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Research On Theory And Method Of Obtaining Kinematic PWV By GNSS

Posted on:2015-09-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:S G XuFull Text:PDF
GTID:1220330461974289Subject:Geodesy and Survey Engineering
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Currently the GNSS water vapor inversion research focuses on static sessional troposphere estimate using static data, then the PWV was applied to the analysis of meteorology such as rainfall after converting the troposphere to PWV. Because the weather always keeps changing, so static sessional estimation could not satisfy real time PWV monitoring. This dissertation mainly aims to improve kinematic troposphere estimation with deep study. The study content of this dissertation can be divided several parts as follow.Firstly the method of improving near real time kinematic PWV obtaining by difference GPS was studied. Real time ZTD can be obtained by only predicted orbitsduring solution in difference GPS, then wet ZTD is converted to real time PWV. In order to improve the solution precision we gave highly precise coordinates to base sation and rover station(static indeed), and the coordinates were tightly constrained with bias no more than 1 cm. After 17 PBO sations were computed it showed that:if the height difference between base and rover is small, then real time PWV can be obtained with 2 mm precision which can satisfy the need of weather forecast; vise versa, this is caused by the high relation between height difference and troposphere difference.The precision of ZTD obtained by two improved PPP contrary to traditional PPP was analyzed. For the reason that the precision of ZTD obtained by difference GNSS is limited by station height difference, PPP’s appearance can cope with this problem, and get rid of the burden of muiltiple receiver’s simultaneous observation in difference GPS. The ambiguities for traditional PPP are flaot because of non-difference between observations, so we tried to fix the ambiguities to integer. Research results showed this can lead to ZTD’s variation with 1-2 mm, and this method can reduce the solution’s convergence time; Besides, we tried to solute ZTD using GPS and GLONASS combination observations, and the research results showed the difference between ZTDs soluted by double constellation and single constellation can reach several cm sometimes, so multiple sonstelltations can obviously improve the reliability of ZTD solution when the observation condition is poor.Basic theory model of ZTD estimate considering various inner and outside error sources’ effect based on the traditional PPP was purposed. The high-order ionosphere error, receiver clock and satellite clock’s effect on ZTD was analyzed, the results showed that 2n ionosphere effect on ZTD can reach 2 mm in low latitude area during ionosphere’s non-active time, but the 3rd ionosphere effect on ZTD is no more than 0.5 mm at the same condition; Clock jump on single observation can lead to ZTD jump of cm level sometimes. According to this phenomenon a clock jump detection methoed was given for high precise real time ZTD solution; The difference between real time satellite clock and final satellite clock can reach several hundred meters, so we need to set up a reasonable process noise for receiver clock.For the first time the precisions of water vapor obtaining by moving GNSS on ocean, land and airborn platform were analyzed using kinematic PPP technique. Reserch results showed ZTD with sigma of about 1 cm can be achieved by GNSS data with shipborn, carborn and airborn, and the PWV’s precision derived from this ZTD is about 2-3 mm.The algorithm of PPP with constrained condition was purposed. The precision of kinematic PPP in traditional mode is about several decimeters, in order to improve the precision of kinematic PPP, some known informations in the practice can be used, the informations include relations between inner parameters and known data outside. The algorithm of PPP with constrained condition was purposed in this dissertation based on these known informations. The experimental data analysis showed the proposed algorithm can largely reduce the parameters’ convergence time, and can improve the positioning precision by PPP, so does the ZTD solution.At last real time kinematic PWV obtained by PPP technique was studied, and the feasibihty of using GNSS to send warming for rainstorm was analyzed. After computing and analyzing the ZTDs of 12 CORS stations in HK area with predicted orbit and real time satellite clock during last of March 2014, results showed the warming measured by GPS is highly consistent with the warming sent by HKO.
Keywords/Search Tags:Zenith Total Delay, Precipitable Water Vapor, Kinematic, Precise Point Positioning, Improved Precise Point Positioning, Real Time, Constrain, Error, Prediction
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