The Research Of GPS Single-point Positioning

In this paper the mathematical models and methods for GPS single-point positioning are studied systematically on the theory.All kinds of error correction formulas are studied,such as ironsphere correction,troposphere correction,relativistic effect correction,earth rotation correction ,earth tides correction ,satellites antenna phase center offset correction. GPS single-point positioning programs 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 .The results are computed with the 24 hour pseudoranges observation data before and after the canceling of the SA.The result show that before the canceling of the SA,the single-point positioning error is about 4 metres,after the canceling of the SA ,the error is about 2 metres.The positioning result of phase and broadcast ephemerides are gained using time-satellite differential model after canceling SA, the precision for 24 hours phase observation data is about 1.1 metre,the precision for 2 hours phase observation data is about 1.3 metre,the precision for 1 hour phase observation data is about 1.6 metre ,the precision for 20 minutes phase observation data is about 2.7 metre.The last,the single-point positioning precision for 40 minutes using precise ephemeredes and carrier phase observation data is about 1 metre,the precision for 2 hours is about 0.6 metre. The satellite position and clock offset at any time can be gained through interpolating precise ephemeredes using CHEBYSHEV polynomial coefficients.The results of computation are analyzed and compared,and some beneficial conclusions are gained.