Data Preprocessing And Quality Check For GNSS Observation Data

With the development of GNSS,there will be more than 100 satellites in the flowing 10 years, the accuracy of navigation and position will also be improved by muti-GNSS. Carrier phase observations are usually used in high-accuracy position on condition that all cycle slips are correctly detected. GNSS data quality is an indicator of GNSS receiver’s performance, it is also related to the method of data processing. As a result, the research about cycle slip detection for Beidou and data quality check for GNSS is done based on Beidou Analysis and Service Center, Chang’an University. In this paper, four main works related to cycle slip detection and GNSS data quality check have been done as follows:(1)The combination of GNSS observation is investigated and the limiting fator of optical combination is proposed. Then the frequentely-used combination of double-frequency and tri-frequency observations is analysised.(2)The new version of Rinex 3.02 and the commands of TEQC which is often used to analyse GNSS data quality is introduced.The principle of data quality check of TEQC is al-so detailly analysed.(3)Diverse cycle slip detection methods are introduced when single /double/tri-frequency observations are processed. The applicable scope and effect of every method is also analysised. For BDS single frequency data, high order difference and dopper method is used, the results show that both methods are effected by observations’ interval obviously except the geostationary orbit satellites adopted the manner of high order difference.M-W and STPIR methods are usually used when double frequency signals are processed,the result shows that the combination of the two method can greatly improve the correction of the detecteion and recovery of cycle slip. For cycle slip detection of tri-frequency observations, the combination of tri-frequency pseudorange and phase and tri-frequency geometry-free phase combination is also employed. At last, tri-frequency geometry-free and ionosphere-free phase combination is proposed, the result shows that this method can detect all kinds of small cycle slips accurately except one group of insensitive cycle slip.(4)Based on the principle of TEQC’s data qulity check, we develop a software called QC which is similar to TEQC,by which the latest Rinex version of GNSS data can be analysised. The reliability of this software is also verified,then we analysis the data quality of BDS observations. The results show that quartz clock in some GNSS receivers are unstable with the probability for clock jump, the multipath periods for BDS GEO is not obvious compared to GPS, what is more, the SNR of BDS is also different from GPS and GLONASS.