Zhou Xuhua

Estimation of the inter-frequency clock bias for the satellites of PRN25 and PRN01

We present two efficient approaches, namely the epoch-differenced (ED) and satellite- and epoch-differenced (SDED) approaches, for the estimation of IFCBs of the two Block IIF satellites. For the analysis, data from 18 stations from the IGS network spanning 96 d is processed. Results show that the IFCBs of PRN25 and PRN01 exhibit periodical signal of one orbit revolution with a magnitude up to 18 cm. The periodical variation of the IFCBs is modeled by a sinusoidal function of the included angle between the sun, earth and the satellite. The presented model enables a consistent use of L1/L2 clock products in L1/L5-based positioning. The algorithm is incorporated into the MGPSS software at SHAO (Shanghai Astronomical Observatory, Chinese Academy of Sciences) and is used to monitor the IFCB variation in near real-time.

Effect of ocean tides on the determination of zenith delay

Abstract GPS meteorology is a new field in GPS applications, in which precise determination of zenith delay is a key component. A strong correlation exists between the vertical displacement caused by ocean tide and the zenith delay at a given GPS station, so the effect of ocean tide on the precise determination of the zenith delay can not be neglected. We have processed and analyzed the GPS data of the Crustal Motion Observation Network of China from Day 10 to Day 40 of 2001, and the result shows that such effect varies over a range of several millimeters. For example, it is ± 7mm for the coastal station at Shanghai and ±1 mm for the inland station at Wuhan at maximum.

Earth gravity field recovered from CHAMP science orbit and accelerometer data

The earth gravity field model CDS01S of degree and order 36 has been recovered from the post processed Science Orbits and on-board accelerometer data of GFZs CHAMP satellite. The model resolves the geoid with an accuracy of better than 4 cm at a resolution of 700 km half-wavelength. By using the degree difference variances of geopotential coefficients to compare the model CDS01S with EIGEN3P, EIGEN1S and EGM96, the result indicates that the coefficients of CDS01S are most close to those of EIGEN3P. The result of the comparison between the accuracies of geopotential coefficients in the above models, indicates that the accuracy of coefficients in CDS01S is higher than that in EGM96. The geoid undulations of CDS01S and GGM01C up to 30 degrees are calculated and the standard deviation is 4. 7 cm between them.