What are the applications of GPS measurement?

The GPS global satellite positioning system is a large-scale space program sponsored by the US Department of Defense in the 20th century. The GPS space constellation is composed of 21 working satellites and 3 standby satellites in orbit, distributed on 6 equally spaced orbital planes. Simultaneously transmit two kinds of signals (C/A code and P code); it has the characteristics of global scope, all-weather, all-time domain, continuous fast and so on. The GPS positioning system measures the carrier phase of satellite signals to achieve precise relative positioning. With continuous improvement and optimization of mathematical processing methods, the accuracy of GPS measurement is greatly improved.

The technical design of the GPS control network is the basis for GPS positioning. It is carried out in accordance with the relevant national regulations (regulations), the use of the GPS network and the requirements of users. Its contents include: project source, survey area overview, engineering overview, technical basis, Measurement plan, operation requirements, observation quality control, data processing plan, etc.; determination of main GPS measurement accuracy indicators and network design.

According to different purposes, there are four basic ways to construct a GPS network:

The dot-connection type is the connection between adjacent synchronization patterns (that is, the closed pattern formed by the baselines obtained by multiple receivers simultaneously observing satellites, also known as synchronization loops) with only one common point connection. The geometric strength of the figure formed by this method is very weak, and it is generally not used alone.

Edge-connected type refers to the connection between adjacent synchronized graphics by a common baseline. In this kind of network layout scheme, the number of re-measured edges is more, and the geometric strength of the network is higher, which is better than the point-connection type.

GPS network connection type refers to the connection of two or more common points between adjacent synchronized graphics; its geometric strength and reliability are higher, and it requires more expenditure and time. Generally, it is only used for high-precision GPS measurement.

Edge-point hybrid connection refers to the organic combination of point-connection and edge-connection to form a GPS network. This method can not only ensure the geometric strength of the network, improve the reliability of the network, but also reduce the workload of the field and reduce the cost, so it is a relatively ideal method of network deployment.

GPS networks have corresponding design guidelines. GPS point selection: It is mainly convenient for signal reception and uninterrupted and convenient for storage.

There are several ways to improve the reliability of the GPS network: (1) Increase the number of observation periods; (2) Ensure a certain number of repeated stations; (3) Ensure that each station is connected to at least three independent baselines; (4) In When laying out the network, the minimum number of asynchronous ring edges in the network should be no more than 6.Because GPS measurement stations do not require visibility between stations, and the graph structure of the network is more flexible, the work of selecting points is simpler than conventional surveying. However, the point should be selected in a place with convenient transportation and easy installation of receiving equipment, and the field of view should be wide; GPS points should avoid objects that interfere with electromagnetic waves, such as high-voltage lines, television stations, microwave stations, and large areas of water. After the points are selected, the markers are embedded as required and the points are drawn.

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