| With the continuous development and perfection of the global satellite navigation positioning system, satellite positioning technology with high-precision has been widely applied to many areas such as transportation, communications and geomatics. At the same time, the application scope and the cost of measurement are also concerns on the basis of meeting the requirements for positioning precision. The technology of bathymetric survey without tide observation combined RTK with sounding technology has been applied to some extents. But when using this method, there are limitations that it needs at least two receivers and the measuring range is limited by the distance from the base station. The precise point positioning (PPP) technology can achieve high-precision positioning by only using one receiver, so PPP isn’t limited by the distance to the base station. What’s more, combining the mutli-GNSS positioning can make full use of more satellites and enhance the reliability of the positioning. In this paper, on the base of further research of the multi-GNSS Kinematic PPP, it is applied to bathymetric survey without tide observation. The main contents and achievements of the paper are summarized as follows:(1) The function model, the stochastic model and the error processing method of PPP were elaborated in detail. The characteristics of traditional model, UofC model, model without ambiguity and the weight determining methods based on priori model and posteriori estimation were analyzed. The main error sources which affect the accuracy of PPP and the methods of calculating or eliminating these errors were studied.(2) The main data processing methods of Kinematic PPP were further studied. In the pre-processing phase, the Lagrange interpolation, clock jump and cycle-slip detection and millisecond clock jump correction are respectively analyzed. In the filtering calculating phase, the theory of robust Kalman filtering with water level constraints was elaborated. Compared with the standard Kalman filtering in examples, the influence of gross error is effectively weakened and the positioning stability is improved by using robust Kalman filtering.(3) The results of Kinematic PPP were analyzed respectively based on GPS, GLONASS, BDS and combination of them. The positioning precision and convergence speed of the results with single system and multi-GNSS are compared by using observation data from Tianjin CORS. The results show that the number of available satellites can be effectively increased by multi-GNSS positioning. Because of the multi-GNSS positioning can provide enough redundant observations for positioning, the stability and reliability will be improved. According to the statistical results, it needs 22.38 minutes on average when errors converge to 10 cm based on multi-GNSS Kinematic PPP. The result is accelerated by 84.8% compared with the results of GPS. The RMS of positioning error in N, E and U directions respectively is 1.46 cm,3.21 cm,2.49 cm after convergence, and the positional accuracy is increased by 12.9% compared with the results of GPS.(4) The multi-GNSS Kinematic PPP was applied to bathymetric survey without tide observation. The basic principle of bathymetric survey without tide observation and the transformation approach between different heights are stated. The measurement process of bathymetric survey without tide observation, the instrument specifications and the data processing method in the office are described. Experimental results show that, there is 4 cm difference between the elevation calculated by PPP and RTK on average. Compared the airbase water level calculated by PPP results and the sounding data to the data provided by tide station, the water level of 99.7% measuring points exist deviation within 20 cm. The accuracy can satisfy the precision requirement of the water depth measurement. |
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