The GPS system consists of 24 satellites, and at any point on the earth, it can receive signals from at least 4 and up to 9 satellites.
For navigation positioning, the GPS satellite is a dynamic known point. The position of the star is calculated from the ephemeris transmitted by the satellite, a parameter describing the motion of the satellite and its orbit. The ephemeris broadcasted by each GPS satellite is provided by the ground monitoring system. Whether the various equipment on the satellite is working properly and whether the satellite is always operating along a predetermined orbit is monitored and controlled by the ground equipment. Another important role of the ground monitoring system is to keep each satellite at the same time standard – GPS time system. This requires the ground station to monitor the time of each satellite and find the clock difference. It is then sent to the satellite by the ground injection station, which is then sent to the user equipment by the navigation message. The ground monitoring system of the GPS working satellite includes a master station, three injection stations and five monitoring stations.
The task of the GPS signal receiver is to capture the signals of the satellites to be tested selected according to a certain satellite height cut-off angle, and track the operation of these satellites, and transform, amplify and process the received GPS signals to measure The propagation time of the GPS signal from the satellite to the receiver antenna, the navigation message sent by the GPS satellite is interpreted, and the three-dimensional position, position, and even three-dimensional speed and time of the station are calculated in real time.
The navigation and positioning signal transmitted by the GPS satellite is an information resource that can be shared by countless users. For users of land, sea and space, as long as the user has a receiving device capable of receiving, tracking, transforming and measuring GPS signals, ie a GPS signal receiver. GPS positioning signals can be used for navigation and positioning measurements at any time. Depending on the purpose of use, the GPS signal receivers required by the user also vary. At present, there are dozens of factories in the world that produce GPS receivers, and there are hundreds of products. These products can be classified according to principles, uses, functions, and the like.
In static positioning, the Fleet Management 3g Gps Tracker Support Take Pictures receiver is fixed in the process of capturing and tracking GPS satellites. The receiver measures the propagation time of the GPS signal with high precision, and uses the known position of the GPS satellite in orbit to solve the position of the receiver antenna. Three-dimensional coordinates. Dynamic positioning is the use of a GPS receiver to determine the trajectory of a moving object. The moving object on which the GPS signal receiver is located is called a carrier (such as a ship in navigation, an airplane in the air, a traveling vehicle, etc.). The GPS receiver antenna on the carrier moves relative to the earth during the tracking of the GPS satellite, and the receiver uses the GPS signal to measure the state parameters (instantaneous three-dimensional position and three-dimensional velocity) of the motion carrier in real time.
The receiver hardware and in-flight software as well as post-processing software packages for GPS data form a complete GPS user equipment. The structure of the GPS receiver is divided into two parts: an antenna unit and a receiving unit. For geodetic receivers, the two units are generally divided into two separate components. The antenna unit is placed on the station during observation. The receiving unit is placed in the appropriate place near the station, and the two are connected by cable. A whole machine. Some antenna units and receiving units are also made into a whole, and they are placed on the test site during observation.