Theory And Experiments On Beidou Reference Frame Estabilshment

China's BeiDou Global Navigation Satellite System is accelerating its construction.It not only serves national defense construction,economic development and researches in earth science and other fields,but is also closely related to our daily life.A uniform and high-precision geodetic datum is essential for BDS products and its services.Currently,BDS uses China Geodetic Coordinate System 2000(CGCS2000),which cannot meet its growing demands.Thus,it is urgent to establish a global reference frame especially for BDS(It is called "Beidou Terrestrial Reference Frame" in this paper).Researches on theory and experiments of Beidou Terrestrial Reference Frame establishment were carried out,and the main achievements and conclusions are summarized as follows:1.The definition of an ideal terrestrial reference system and the basic method of realizing an terrestrial reference frame were described.Datum definition of TRF were dicussed in detail.The realization and improvements of the latest ITRF2014 is introduced.2.TRFs in satellite navigation and positioning are summarized.Then the definition and realization of TRFs currently used by the four global satellite navigation systems,that is,World Geodetic System 1984(WGS 84)?Parametry Zemli 1990(PZ-90),Galileo Terrestrial Reference Frame(GTRF)and CGCS2000,are introduced in detail,based on which the characteristics of GNSS reference frame are summarized,and the method of establishing a custom-made TRF for GNSS is discussed,which provides reference for the establishment of Beidou Terrestrial Reference Frame.3.The necessity of establishing Beidou Terrestrial Reference Frame is discussed.Beidou Terrestrial Reference Frame should adopt the definition of International Terrestrial Reference System(ITRS),and be consistent with the latest ITRF.The necessity of building BDS ground control stations overseas is demonstrated and 11 overseas stations are suggested to be built by analyzing their coverage for Beidou satellites.The CMONOC(Crustal Movement Obeservation Network of China)stations and IGS stations are selected to simulate BDS ground control stations which have already been built or are going to be built,and their obeservations are used to realize Beidou Terrestrial Reference Frame,during which different experimental schemes are adopted to research on data process details,and the experimental results are as follows: 34 globally distributed IGS core stations are selected to provide ITRF datum;the adoption of global H-file in the network adjustment may reduce the calculation precision;the best experimental results of this paper are the coordinates and velocities of the 16 simulative BDS ground control stations at J2014.0 calculated by observations spanning five years(every November from 2011 to 2015),which is adopted as the realization of Beidou Terrestrial Reference Frame and the E,N,U component errors of their coordinates and velocities are 0.30 cm,0.26 cm,1.12 cm and 0.27 cm/a,0.22 cm/a and 0.49 cm/a respectively.4.The transformation parameters between ITRF2008 and Beidou Terrestrial Reference Frame are calculated,and based on which the origin,scale and orientation differences between them are analyzed.The transformation from Beidou Terrestrial Reference Frame to CGCS2000 are realized by two methods:(1)using the relationship of the two reference frame with ITRF2008 and ITRF97,and the transformation parameters of different ITRF realizations provided by IERS;(2)calculating the transformation parameters between the two reference frames by two sets of coordinates of their commons points.The results of this two methods are compared and the second method is recommended.The transformation parameters between Beidou Terrestrial Reference Frame and WGS 84 are calculated using the second method,and the transformation between Beidou Terrestrial Reference Frame and PZ-90 as well as GTRF are discussed.