Car navigation

With the help of GPS global positioning system, you can know yourself anytime and anywhere while driving.

The exact location. Its automatic voice navigation, best path search and other functions make you fast all the way, and the integrated office entertainment function makes you travel easily and efficiently!

GPS positioning principle:

Twenty-four GPS satellites orbit the earth at a height of 12000 km from the ground, with a period of 12 hours, so that more than four satellites can be observed at any time and at any point on the ground.

Because the position of satellite is accurately known, we can get the distance from satellite to receiver in GPS observation. Using three-dimensional coordinates and the distance formula in three satellites, three equations can be formed to solve the position (x, y, z) of the observation point. Considering the error between satellite clock and receiver clock, there are actually four unknowns, X, Y, Z and clock difference, so it is necessary to introduce a fourth satellite to form four equations to solve, so as to get the latitude, longitude and elevation of the observation point.

In fact, receivers can often lock on more than four satellites. At this time, the receiver can be divided into several groups with four satellites in each group according to the constellation distribution of satellites, and then the group with the smallest error can be selected by algorithm to locate, which improves the accuracy.

Due to the error of satellite orbit and satellite clock, the influence of atmospheric troposphere and ionosphere on signals, and artificial SA protection policy, the positioning accuracy of civil GPS is only 100 meters. In order to improve the positioning accuracy, differential GPS(DGPS) technology is widely used to establish a reference station (differential substation) for GPS observation. By comparing the precise coordinates of the known reference station with the observed values, a correction number is obtained and released to the public. After receiving the correction number, the receiver compares it with its own observation value to eliminate most errors and get a more accurate position. Experiments show that the positioning accuracy can be improved to 5 meters by using differential GPS.

Vehicle navigation system is mainly composed of navigation host and navigation display terminal. The built-in GPS antenna will receive data information from at least three of the 24 GPS satellites orbiting the earth, so as to determine the current position of the car. By matching the position coordinates determined by the navigation host through GPS satellite signals with the electronic map data, the accurate position of the car in the electronic map can be determined.

On this basis, it will realize many functions, such as driving navigation, route recommendation, information inquiry, playing AV/TV and so on. The driver only needs to look at the picture on the display screen, listen to the voice prompt and manipulate the remote control in his hand, so as to realize the above functions and drive easily.

Automobile GPS navigation system consists of two parts:

Part of it consists of GPS receiver and display equipment installed in the car; The other part is composed of computer control center, and the two parts are connected by positioning satellites.

The computer control center is authorized by the motor vehicle management department and is responsible for observing the dynamics and traffic conditions of designated monitoring vehicles within its jurisdiction at any time. Therefore, the whole car navigation system has at least two functions: first, the car trail monitoring function, as long as the coded GPS receiver is installed on the car, the car can indicate its position through the electronic map of the computer control center no matter where it travels; The other is the driver's guidance function. Car owners can store electronic maps of traffic routes in various areas on floppy disks. As long as the floppy disk is inserted into the vehicle receiving device, the position and current traffic state of the vehicle will be displayed on the display screen immediately. You can not only enter the destination you want to go to, but also work out the best driving route in advance. You can accept the instructions from the computer control center to choose the driving route and direction of the vehicle.

Four elements of vehicle-mounted satellite navigation system;

Geosynchronous satellites located above the earth were originally used for military and aviation navigation. The U.S. government relaxed the restrictions on the use of synchronous satellites in the 1980s, which opened up a new world for its wide adoption. Subsequent commercial communication satellites greatly improved the accuracy and coverage of communication satellites.

Since the advent of highways, there have been maps to guide people. However, as a guide for people, maps often become a source of tension between people. Because the printed map often can't keep up with the changes of the street, it is difficult to identify, which will lead the driver to blame the people in the car next to him for not reading the map and not providing accurate instructions. Therefore, a satellite navigation system that can accurately and timely navigate and locate cars by using satellite signals at high altitude has become priceless.

In recent years, the development of car navigation system is very rapid. At present, people can not only choose the navigation system as an optional configuration when buying a new car, but also install the device on an existing car, and even configure a mobile satellite navigation system to put in that car when driving it, or take it to have a picnic or climb a mountain.

The satellite navigation system for guiding drivers has the following four important factors: satellite signal, signal reception, signal processing and map database.

