Implementation principle and function analysis of vehicle GPS positioning system

What is a car GPS positioning system? Simply put, when a GPS positioning system terminal is used for vehicle positioning through hardware and software, we call it a car GPS positioning system (what is GPS). Then how is it achieved, what is its implementation principle (GPS principle), and what function? Xiaobian collects and organizes the data, and simply summarizes the knowledge of the car GPS positioning system. Let us first understand How does the car GPS positioning system work?

This article refers to the address: http://

Implementation of Vehicle GPS Positioning System

It is not possible to locate the light here. It is also necessary to transmit this positioning information to the alarm center or the holder of the car GPS positioning system. We call it a third party. Therefore, the GPS positioning system also includes GSM network communication (mobile communication). The satellite positioning information is sent to the third party through the GSM network by means of short message, and the short message is interpreted by the microcomputer to display the position of the vehicle on the electronic map, thus realizing the vehicle GPS positioning system.

At the same time, the corresponding detection sensor is installed on the vehicle, and the GSM network communication function of the vehicle GPS positioning can also be used to send the burglar alarm information to the third party, or the alarm phone and the short message can be directly sent to the owner's mobile phone to complete the vehicle. GPS anti-theft alarm. It can be seen here that the GSM network part of the car GPS positioning is actually a smart phone, which can communicate with the third party, and can also be robbed of the vehicle, the driver is robbed, kidnapped and other information is sent to the third party, so the car GPS Positioning is positioning, anti-theft, anti-robbery.

Overview of the principle of car GPS positioning system

The basic principle of the GPS navigation system is to measure the distance between the satellite at the known location and the receiver of the user, and then combine the data of multiple satellites to know the specific location of the receiver. To achieve this, the position of the satellite can be detected in the satellite ephemeris based on the time recorded by the onboard clock. The distance from the user to the satellite is recorded by the satellite signal to the time elapsed by the user, and then multiplied by the speed of light (due to the interference of the ionosphere of the atmosphere, this distance is not the true distance between the user and the satellite, but Pseudorange (PR): When GPS satellites work normally, they will continuously transmit navigation messages with pseudo-random codes (referred to as pseudo-codes) consisting of 1 and 0 binary symbols. There are two kinds of pseudo-codes used by GPS systems. Civil C/A code and military P (Y) code.

The C/A code frequency is 1.023MHz, the repetition period is one millisecond, the code spacing is 1 microsecond, which is equivalent to 300m; the P code frequency is 10.23MHz, the repetition period is 266.4 days, and the code spacing is 0.1 microsecond, which is equivalent to 30m. The Y code is formed on the basis of the P code, and the security performance is better. The navigation message includes information such as satellite ephemeris, working conditions, clock correction, ionospheric delay correction, and atmospheric refraction correction. It is demodulated from the satellite signal and transmitted on the carrier frequency with 50b/s modulation. The navigation message contains 5 sub-frames per main frame and is 6s long. The first three frames are each 10 words; they are repeated every 30 seconds and updated every hour. The last two frames total 15000b.

The contents of the navigation message mainly include telemetry code, conversion code, and the first, second, and third data blocks, and the most important one is the ephemeris data. When the user receives the navigation message, the satellite time is extracted and compared with his own clock to know the distance between the satellite and the user, and then the satellite ephemeris data in the navigation message is used to calculate the position of the satellite when transmitting the message. The user's position and speed information in the WGS-84 geodetic coordinate system can be known.

It can be seen that the role of the satellite part of the GPS navigation system is to continuously transmit navigation messages. However, since the clock used by the user's receiver is not always synchronized with the satellite onboard clock, in addition to the user's three-dimensional coordinates x, y, z, a Δt, that is, the time difference between the satellite and the receiver is introduced as an unknown number. Then use four equations to solve the four unknowns. So if you want to know where the receiver is, you must be able to receive at least 4 satellite signals.

The GPS receiver can receive time information accurate to the nanosecond level that can be used for timing; a forecast ephemeris used to predict the approximate location of the satellite in the next few months; and a broadcast ephemeris used to calculate the satellite coordinates required for positioning. The accuracy is from a few meters to tens of meters (different satellites, changing at any time); and GPS system information, such as satellite status.

