1. Brief Introduction of Various Vehicle Navigation Instruments
Various vehicle-borne navigators have the function of GPS Global Satellite Positioning System, which enables you to know your exact position whenever and wherever you drive your car. Vehicle navigation has the functions of automatic voice navigation, best path search and so on. It enables you to travel freely and smoothly. The integrated functions of office and entertainment make you travel easily and efficiently. General vehicle navigation functions include DVD player, radio reception, Bluetooth hands-free, touch screen, selection function, intelligent track reversal, tire pressure detection function, virtual six discs, background control function!
Classification by vehicle type navigation:
1. DVD Navigation for Special Purpose Vehicle: A Machine for Special Purpose Vehicle (Most of them need to dismantle the original CD)
2. General-purpose type: frame can be refitted to various types of vehicles
3. Separator: Special navigation subdivision products for special vehicles. DVD navigation products will be upgraded without dismantling CD and other parts of the original vehicle.
Classification by functional navigation:
1. Traditional Handwritten Navigation
2. Voice-controlled navigation: 
1) Actual secretarial services for voice-controlled navigation;
A. Bluetooth one-click voice-controlled navigation
Advantages: Direct use of mobile Bluetooth and vehicle navigation host connection, Bluetooth first connection, the subsequent automatic connection. The signal is stable and the quality is reliable.
B. Voice-controlled navigation with external communication box;
Disadvantages: With an additional communication box, its signal receiving module and thousands of Yuan mobile phone signal receiving module are incomparable. When the signal is not good, the mobile phone has a signal and the vehicle navigation does not necessarily have a signal, causing more customer complaints. In addition, it is very troublesome to add a communication box and a telephone card to Bluetooth one-button pass.
2) Man-machine conversation voice-controlled navigation;
Disadvantage: Speech recognition software recognition rate is not high;
2. Detailed description of functional modules of the system
GPS navigation satellite accurate positioning, optimal path search, automatic voice prompt.
Navigation mode has multiple purpose input, more than five customization modes of path retrieval, site setting mode and map positioning mode.
National Map provides thousands of electronic maps of cities throughout the country, and provides the latest map support. Navigation is more accurate so that you can travel unimpeded.
Path planning provides the path planning of starting and destination, and sets the functions of passing and avoiding.
The voice prompt is cordial and real voice prompt, and the road name is broadcast automatically during driving. Music appreciation, audio-visual enjoyment, relieve fatigue.
Document management has powerful resource management function.
The 4-position principle GPS is composed of 24 working satellites, which are located at the altitude of 20200 km above the surface, and are evenly distributed on six orbital planes (4 in each orbital plane) with an orbital inclination of 55 degrees. In addition, there are four active backup satellites in orbit. The distribution of satellites enables more than four satellites to be observed anywhere and at any time in the world, and the geometric images with good positioning accuracy can be maintained. This provides global navigation capabilities that are continuous in time.
Because the position of the satellite is precise, in GPS observation, we can get the distance between the satellite and the receiver. Using the distance formula in three-dimensional coordinates and three satellites, we can form three equations to solve the position of the observation point (X, Y, Z). Considering the error between the satellite clock and the receiver clock, there are actually four unknowns, X, Y, Z and clock difference. Therefore, it is necessary to introduce the fourth satellite and form four equations to solve them, so as to obtain the longitude, latitude and elevation of the observation points.
In fact, the receiver can lock more than four satellites. At this time, the receiver can be divided into several groups according to the constellation distribution of the satellite, each group of four, and then select the group with the smallest error for positioning by the algorithm, so as to improve the accuracy.
Because of the errors of satellite orbit and clock, the influence of atmosphere troposphere and ionosphere on signal, and the 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 station) for GPS observation. The known precise coordinates of the reference station are used to compare with the observed values, thus a correction number is obtained and released. After receiving the correction, the receiver compares with its own observation value, eliminates most of the errors and obtains a more accurate position. Experiments show that the positioning accuracy can be improved to 5 meters by using differential GPS.
5. Vehicle navigation system consists of navigation host and navigation display terminal. The built-in GPS antenna receives data from at least three of the 24 GPS satellites around the earth, thereby determining the current position of the car. By matching the position coordinates determined by GPS satellite signals with the electronic map data, the navigation host can determine the exact position of the vehicle in the electronic map.
On this basis, many functions will be realized, such as driving navigation, route recommendation, information inquiry, playing AV/TV and so on. Drivers only need to watch the screen on the display and listen to voice prompts to control the remote control in hand to achieve the above functions, thus driving easily and freely.