

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a current position calculation device according to the present invention.

FIG. 2 is an explanatory diagram showing an example of a display form of the current position in the present invention.

FIG. 3 is a flowchart showing an example of processing for calculating a traveling direction and a distance according to the present invention.

FIG. 4 is a flowchart showing an example of current position calculation processing according to the present invention.

FIG. 5 is a flowchart showing an example of processing for displaying the current position in the present invention.

FIG. 6 is a flowchart showing an example of distance constant correction processing according to the present invention.

FIG. 7 is a chart showing an expansion coefficient of a tire used in another example of distance constant correction in the present invention.

FIG. 8 is an explanatory diagram showing an example of line segments in road data according to the present invention.

[Explanation of symbols]

202 ... Direction sensor, 203 ... Vehicle speed sensor, 204 ... Antenna, 205 ... GPS receiver, 206 ... Switch,
207 ... CD-ROM, 208 ... CD-ROM driver, 209 ... Display, 210 ... Controller, 8
1-86 ... Line segment.

Claims (8)

[Claims] 1. A current position calculation device mounted on a vehicle for calculating the current position of the vehicle, the direction detection means for detecting a traveling direction of the vehicle, and a part of a drive section for moving the vehicle, Based on outputs from the first speed detecting means for detecting the speed, the traveling distance calculating means for integrating the detected vehicle speeds to calculate the traveling distance of the vehicle, and the azimuth detecting means and the traveling distance calculating means. A current position calculating means for calculating and outputting the current position of the vehicle; second speed detecting means for receiving a radio wave signal from the outside and detecting the vehicle speed based on the received signal; Of the two speed detecting means, it has a speed correcting means for controlling the correction timing of the first speed detecting means according to the vehicle speed output from at least one of them and for executing the correction. Standing position calculating device. 2. The speed correction means according to claim 1, wherein the speed correction means receives the outputs from the first and second speed detection means, respectively, and outputs the first vehicle speed and the second vehicle speed output. , The ratio and the difference are calculated, and the first speed detecting means is corrected based on the second vehicle speed output while the value is within the predetermined range. Current position calculation device. 3. The speed correction means according to claim 1, wherein the speed correction means receives outputs from the first and second speed detection means, respectively, and outputs the first vehicle speed and the second vehicle speed. A current position calculating device, characterized in that the first speed detecting means is corrected on the basis of a second vehicle speed output while at least one of them is equal to or more than a predetermined value. 4. The speed correction means according to claim 1, wherein the speed correction means receives outputs from the first and second speed detection means, respectively, and outputs the first vehicle speed and the second vehicle speed. A current position calculating device characterized by calculating at least one change and correcting the first speed detecting means based on a second vehicle speed output while the value is within a predetermined value. . 5. The method according to claim 1, wherein the second speed detecting means is a GPS receiving device that detects a speed of the vehicle by a GPS signal, and the first speed detecting means is a vehicle. A rotation speed detecting means for detecting the rotation speed of the transmission output shaft or a member rotating in conjunction therewith, and a vehicle speed calculation for calculating the vehicle speed by multiplying the rotation speed by a preset traveling distance constant. And a means for correcting the traveling distance constant,
A current position calculating device, characterized in that the first speed detecting means is corrected. 6. The speed correction means according to claim 5, further receiving a DOP value output from the GPS receiving device or a value that changes in conjunction with the DOP value, and outputting the value while the value is within a predetermined range. Done second
A current position calculating device which corrects the first speed detecting means on the basis of the vehicle speed. 7. A speed correction device for correcting a speed detection means mounted on a vehicle, wherein the first speed detection means is mounted on a part of a drive section for moving the vehicle and detects the vehicle speed. And a second speed detecting means for receiving a radio wave signal from the outside and detecting the vehicle speed based on the received signal, which are mounted on the first and second speed detecting means. A speed correction device which controls the correction timing of the first speed detection means and executes the correction in accordance with the vehicle speed output from at least one of them. 8. A navigation device mounted on a vehicle for calculating and displaying a current position of the vehicle, the azimuth detecting means for detecting a traveling azimuth of the vehicle, and a part of a drive unit for moving the vehicle, Based on outputs from the first speed detecting means for detecting the speed, the traveling distance calculating means for integrating the detected vehicle speeds to calculate the traveling distance of the vehicle, and the azimuth detecting means and the traveling distance calculating means. , A current position calculation means for calculating and outputting the current position of the vehicle, a display means for displaying the calculated current position of the vehicle on a map showing the surrounding area, and a data concerning the map displayed by the display means Storage means, a second speed detecting means for receiving a radio signal from the outside, and detecting the vehicle speed based on the received signal, and at least one of the first and second speed detecting means. Depending on the vehicle speed output from the one, to control the correct timing of the first speed detecting means, a navigation system characterized in that it comprises a speed correction means for performing a correction.