The GPS receiver measures the distance from the satellite to the receiver. It is called pseudorange because it contains the error of the receiver satellite clock and the atmospheric propagation error. The pseudorange measured by the 0A code is called the UA code pseudorange, and the precision is about 20 meters. The pseudorange measured by the P code is called the P code pseudorange, and the precision is about 2 meters.

The GPS receiver decodes the received satellite signal or uses other techniques to remove the information modulated on the carrier and recover the carrier. Strictly speaking, the carrier phase should be referred to as the carrier beat frequency phase, which is the difference between the received satellite signal carrier phase affected by the Doppler shift and the phase of the receiver local oscillator generated signal.

Generally, the epoch time determined by the receiver clock is measured, and the tracking of the satellite signal is kept, and the phase change value can be recorded, but the initial phase values ​​of the receiver and the satellite oscillator at the start of observation are unknown. The phase integer of the epoch is also unknown, that is, the ambiguity of the whole week can only be solved as a parameter in data processing. The accuracy of the phase observation is as high as millimeter, but the premise is that the whole-circumference ambiguity is solved. Therefore, the phase observation value can be used only when the relative positioning is performed and there is a continuous observation value, and the positioning accuracy is better than the meter level. Phase observations can be used.

According to the positioning method, GPS positioning is divided into single point positioning and relative positioning (differential positioning). Single point positioning is a way to determine the position of the receiver based on the observation data of a receiver. It can only be measured by pseudo-range observation and can be used for rough navigation and positioning of vehicles and ships. Relative positioning (differential positioning) is a method of determining the relative position between observation points based on observation data of two or more receivers. It can use both pseudo-range observation and phase observation. Geodesy or engineering measurement should be performed. Phase observations are used for relative positioning.

The GPS observations include errors such as the clock difference of the satellite and the receiver, the atmospheric propagation delay, and the multipath effect. They are also affected by the satellite broadcast ephemeris error during the positioning calculation. Most of the common errors are caused by relative positioning. Offset or weaken, so the positioning accuracy will be greatly improved. The dual-frequency receiver can offset the main part of the ionospheric error in the atmosphere according to the observation of two frequencies. When the accuracy is high and the distance between receivers is far away (the atmosphere is obviously different) ), should use dual-frequency receiver.

Car GPS positioning system function

(1) Vehicle tracking function

GPS and electronic maps can be used to display the actual position of the vehicle in real time, and can be arbitrarily enlarged, reduced, restored, and changed; can be moved with the target to keep the target on the screen; multi-window, multi-vehicle, multi-screen Track at the same time. Use this feature to track and transport important vehicles and goods.

(2) Information inquiry function

Provide users with zc main objects, such as tourist attractions, hotels, hospitals and other databases, users can display their location on the electronic map. At the same time, the monitoring center can use the monitoring console to query the location of any target in the area, and the vehicle information will be displayed in digital form on the electronic map of the control center.

(3) Travel route planning and navigation functions

Providing travel route planning is an important auxiliary function of car navigation systems, including automatic route planning and manual line design. The automatic route planning is determined by the driver to determine the starting point and destination. The computer software automatically designs the optimal driving route according to the requirements, including the fastest route, the simplest route, and the calculation of the route with the least number of highway sections. The artificial line design is automatically created by the driver according to his destination design start point, end point and route point. After the route is planned, the display can display the design route on the electronic map, and simultaneously display the car running path and operation method.

(4) Emergency assistance function

Through the GPS positioning and monitoring management system, emergency assistance can be provided to vehicles in danger or accidents. The electronic map of the monitoring station displays the help information and alarm targets, plans the optimal assistance plan, and alerts the on-duty personnel to the emergency treatment with the alarm sound and light.

(5) Traffic command function

The command center can monitor the running condition of the vehicles in the area and make reasonable dispatch of the monitored vehicles. The command center can also talk to the tracked target at any time to implement management.

to sum up

With the continuous development of automotive electronic application technology, the market demand for automotive products is gradually increasing. The vehicle GPS positioning system is one of them. Through the above introduction of its implementation method and functional principle, we should have a GPS positioning system for the vehicle. A simple understanding.

Wireless Charger

Wireless Smartphone Charger,Wireless Charger,Android Wireless Charger,Apple Iphone Wireless Charger

Dongguan baiyou electronic co.,ltd , https://www.dgbaiyou.com

Posted on