Search

To solve the problem that traditional underwater control point absolute positioning is time-consuming and laborious with low vertical precision, itis put forward that an accurate method with constraints of depth while taking waves into account to get absolute coordinate of underwater control point. Firstly, studiesarecarried outon the wave impact.And methods are put forward to determine the elevation difference between underwater points and the absolute elevation with GPS vertical values and the elevation difference. On this basis, methods are put forward, such asthe circle navigationwith depth's constraint to get single point's absolute coordinate, 2D free net adjustment with depth's constraint, integrated constraint adjustment,with accurate elevation difference, and 3D combined adjustment with accurate elevation difference. Finally, the experimental results show that the proposed methods can double the efficiency of traditional methods and improveprecision by one order of magnitude.

The technique of precise point positioning (PPP) is gradually becoming a popular method in GPS data-processing. In GPS observation equation, the unknown parameters can be separated into two parts: global parameters and local parameters. The global parameters include orbit, satellite clock and geodynamic parameters. The local parameters are site-occupation-spectific, such as position, tropospheric delay, etc. The formulas of local parameters are firstly derived under the network-solution and the PPP-solution conditions respectively. If the weight matrix of global parameters in PPP-solution is small enough, the cofactor matrices of local parameters are the same as that in network-solution. Then, 16 daily solutions are obtained in both PPP mode and network mode. Three sites are selected to compare the solutions. The experimental results demonstrated that the difference between two solutions in coordinates and tropospheric delays are only few millimeters. This level of difference can be neglected so that the ...