JPH0754351B2 - Data processing method of GPS receiver - Google Patents

Description

TECHNICAL FIELD The present invention relates to a global positioning satellite system (Global Positioni
ng System, hereinafter abbreviated as GPS), the present invention relates to a method of processing received data of a GPS receiving device which outputs current position data of a vehicle.

BACKGROUND ART In recent years, a vehicle-mounted navigation device that guides a vehicle to a predetermined destination by storing map information in a memory and reading the map information from the memory on a display device together with the current location of the vehicle has been researched and developed. Has been done.

A detection means for detecting the current position of the vehicle is indispensable to such a navigation device, and the above-mentioned GPS is used as this detection means, for example. This system is said to be able to receive radio waves emitted from multiple satellites and measure the current position of the vehicle with a maximum accuracy of about 20 m.

However, the measurement accuracy of such a system will fluctuate depending on the position of the satellite, the perturbation of the satellite, the state of the ionosphere, etc.Therefore, if the data received by the GPS receiver is used as it is, the desired measurement accuracy will be obtained. It is not possible, and the current position of the running vehicle changes from moment to moment. Therefore, it is desirable to be able to accurately detect the current position of the vehicle in response to this change.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and enables more accurate current position detection of a vehicle by increasing the reliability of the current position data obtained by a GPS receiver.
An object is to provide a data processing method of a GPS receiving device.

A data processing method for a GPS receiving device according to the present invention is a data processing method for a GPS receiving device which is mounted on a vehicle, which measures the current position of the vehicle based on a global positioning satellite system and sequentially outputs measured current position data. Then, an average value and a standard deviation of the measured current position data are obtained while the vehicle is stopped, and when the standard deviation is within a predetermined value, the average value is used as the current position data of the vehicle.

Example Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an in-vehicle navigation device to which a data processing method of a GPS receiving device according to the present invention is applied. In the figure, 1 is geomagnetism (earth magnetic field)
A geomagnetic sensor for outputting the azimuth data of the vehicle based on the above, 2 is an angular velocity sensor for detecting the angular velocity of the vehicle, 3 is a mileage sensor for detecting the moving distance of the vehicle, 4 is latitude and longitude information, etc. It is a GPS receiving device for detecting the current position of the vehicle from the
Is supplied to the system control 5.

The system controller 5 receives the outputs of the respective sensors (devices) 1 to 4 as an input, performs an A / D (analog / digital) conversion, and the like, and performs various image data processing and sequentially sends from the interface 6. A CPU (central processing circuit) 7 that calculates the amount of movement of the vehicle based on the output data of each sensor (device) 1 to 4, and this C
A ROM (read only memory) 8 in which various processing programs of the PU 7 and other necessary information are written in advance, and a RAM (random access memory) in which information necessary for executing the program is written and read. ) 9
And a so-called CD-ROM, I card, etc., and a recording medium 10 on which digitized (numerical) map information is recorded.
, A graphic memory 11 composed of V-RAM (Video RAM) and the like, and graphic data such as a map sent from the CPU 7 are drawn in the graphic memory 11 and are CR as an image.
It is composed of a graphic controller 13 for controlling the display 12 such as T. The input device 14 is composed of a keyboard and the like, and issues various commands to the system control 5 by key input by the user.

Next, the basic procedure executed by the CPU 7 will be described with reference to the flowchart of FIG.

The CPU 7 first initializes to execute the program (step S1), and thereafter determines whether or not the current position of the vehicle is set (step S1).
2). If the current location has not been set, the current location setting routine is executed (step S3), for example, the current location is set by key input on the input device 14. next,
The mileage is set to zero (step S4), and then it is determined whether or not there is a key input from the input device 14 (step S4).
Five).

If there is no key input, the map around the current location is displayed on the display 12, and the current position and direction of the vehicle are displayed on this map, for example, by the vehicle mark, and when the vehicle moves, the map scrolls with the movement. When the vehicle position is likely to exceed the range of the map data currently on the graphic memory 11, the necessary map data is read from the recording medium 10 and displayed on the display 12 (step S6).

If there is a key input, each routine of resetting the current location (step S7), correcting the sensor (step S8), setting the destination (step S9) and enlarging / reducing the map (step S10) is executed according to the input data. To do.

Further, the CPU 7 constantly calculates the heading of the vehicle based on the output data of the geomagnetic sensor 1 and the angular velocity sensor 2 at constant time intervals as shown in FIG. 3 by the interrupt processing by the timer (steps S11, S12).

By the way, GPS is a system that receives radio waves emitted from satellites and obtains the current position of a vehicle as an absolute position (latitude, longitude) on the earth. As mentioned above, this system is said to be able to measure the current position of the vehicle with a maximum accuracy of about 20 m, but the measurement accuracy varies depending on the satellite position, satellite perturbation, ionospheric conditions, etc. Resulting in.

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

As shown schematically in FIG. 4, 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. Composed of each satellite S ₁
~ S ₄ are 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 for receiving signals from the antennas A _{1 to} A ₄ and a transmitter for emitting various information signals to the user P, and the user P is a satellite S. Each is equipped with an oscillator that receives signals from _{1 to} S ₄ .

