GPS tracker module introduction and application industry

2019/5/21 9:06:07

The GPS tracker module is a GPS signal receiver that receives and demodulates the satellite's broadcast C/A code signal like a "radio" and does not send a signal, which is passive positioning.

         The information received by the GPS tracker module calculates the longitude, latitude, altitude and time correction of the receiver by calculating the pseudo-distance from each satellite by using the distance intersection method. The feature is that the point speed is fast, but The error is large. The initial positioning module requires at least 4 satellites to participate in the calculation, called 3D positioning, and 3 satellites can achieve 2D positioning, but the accuracy is not good. The GPS tracker module continuously outputs positioning information and auxiliary information in the NMEA format through the serial communication port for the recipient to select an application.

Factors affecting the accuracy of the GPS tracker module.

 

       The positioning accuracy of the GPS tracker module depends on many aspects, such as the satellite clock difference and orbit difference from the GPS tracker system, the number and geometric distribution of visible GPS tracker satellites, solar radiation, the atmosphere, and multipath effects. In addition, the same GPS tracker module will also generate different positioning errors due to antenna and feeder quality, antenna position and direction, test time period, open sky range and direction, weather, PCB design and other reasons. Even when different GPS tracker modules of the same model of the same manufacturer use the antenna splitter to test simultaneously, the amount of static drift will be different.

 GPS Tracker module

GPS tracker module positioning principle

        Roughly, ground coordinates and their regular geographic features (ie, spatial resections) are obtained by measuring the distance from the orbiting satellite (which is determined to be a known data in orbit) to the ground point. Since the position quantity in the solution equation has XYZ and the clock difference T, the number of satellites received must be greater than or equal to four.

 

In the positioning process, there are two ways to obtain the pseudorange of the satellite to the ground (that is, the distance containing the error): 1, the ranging code; 2, the carrier phase.

 

  1. The ranging code belongs to a pseudo random noise code and is a binary code sequence. The key is to measure the time difference between the transmitted signal and the received signal, obtained by atomic clock synchronization. Since the carrier carrying the ranging code is refracted while passing through the current layer, an ionospheric error is generated. Solar activity has an impact on the total electron density of the ionosphere, so this will also have an impact on GPS tracker positioning. According to our teacher, there was a time when the GPS tracker could not be used because of solar flares.

  2. If a satellite S issues a carrier model (where the carrier is used as a ranging signal), the signal propagates everywhere. At a certain instant, the signal has a phase ψR at the receiver R and ψS at the satellite S. Note that ψR, ψS referred to here are the complete carrier phase including the entire number of weeks starting from the same starting point. Then the distance between the cemetery is ρ=λ(ψS-ψR).

    It can be seen from the above that if the corresponding phase number is not accurate, or is directly unavailable, then the GPS tracker will not work. In addition, if the height angle of the satellite (the angle between the satellite and the ground level) is too small during the measurement, measurement positioning cannot be performed. In summary, there are no 4 or more satellites in the measurement period, the altitude angle is too small, there are obstructions such as high-rise buildings, the sun is active, the satellite's orbital position and operating conditions, receiver conditions, etc. may cause the GPS tracker to fail. Inaccurate positioning or positioning.

GPS Tracker module

Application of GPS tracker module

1, mobile phone: now Baidu map, Gaode map, WeChat, etc. in the smart phone can use the GPS tracker positioning, because the built-in GPS tracker module.

 

2, car tracker: Now many new cars have built-in GPS tracker module when they leave the factory, you can directly locate. There are also rental locators, car wind control industries, etc., which use car locators to ensure the safety of cars.

 

3, personal tracker: can be directly positioned, there is a one-click SOS help function and so on.


4, pet tracker: also uses the GPS tracker module

 

5, ship ocean navigation and inbound water diversion

 

6, various levels of geodetic, control measurements