Application Research Of Method Of Large GNSS Network Realtime Data Rapid Solution

With more and more importance of GNSS in different fields, many countries have built GNSS networks comprised of thousands of reference stations. One example is CMONOC of 260 stations, main purpose of which is to monitor China mainland plate motion for recovering co-seismic motion. Such GNSS networks, especially these large networks produce new challenges. Real-time estimation required by monitoring co-seismic motion is still a difficult issue. Considering the frequent earthquakes have caused large life and property loss and bad effects on world economy, it is meaningful to monitor earthquake and extract geophysical signals by such large networks such as CMONOC, while promoting the development, method and technique of real-time estimation. And it is also a hot topic in GNSS research field all over the world.This paper deeply discusses and researches important issues in GNSS real-time data processing, including the GNSS real-time quality controlling, real-time satellite clock error estimation, GNSS large network ambiguity fixing based on single-station kinematics mode, modified sidereal filtering etc. The main contents and related conclusions including:1. This paper researches method and technique of GNSS large network real-time data processing. As time needed by GNSS solution is about 0(n3), which could not satisfy the requirement of real-time processing, this paper studied several related key techniques:This paper studied real-time quality control method. 1) By analyzing the characteristics of the combination of LG and MW and the sensitivity of cycle slipping, We remove gross error and cycle slips with a posteriori residuals to enhance the reliability of real-time quality control.2) We study cycle slips reparation method and propose a new method to search the best correction from all the possible cycle slips under the principle of minimum a posteriori standard error.This paper studies real-time satellite clock error estimation method and technique. 1) As real-time satellite clock error estimation needs a lot of time, we resolve ambiguity based on epoch-difference method to improve processing speed.2) We determine satellite clock error precise initial value based on no-difference mode to eliminate the system errors of real-time satellite clock error; use quasi-stable datum and extrapolated satellite clock error in order to resolve the instability of reference clock and time delay. 3) We analyze the real-time characteristic of satellite clock error by the concept of time-consuming rate, and study satellite clock error precision and the effects of extrapolated satellite clock error on kinematics positioning by two-difference method.This paper studies kinematics precise point positioning method and technique. We studies major error sources of precise point positioning and propose corresponding processing method. Then we discussed the basic method of parameter estimation with square root information filtering. Finally we use 20Hz, Is,30s GPS data and co-seismic data to test and analyze the method, which is demonstrated to be correct by the results.Considering residuals from error related with receivers'geometry, and continuous observations of CMONOC stations, we use (filtered) sidereal filtering to smooth time series to weaken multi-path effects and improve positioning precision.2. This paper improves quick estimation method and technique. 1) We deeply study network solution for ambiguity fixing based on single-station kinematics mode to improve positioning precision. The details are as the following:obtaining the double difference ambiguity, choosing independent baseline, fixing the double-difference ambiguity of wide-lane and narrow-lane, and network adjustment constrained by ambiguity-fixed estimation with double-difference LC combination. 2) Considering that network adjustment is time-consuming, approaching O(n3), this paper demonstrates it is feasible to reduce the network adjustment processing time to O(n) based on fixed point theory. 3) Tests show single station kinematics positioning precision could be improved, especially in the east direction, usually up to about 10%-40%. And the processing time is actually O(n) with network solution method based on fixed point theory, for example 100 stations using network solution method is only 4% of usual method. When using the method propose by this paper, static positioning for 100 IGS stations with fixed ambiguity on CPU2.8GHz only need 245.3s, about 1% of that of GAMIT time 6hour32min.3.This paper studies modified algorithm for GNSS large network processing. 1) According to the characteristics of GNSS data of CMONOC stations, we propose adaptive constraints for quick ambiguity convergence of precision point positioning. 2) As kinematics constraints are usually used for kinematics positioning, we propose a priori coordinate constraint method. Comparison using real observations shows that these two methods are well-matched but a priori coordinate constraint method could improve precision in certain degree. 3) Considering large biases of satellite clock error when regional stations used for real-time satellite clock error estimation are affected by earthquake, this paper removes or eliminates system error of kinematics positioning by Helmert transformation.4.This paper designs and realizes GNSS precise single epoch network solution (PSENS) software and employs it to actual project. 1) Based on the theory, method and technique in this paper, we design and realize PSENS software, and introduce the overall frame, data processing flow, interfaces and features of the software; 2) We employ PSENS software to Guangzhou CORS system and CMONOC to test the practicability and reliability. By these two projects, we analyze different troposphere mapping function and test the effects of time series smoothing, ocean loading correction, solid earth correction.