GPS英文论文翻译.doc

GPS Solut (2009) 13:173–182 DOI 10.1007/s10291-008-0110-3 Kalman-filter-based GPS clock estimation for near real-time positioning Andre′ Hauschild . Oliver Montenbruck Abstract In this article, an algorithm for clock offset estimation of the GPS satellites is presented. The algorithm is based on a Kalman-filter and processes undifferenced code and carrier-phase measurements of a global tracking network. The clock offset and drift of the satellite clocks are estimated along with tracking station clock offsets, troposphericzenith path delay and carrier-phase ambiguities. The article provides a brief overview of already existing nearreal-time and real-time clock products. The filter algorithm and data processing scheme is presented. Finally, theaccuracy of the orbit and clock product is assessed with aprecise orbit determination of the MetOp satellite andcompared to results gained with other real-time products. Keyword Clock estimation Precise orbit determination Real-time Kalman filter Introduction A growing number of near real-time precise point positioning (PPP) applications raise the need for precise GPS orbit and clock products with short latency. One of these applications is the precise orbit determination (POD) of remote-sensing satellites, which is to be performed shortly after a ground station pass. The observations of the satellite’s GPS receiver are available immediately after the download to the ground station. For processing these data,the user requires precise orbit and clock data for thecomplete GPS constellation. The rubidium and cesium atomic standards of the GPS satellites are subject to clock noise and frequency variations, which can originate from a variety of effects and are hard to forecast. Predictions of clock offset and drift, which are provided for example in the predicted part of the ultra-rapid orbits provided by IGS or the broadcast ephemerides, will deviate quickly from the true values by several decimeters or even meters. Thus,th