Study On The Development Of GPS Precise Positioning & Orbit Determination Software

High-precision GPS data processing software is the prerequisite condition for GPS precise applications. Nowadays, the software we used in GPS precise applications always comes from foreign countries. Relying on the imported softwares will impede us from making outstanding and creative achivements, and will make against the development of our country's satellite plans. In a word, we should comprehensively research the theory of GPS precise positioning and orbit determination and consequently design and develop the GPS precise positioning and orbit determination softwares with Chinese features as soon as possible. Such research and software development will be beneficial to the extension of GPS precise applications in our country, and has significant referrence values for the research of COMPASS precise positioning and orbit determination.The concerned items and achievements of this dissertation are as follows.1. Research on GPS orbit models:The GPS orbit models are comprehensively investigated. Based on the orbit contrast results, proposed that the attraction of other planets, the pole tide and the acceleration from general relativity can be ignored in GPS positioning applications, whereas, in long-arc precise orbit determination applications, these perturbing terms should be considered.2. Research on GPS observation models:The influencing factors in GPS observations are investigated. The methods to remove or reduce the errors are detailed. The data pre-processing algorithms(zero-difference, single-difference, double-difference and triple-difference) are proposed. Furthermore, an optimized GPS independent baseline selection algorithm is given, which is based on 3D spheric Delauney triangulation theory and union-find sets theory, as well considering the GPS single-difference processing results. This algorithm has no the traditional 2D planar algorithm's disadvantages resulting from the map projection process of the regional/globe GPS network onto a plane surface, In addition,the new algorithm's time complexity is O(n*logn), whereas the time complexity of traditional minimum spanning tree (MST) algorithm is O(n2*logn).3. Research on GPS precise positioning and precise orbit determination models: GPS precise positioning models and precise orbit determination models are comprehensively investigated, including the partial derivatives of the parameters with respect to the obsevations, the apriori constraints and the apriori datums, the zero-difference and double-difference positioning, the precise orbit determination based on least square adjustment methods or filter methods and so on. Emphasizing particularly on the precise orbit determination algorithm which is based on least square method using double-difference baseline networks, and the orbit synthesis algorithm which is based on the combination of normal equation systems.4. Research on design and development of GPS software:Proposed a delamination architecture for developing a visual GPS precise positioning and precise orbit determination software. Using Microsoft Visual C++ 6.0 and Compaq Visual Fortran 6.5 as programming languages, design and develope a visual GPS precise positioning and precise orbit determination software, named as JDGPS, which is user-friendly, convenient to manipulate, easy to learn and use, multifunctional, and suitable for the users from general companies. The systemic tests and contrast experiments show that JDGPS is reliable and high-precision.5. GPS precise positioning and precise orbit determination using JDGPS: Regarding IGS coordinates and IGS precise orbits as true values, several experiment of GPS precise positioning and precise orbit determination using JDGPS are detailed and contrasted. The positioning experiment shows that the unweighted rms of 33 IGS station's coordinates components estimated by JDGPS is:North component 3mm, East component 4mm, Up component 4mm; The precision of weekly mean coordinates is:North component 7.6mm, East component 7.7mm, Up component 17.3mm; The orbit determination experiment shows that the orbit synthesizing technic can improve orbit precision evidently, Just using 33 IGS stations, the precision of GPS orbit can attain cm-level (radial component 2.9cm, along component 5.5cm, cross component 5.3cm); The precision of precise positioning and precise orbit determination results from JDGPS is as same as that of IGS results.6. Research on GPS precise time transfer methods:The GPS precise time transfer methods are discussed. The zero-difference precise point postioning algorithm is proposed, The algorithm of GPS carrier phase time transfer method (named as conventional GPS CP) and continuous GPS carrier phase time transfer method (named as continuous GPS CP) are detailed. The experiments of GPS carrier phase time transfer using JDGPS are proposed. The contrast experiment of conventional GPS CP and continuous GPS CP shows that the conventional GPS CP has visible day boundary jumps and continuous GPS CP has a linear trend bias. In addition, we find out more characteristics of NTSC's Ashtech Z12T receiver and NTSCGPS-2 receiver.