The Creation Of CGCS2000 Plate Motion Models

The technology of global satellites navigation and positioning and earth observation has been rapidly developing, which will help people more deeply understand earth, so it's urgent to define the Terrestrial Reference System according to the best discipline of the earth's motion and establish Terrestrial Reference Frame to provide service.From 1990s, modern aerospace technology mainly included the global navigation satellite system (GNSS) has been developing rapidly, and the observation technology mainly observed the earth's surface has also a fundamental change,so it's urgent to need a high-precision, geocentric, dynamic, uniform coordinate system as a reference system for position measurement. In the meantime, International GNSS Service (IGS) provides international terrestrial reference frame (ITRF). IGS belongs to International Association of Geodesy (IAG) and does a great amount of work for the establishment of national reference frame and local reference frame. In order to fit the trend of development of geocentric coordinate system, our country start formally using geocentric coordinate system---China Geodetic Coordinate System(CGCS2000).This paper initially attempts to discuss how to establish and maintain our country's terrestrial reference frame, and applies 28 national-level CORS stations to establish plate motion models based onCGCS2000.Main contribution and research results are as follows:(1)systematically introduce the academic contents of consultative geocentric reference frame.Reference frame is a substantially coordinate system. This paper systematically introduces the contents about ITRS/ITRF, especially new terrestrial reference frame ITRF2008, CGCS2000 and their relation between them, especially the rigid transformation between ITRF and CGCS2000.(2)In order to realize unifying principle of terrestrial reference frame, this paper puts forward a new method of data in local area network brought into ITRF.Based on the partial derivatives relationship of coordinates and velocities at different epoch along with 7 transform parameters and their rates between two reference frames, variance-covariance matrices of station coordinates and velocities in an old frame can be transformed into a new frame by a rigorous transformation method. On the basis of it, this paper ignores the influence of velocities and 7 transform parameters rates and simples the above process to realize the variance-covariance matrices of station coordinates between two reference frames at the same epoch. By the method, local area data can be brought into ITRF and avoid data processing repeat simultaneity. Moreover it's convenient to use directly international data products existed in the Internet. Analyzing the results of the example, discover that the transformed coordinates deviation can excel 0.1mm level, which can meet the transformation request between two reference frames. This paper can be used for reference to unite data in different reference frames.(3)Introduce the basic principle of plate motion models, and summarize the research about plate motion in the area of China at home and abroad. Based on that, the area of China and circumjacent is repartitioned again.There are two basic hypothesizes of plate tectonics motion:①Plate has the rigidly physical property, and there is no clearly plastic deformation in the inside of plate.②The theory of plate tectonics motion claims that superficial area of earth(or radius of earth) has no clear increase or reduction. Based on those hypothesizes, Euler law can be lead in to describe plate motion. Research methods of plate motion can be divided into two categories, namely, geology and geophysics method and space geodesy method. Using the two methods, researchers at home and abroad establish many motion models, for instance, at abroad there are many world models such as NUVEL1A,PB20,APKIM2005,while our country's researchers established ITRF97VEL,ITRF2000VEL and so on.In the process of plate motion models establishment, the determine of plate boundary is in relation to the precision of final models, so based on the research at home and abroad, the area of China and circumjacent is repartitioned again in this paper, totally 7 plate blocks(4) The method study of reference frame stationsThe stations constrained on international terrestrial reference frame (ITRF) with modern space geodetic techniques are chosen with some random and uncertainties, which directly affects the precision and reliability of ITRF. This paper summarizes a system method to select stations on the rigid plate. Namely, firstly, analyse the quality of data at each station. The second step is rigorous selection to use 7 parameters transformation. The third step is supervision clustering to eliminate some stations that is largely affected by local diastrophism. Finally, make stations well-proportioned spacial distribute. By the method, IGS frame station can be chosen in GNSS data processing to establish high precision terrestrial reference frame.(5) The creation of CGCS2000 plate motion models and result analysisIn order to maintain CGCS2000, main factors to consider is plate tectonics motion, this paper use horizontal direction data of 28 national-level CORS to establish CGCS2000 plate motion models, which reaches cm-level accuracy and has more high accuracy than other models such as ITRF, NUVEL1A,PB2002,APKIM2005 and other research production at home.