Basic principles and applications of GPS measurement

According to the principle of GPS positioning, its positioning methods mainly include pseudorange positioning, carrier phase positioning measurement, and differential GPS positioning. For the pending point, it can be divided into static positioning and dynamic positioning according to its motion state. The so-called static positioning refers to placing the GPS receiver on a fixed point to be fixed and performing observations for several minutes or longer to determine the three-dimensional coordinates of the changed point, so it is also called absolute positioning. If two or more receivers are placed on different side stations, the relative position (coordinate difference) between the receiver antennas on these pending points can be determined through observation for a certain period of time, so it is also called relative positioning.

Based on the principle of distance rendezvous positioning, in a two-dimensional plane, two side lengths are needed to determine another point, while in three-dimensional space, three side lengths are required to determine the third point; the principle of GPS positioning is also based on distance rendezvous positioning principles Bit. Three or more ground points (control stations) fixed on the surface of the earth can be used to intersect to determine the position of satellites in the sky. On the contrary, the known spatial positions of three or more satellites can be used to intersect unknown points on the ground (receiver antenna Center).

According to the status of the GPS receiver during positioning, GPS positioning can be divided into static positioning and dynamic positioning. The so-called static positioning means that the receiver is placed on the measuring station for several minutes to 1h or longer for observation to determine the three-dimensional coordinates (absolute positioning) of a point in the WGS-84 coordinate system, or two The relative position between the points (relative positioning). For dynamic measurement, at least one receiver is in motion, which is consistent with the principle of GPS positioning. What is measured is the point position (absolute positioning or relative positioning) in motion corresponding to each observation epoch.

The principle of GPS positioning can be used not only for static positioning, but also for dynamic positioning. Like static positioning, dynamic positioning can also be divided into absolute positioning and relative positioning. The characteristic of dynamic positioning is that the platform supporting the GPS receiver is a moving carrier. In order to determine the instantaneous position of the moving carrier in the WGS-84 coordinate system, the pseudorange of the ranging code can be used for absolute positioning of a single point. Only a navigation-type GPS receiver is required to complete the dynamic absolute positioning in real time. In the United States After the implementation of the SA policy, the accuracy of absolute positioning is less than 100m, and it can only be used for navigation with low accuracy requirements.

Tags: the principle of GPS positioning; static positioning; dynamic positioning;