The Spatio-temporal Visbility Analysis Of Navigation Satellites In 3D Urban Space

The global navigation satellite system(GNSS)has been applied to all aspects of modern social life.GNSS has an unparalleled advantage of other navigation technology,which provides real-time/post-event high accuracy three-dimensional(3D)absolute coordinates information for all ground and air navigation equipment.GNSS has become national spatio-temporal information basis equipment,an irreplaceable function in national productive life and defense construction areas.However,urban canyons result in receiving satellite number dramatical reducing,even introducing multi-path and other errors in some satellites observation value,which has a serious impact on satellites navigation positioning in urban areas and brings many problems.The spatio-temporal visibility analysis method of navigation satellites in urban stereoscopic space(including urban road areas)is proposed to well use GNSS navigation positioning in this dissertation.The main research contents are as follows:(1)The GNSS precise ephemeris satellites positions are calculated by using Sliding Generalized Extended Interpolation Method to solve the inconsistency problems of GNSS different system precise ephemeris calculating satellites position methods.The precise ephemeris of GNSS different orbit types is utilized to analyze the influence of different parameters combination on precise ephemeris interpolation accuracy.The optimal parameters combination of different orbit types is determined to achieve all systems at precise ephemeris calculating satellites position adopting the same method.To the GLONASS broadcast ephemeris low efficiency problem that high accuracy positions are calculated by continuous iteration,satellites positions are calculated by utilizing Sliding Chebyshev Polynomial Fitting Algorithm.By experiment comparison analysis selecting the optimal fitting time interval and order,and the Sliding Chebyshev Polynomial Fitting Algorithm is well applied to calculate satellite position.(2)The method of navigation satellite spatio-temporal visible calculation is proposed,based on road street view imagery,for reducing the dependence of existing methods calculating satellite visibility number on high precision 3D city models in urban road areas.The proposed method uses the street view and different timescales ephemeris data to calculate the satellite visibility number.To evaluate the effectiveness of the proposed method,Wuhan and Shanghai were taken to map the spatio-temporal visibility of satellites in road areas.(3)The satellite visibility calculation of urban stereoscopic space can not be achieved based on road street view imagery.Therefore,this dissertation proposes the calculation method of satellite visibility based on airborne point cloud in 3D urban space.Firstly,for the problem that the existing GNSS visibility calculation does not take into account the influence of trees on signal,the full paths transmission model of satellite signal is established.The realmeasurement data is used to calculate model parameters and evaluate precision.And the navigation satellite visibility simulation method of trees impact is proposed based on the above model.Secondly,the calculation of satellite visibility is developed for building blocks.The simulation results under the influence buildings and trees are integrated to obtain the satellite spatio-temporal visibility in 3D urban space.The experiments demonstrated that the full-paths signal model can accurately calculate the satellite visibility number of GNSS in trees areas in 1 square kilometer test areas.The spatio-temporal visibility fast calculation method of urban full space navigation satellite is proposed,which is high-accurate and wide range.