Precision Absolute Positioning, And Software Development

The mathematical models and methods for precise absolute positioning are discussed in this paper. The satellite position and clock offset at any time can be gained through interpolating precise ephemerides using CHEBYSHEF polynomial coefficients. All kinds of error correction formulas are discussed, such as the earth tides correction, antenna phase center offset and relativistic effects. Scaling factor of the tropospheric zenith delay orientation is added in the observation equation. The absolute positioning software is coded with pseudoranges and broadcast ephemerides, phases and broadcast ephemerides, and phases and precise ephemerides. And a great amount of computation has been done. Using the data collected at fiducial stations for the Crustal Movement Observation Network of China. First, the point positioning is carried out with the 24 hour pseudoranges observation data before and after the canceling of the SA are computed by broadcast ephemerides, and the results are analyzed. The results show that before the canceling of the SA, the point positioning error is about 5 meter, after the canceling of the SA, the error is about 2 meter. Secondly, the point positioning is done with the 2 hours , 1 hour and 20 minutes phase observation data after the canceling of the SA by using broadcast ephemerides, the precision for 2 hours data is about 1.2 meter, the precision for 1 hours data is about 1.8 meter, better than that for 20 minutes data. Lastly, the phase data of 2 hours on the 125th day in 2000 is used to compute the position with precise ephemerides. In this case, the precision of the point positioning is better than 0. 5 meter.