Precise GPS orbit determination for the earth crustal movement study in the southwestern Pacific region.

摘要

A centimeter-level precise static relative positioning solution using the Global Positioning System (GPS) in the Southwestern Pacific region is presented. The key factor leading to this high precision solution is the simultaneous determination of GPS satellite orbits with high precision.;To validate the methods and results in this study for using GPS to monitor the regional crustal deformation in the Southwestern Pacific region, a criterion is set up to assess the precision of different solutions. Efforts in various aspects are made to fully exploit the information in the GPS phase observation and improve the precision of the solutions. The GPS positioning geometry is analyzed in detail so that the best determined geometric quantities can be picked up for the crustal deformation study. An orbit dynamics model has been developed to model the small perturbing forces on the GPS satellites caused by the solar panel mispointing. Algorithms have been developed to evaluate the effect of different error sources on the positioning solutions.;Experiments are made for each campaign of the Southwest Pacific GPS Project (SWP) to find the best combination of proper force model selection and data segmentation. The precision of each solution is evaluated based on the short term repeatability of the baseline components. From the baseline length changes over the four years (1988-1992) of the SWP period, some characteristics of the crustal deformation in the region are detected and presented.;With the support of the tracking data from the initial International GPS Service for Geodynamics (IGS) campaign, RMS of baseline repeatability at the level of 1-2 parts per billion has been obtained for baseline length solutions of up to 4000 kilometers. With such precision, the relative plate motion across the Tonga Trench during a one-month period can be detected.