Research On The Technology And Optimization Method Of Multi-constellation And Multi-frequency Network RTK Ambiguity Resolution

With the construction and modernization of Global Navigation Satellite Systems, multi-constellation and multi-frequency network RTK becomes an important direction and significant object gradually. Aiming to the ambiguity resolution in multi-frequency network RTK including BDS triple-frequency observations and the high-dimension ambiguity resolution in multi-constellation network RTK, this paper proposes a new model of multi-frequency network RTK ambiguity resolution and a partial ambiguity fixing strategy which can be suitable for practical engineering application. The technology and optimization method of multi-constellation and multi-frequency network RTK ambiguity resolution are researched thoroughly. The performance is compared and analyzed with traditional method and the technology is applied into CORS software practically based on that. The main contents and results are as follows.1. Mainly taking BDS triple-frequency observations as examples, many common combined observations and their applications are analyzed.2. Based on the analysis of common multi-frequency ambiguity resolution models, the model of network RTK ambiguity resolution proposed by this paper is illustrated in detail. Ratio value, success rate and integer ambiguity bias are compared and analyzed with traditional model by experimental data. The results show that compared with traditional model, the ratio value of multi-frequency model improved by 88.4% on average and the success rate appear much higher and more stable than it of traditional model. Meanwhile, the integer ambiguity bias of multi-frequency model is also better than it of traditional model. Therefore, it can be concluded that the ambiguity resolution of multi-frequency model is more accurate and reliable than traditional model.3. Based on the research of partial ambiguity fixing, the network RTK partial ambiguity fixing strategy and its reason is discussed adequately, the reliability of ambiguity fixing, computing efficiency, and compatibility are analyzed by experimental data. The results show that the new strategy proposed by this paper can improve the ratio value of ambiguity fixing greatly in network RTK and the percentage of its effective use can reach about 50%, which can improve the reliability of ambiguity resolution in network RTK obviously. Meanwhile, its computing efficiency and compatibility can also fulfill the requirements of practical engineering application.4. On the basis of CORS system software EarthNet V3.0, the technological process of multi-constellation and multi-frequency network RTK ambiguity resolution is illustrated particularly. The ratio value and success rate are compared and analyzed with traditional technology by experimental data. The experimental results show that the ratio value in the method proposed by this paper is higher than it in traditional method in most cases and the ratio value of ambiguity resolution of JNNF-LHNF baseline at the length of 41.5 km is improved most significantly and reaches to 91.1%. Meanwhile, the success rate in the method proposed by this paper can reach to 100% at every epoch. Therefore, the method proposed by this paper can efficiently improve the model strength and reliability of network RTK ambiguity resolution in CORS system software.