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 timing is measured with the reception signal, the propagation time of the radio wave between the transmission and reception points 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 users three satellites S ₁ in view (受可functional area) of P, S _2, S _3, each of the satellite S _1, S _2, ranging signal by clock S ₃ are synchronized with each other It is assumed that the satellites are being transmitted and the positions of the satellites S ₁ , S ₂ , and S _{3 at} the time of reception have been accurately obtained. Reception point P
By measuring the reception time of these signals at
The distances between S ₁ , S ₂ , S ₃ and the receiving point P are obtained, and the position of the user P can be obtained as the intersection of three spherical surfaces centered on the satellites S ₁ , S ₂ , 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. Further, in this system, since the measurement accuracy varies including the position error of the satellites S _{1 to} S _{4 and} the ranging error due to the state of the ionosphere, the signals emitted from the satellites S _{1 to} S ₄ to the user P are Data of a deterioration coefficient (Geometrical Dilution Of Precision, hereinafter abbreviated as GDOP), which is a coefficient indicating the magnitude of the distance measurement error, is included.

The table below shows an example of the types and magnitudes of distance measurement errors that have been published.By multiplying these numbers by GDOP, the position when the user actually uses this system is shown. The detection accuracy can be calculated.

Therefore, in the present invention, in order to further improve the reliability of the reception data of the GPS receiving device 4, data processing necessary for the transmission data of the GPS receiving device 4 is performed while the vehicle is stopped, and statistical processing is performed. Is easy to do.

Next, the procedure of the method for processing the received data of the GPS receiving device 4 according to the present invention, which is executed by the CPU 7, will be described with reference to the flowchart of FIG.

The CPU 7 first determines whether or not the vehicle is stopped (step S21). If it is stopped, whether the data output from the GPS receiving device 4, that is, the measured current position data (hereinafter, referred to as GPS data) indicating the current position of the vehicle measured by the method described above is valid or not. Is determined (step S22). This judgment is made using the GDOP (degradation coefficient) of GPS data. This 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 location.

If it is determined in step S22 that the GPS data is invalid, the process ends without doing anything, and if it is determined that the GPS data is valid, the count value of the data counter is first set to zero (step S23), and then GPS receiver 4 when the vehicle is stopped
It is determined whether or not a predetermined number of GPS data have been input from (steps S24, S25). If a predetermined number of GPS data have been input, the average value of these data is calculated and at the same time the standard deviation is calculated (step S26), and the standard deviation is the predetermined value σs.
It is determined whether it is within the range (step S27). If the standard deviation is within the predetermined value σs, the average value is stored in the RAM 9 as the current position data of the vehicle (step S28) and used for subsequent calculation of the current position. Further, at this time, the current location recognition processing executed based on the map data is also performed.

In the process of recognizing the present location, the distance error caused by the detection error of the traveling distance sensor 3 or the digitizing error of the map data is calculated based on the map data every time the vehicle travels a certain distance. By detecting a position on a distant road and setting the detected position as the current position, a process for always accurately recognizing the current position of the vehicle is performed. For the specific method of this location recognition process,
It has already been proposed by the applicant in Japanese Patent Application No. 61-156883.

As described above, while the vehicle is stopped, necessary processing is performed on the GPS data to obtain the current position data, so that the current position of the vehicle can be accurately obtained from the current position data.

As described above, according to the present invention, while the vehicle is stopped, the average value and the standard deviation of the measured current position data measured and output by the GPS receiver are obtained, and the standard deviation is a predetermined value. It is possible to increase the reliability of the measured current position data obtained by the GPS receiving device by determining that the measured current position data is valid data by determining the average value as the vehicle current position data when Therefore, the current position of the vehicle can be detected more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a vehicle-mounted navigation device to which the data processing method for a GPS receiving device according to the present invention is applied, and FIGS. 2 and 3 show the basic procedure executed by the CPU in FIG. The flowchart shown in FIG. 4, FIG. 4 is a schematic explanatory view for explaining the principle of GPS, and FIG. 5 is a flowchart showing the procedure of the data processing method of the GPS receiving apparatus according to the present invention, which is executed by the CPU in FIG. Explanation of symbols of main parts 1 ... Geomagnetic sensor, 2 ... Angular velocity sensor 4 ... GPS receiver 5 ... System controller 7 ... CPU, 10 ... Recording medium 12 ... Display, 14 ... Input device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsuhiko Fukushima 42610 Hanazono, Tokorozawa-shi, Saitama Pioneer Co., Ltd. Tokorozawa factory (56) Reference JP-A-62-298786 (JP, A)

Claims (1)

[Claims] 1. A data processing method for a GPS receiving device, which is mounted on a vehicle and measures the current position of the vehicle based on a global positioning satellite system and sequentially outputs the measured current position data, wherein the vehicle is stopped. A data processing method for a GPS receiving apparatus, wherein an average value and a standard deviation of the measured current position data are obtained, and the average value is used as the current position data of the vehicle when the standard deviation is within a predetermined value.