Satellite signal:

Car satellite navigation system needs to rely on global positioning system (GPS) to determine the position of the car. Basically, GPS needs to know the latitude and longitude of the car. In some special cases, GPS needs to know the altitude to locate accurately. With these three sets of data, the accuracy of GPS positioning can often reach 2 ~ 3 meters.

Because GPS requires the vehicle navigation system to work in the direct line of sight of synchronous satellites, tunnels, bridges or high-rise buildings will block this direct line of sight and make the navigation system unable to work. Moreover, the navigation system uses triangles and geometric laws to calculate the position of the car, so the car can only be determined if it is at least under the sight of three synchronous satellites at the same time. The more synchronous satellites in the direct line of sight of the navigation system, the more accurate the positioning. Of course, most synchronous satellites are above densely populated cities, so when you are far away from cities, the navigation system will not work well or even at all.

Signal reception:

The working principle of GPS system is to analyze the signals received from synchronous satellites. Projected on a vertical plane, these signals can be visually represented as inverted funnels. When the lower half of these funnels overlap, the GPS analysis program can calculate the coordinates of the car's location. A device similar to a gyroscope is used for the navigation of an airplane or a ship, and can continuously provide the position of a car when the car is running. However, when the satellite signal is interrupted, the data provided by the speedometer is used to fill in the blank and record the driving time.

Signal processing:

The signal received by GPS and the information provided by speedometer will be provided to the vehicle navigation system through the receiver, which will be analyzed and processed by the software system and superimposed on the stored map.

Map database:

When the coordinate information provided by GPS is superimposed on the electronic map, the driver can see his current position and future direction. This last link is called surveying and mapping, and it is also the most important link in the car navigation system. Without a map, the navigation system has no direction.

There are many channels for the map database of car navigation system, the most important of which is the block database provided by city government agencies. For a good car navigation system, the quantity and accuracy of maps and the timeliness of data are very important. No matter how accurate the coordinate position provided by GPS is, if your navigation system can't provide a map of your area, or the provided map is wrong, your system can be said to be worthless. Therefore, when purchasing a vehicle-mounted satellite navigation system, we should pay attention to the following matters:

First, check the accuracy of the test system. Choose one or two familiar roads or newly opened hotels to see if the system can accurately display the location of the car. Because streets and road sections are always changing, your system must also provide regular update services.

Second, consider the storage capacity of the system. In America, if you want to keep all the maps of the whole country, you need at least three CDs. Therefore, the car navigation system must also have a correspondingly large hard disk memory.

Third, image display. The image display of the car navigation system can be installed on the dashboard of the car, and can also be projected on the screen of a notebook computer or even a PDA. In order to adapt to different weather and lighting conditions, the image display screen must have sufficient brightness, sufficient size and good resolution.

Classification of automobile navigation system;

GPS vehicle application systems are generally divided into two categories: vehicle tracking system and vehicle navigation system. They are completely different in function, one is vehicle anti-theft and the other is vehicle autonomous navigation. Because the signal of "only receiving but not sending" is a major feature of GPS receiving system, the GPS tracking system for anti-theft is to provide a solution for collecting the use fee for GPS car anti-theft instrument with the help of communication network and government supporting system. On the other hand, the car navigator can grasp its position and destination in time by receiving satellite signals and cooperating with electronic map data. The autonomous navigation mode does not charge any usage fees, and users can selectively purchase map data according to their own needs.

GPS technology uses GPS satellite signal reception, which can continuously receive the data parameters sent by the satellite for 24 hours and calculate the received three-dimensional position, three-dimensional direction, movement speed and time information. By receiving satellite signals and cooperating with electronic map data, the car navigator can grasp its position and destination in time. The autonomous navigation mode does not charge any usage fees, and users can selectively purchase map data according to their own needs. When the user installs the car GPS in the car, no matter which city, town or suburb the user is in, we can find the restaurant or the nearest gas station in an instant.

The concept of global positioning system;

Global Positioning System (GPS) is a new generation of space satellite navigation and positioning system jointly developed by the United States Army, Navy and Air Force in 1970s. Its main purpose is to provide real-time, all-weather and global navigation services for land, sea and air, and it is also used for some military purposes such as intelligence gathering, nuclear explosion monitoring and emergency communication. It is an important part of America's global dominant strategy. After more than 20 years of research and experiments, it cost 30 billion dollars. By1March 1994, 24 GPS satellite constellations with global coverage of 98% had been deployed.

