“With the popularization of various vehicles such as automobiles, the demand for vehicle navigation devices has become increasingly strong. as in-vehicle equipment. Not only reliable performance, but also portability, low power consumption, and low price. And the design scheme of GPS navigation terminal, which adopts the embedded system based on ARM microprocessor and GPS module, can well meet the requirements of this system. To this end, this paper introduces the software and hardware structure and design method of a terminal that uses ARM9 development board and GPS module to realize GPS navigation function.
With the popularization of various vehicles such as automobiles, the demand for vehicle navigation devices has become increasingly strong. as in-vehicle equipment. Not only reliable performance, but also portability, low power consumption, and low price. And the design scheme of GPS navigation terminal, which adopts the embedded system based on ARM microprocessor and GPS module, can well meet the requirements of this system. To this end, this paper introduces the software and hardware structure and design method of a terminal that uses ARM9 development board and GPS module to realize GPS navigation function.
2 GPS navigation system structure
The GPS global positioning and navigation system introduced in this paper can be divided into five parts: embedded main control module, GPS module, Display module, expansion module and power supply module according to its functions.
The embedded main control module is based on the S3C2440 processor and is mainly responsible for the response, processing and control of the GPS navigation module data. In hardware, the main control module is an embedded development board, including touch LCD interface circuit, SD card interface circuit, FLASH, SDRAM, etc. In software, the embedded Linux system should be run on the main control module. The main function of the embedded Linux operating system is to manage the program module process and schedule the process.
The GPS module is mainly used to receive navigation satellite data and send it to the main control module in a specific format. The Display module can choose 3.5-inch TFT LCD with touch screen, which is mainly used to interact with users. The expansion module mainly refers to the SD card. The power supply module mainly provides power for the normal operation of the system. Figure 1 shows the structure of the system.
3 Extraction of GPS data
The output sentences of the GR-87 GPS module follow the NMEA-0183 standard. The standard sentences all start with “$” and end with “CR” and “LF”. “$” is followed by a 5-character address, the first two characters are the sender identification code (“GP” for GPS), and the last three characters are the sentence name. The data in the positioning information is divided by “,”. The GPS module can generally output sentences in NMEA-0183 format once per second. In a navigation system, generally only time, date, latitude and longitude, and speed are needed. And because the RMC statement completely contains the above information required by the system, so. Only need to extract the RMC statement. Figure 2 shows the specific process of extracting GPS data.
4 Implementation of Navigation Map
After obtaining the positioning information such as latitude and longitude, it is also necessary to visually display them on an Electronic map or other display media, so as to truly play a role in navigation. In order to accurately display it on the electronic map, it needs to be transformed with a certain algorithm, that is, the map matching algorithm.
In general, the basic idea of map matching is to match the GPS track of the vehicle with the vectorized road segment objects on the map, so as to find the road currently traveling, and project the current GPS positioning point on the road.
The key to map matching is to determine the matching points, and the projection method can be used to find the matching points during design. The basic idea of the projection method is to determine the matching point with the smallest value as the projection based on the distance from the point to the line, and process it with the nearest neighbor method, and then filter out the wrong matching points by setting the threshold to obtain the preliminary result, thus completing the point to line. match.
The specific implementation method is to preprocess the road layer first, then convert the road into a polyline segment, find the current road, then project the current location point on the road, and then find a line segment in the road layer closest to the location point, and then Calculate the point with the shortest distance from the point to the line, and finally find the road within the error range in each layer.
The basic process code of its algorithm is as follows:
The realization of the navigation map can be realized by using the embedded graphical interface tool Qt embedded. The graphical interface is a human-computer interaction interface, and the user can understand the navigation information through the screen, and can also directly operate the touch screen to operate the system, such as zooming in and out of the map, viewing positioning information, and the like.
Because the ARM processor has the characteristics of low power consumption and high performance, it can be widely used in various portable electronic products. Based on the existing electronic products, this design expands the GPS navigation function through an external GPS module, which can save costs for users without losing too much portability. To this end, the author hopes to use the combination of ARM development board and GPS module to realize the method of GPS navigation function, which can provide a reference for smart devices to expand GPS function.
The Links: LQ150X1LGN2A NL6448AC20-02