The global positioning system consists of three parts: (1) the ground control part, which consists of the main control station (responsible for managing and coordinating the work of the whole ground control system), the ground antenna (injecting the search message into the satellite under the control of the main control station), the monitoring station (automatic data acquisition center) and the communication auxiliary system (data transmission); (2) Space part, which consists of 24 satellites and distributed on 6 trajectory planes; (3) User equipment is mainly composed of GPS receiver and satellite antenna.

The main features of GPS are: (1) all-weather; (2) Global coverage; (3) The three-dimensional constant speed timing accuracy is high; (4) Fast, time-saving and efficient; (5) It has a wide range of uses and diverse functions.

Main uses of GPS: (1) land applications, mainly including vehicle navigation, emergency response, atmospheric physical observation, geophysical resource exploration, engineering survey, deformation monitoring, crustal movement monitoring, municipal planning control, etc. (2) Marine applications, including the determination of the best navigation route of ocean-going ships, real-time ship dispatching and navigation, maritime rescue, marine treasure exploration, hydrogeological investigation, offshore platform positioning, sea level fluctuation monitoring, etc. (3) Aerospace applications, including aircraft navigation, attitude control of aerial remote sensing, orbit determination of LEO satellites, missile guidance, aviation rescue and manned spacecraft protection detection.

There are many kinds of GPS satellite receivers, which are divided into geodesic type, all-station type, time service type, hand-held type and integrated type according to models. According to the purpose, it is divided into vehicle, ship, airborne, satellite and missile.

After more than 20 years of practice, it has been proved that GPS system is a high-precision, all-weather and global multifunctional radio navigation, positioning and timing system. GPS technology has developed into a multi-field, multi-mode, multi-purpose and multi-mode international high-tech industry.

The latest development trend:

The latest development trend of car navigation system is to use Bluetooth wireless technology to receive signals transmitted by car GPS. In this way, the vehicle-mounted system only needs to receive and process satellite signals, and the display device is responsible for the storage of maps and the superposition of positions. So, if you already have a PDA, you only need to buy a signal receiver and drawing software. Your PDA can be used for many purposes. In fact, many mobile phones already have GPS function. If you add the overlay function of maps, you can turn them into mobile navigation systems.

Besides guiding you, car navigation system can also be used for many other purposes, such as helping you find nearby gas stations, ATMs, hotels or other shops. Some can also tell you how to avoid dangerous areas or traffic jams.

Most car navigation systems use visual display system as the interface of man-machine communication. Others provide a voice system, allowing people to talk directly with the navigation system, and remind drivers when to turn and get out of the highway by voice. Some can also provide you with a route map for your return trip, or you need to go back if you go wrong.

Some car navigation systems can also be displayed in different languages. Some can also tell you the local speed limit, road conditions and your average speed, and estimate the time to reach your destination for you.

Application example of GPS technology in navigator

The international leading brand of GPS navigator: Ahada- originated in Silicon Valley, USA, and now registered in China!

Ahada-focuses on developing advanced GPS satellite navigation portable equipment suppliers. The company's product line covers a full range of GPS portable products such as portable navigation, GPS mobile navigation and personal handheld navigation equipment.

Ahada-R&D, whose production and sales organizations are established in Silicon Valley and China respectively, brings together many world-class scientific and technological elites with many years of experience in GPS and communication fields, and realizes Ahada's leading technology and excellent quality.

The first domestic product: Ahada N 310-a cost-effective machine king (a GPS navigator model specially designed for business elites and white-collar women).

Product core functions:

1) map query

◎ You can search your destination location on the operating terminal.

◎ You can record the location information of the places you often go to and save it, or you can share it with others.

◎ Vaguely inquire about the information near one's attachment or a certain location, such as gas station, hotel, ATM, etc.

2) Route planning

◎ The ◎GPS navigation system will automatically plan the route according to the starting point and destination you set.

◎ You can set whether the planned route passes through some route points.

◎ Planning lines can be set to avoid high speed and other functions.

3) Automatic navigation

◎ Voice navigation:

Provide drivers with driving information such as turning at intersections and the status of navigation system in advance by voice, just like a guide who knows the way tells you how to drive to your destination. One of the most important functions in navigation is to let you reach your destination safely through voice prompts without looking at the operation terminal.

◎ Picture navigation:

A map will be displayed on the operation terminal, as well as the driving information of the current position, driving speed, destination distance, planned route prompt and intersection turning prompt of the car.

◎ Re-plan the route:

When you don't follow the planned route or take the wrong intersection, the GPS navigation system will re-plan a new route to your destination according to your current position.