Abstract: The method of realtime positioning for LEO satellites was studied. GPS positioning is usually used in the realtime positioning of low orbit satellites. Due to the use of broadcast ephemeris parameters and ordinary crystal vibration, the precision is generally within 10m, which cannot meet the needs of highprecision realtime positioning. IGS organization generates the precise ephemeris and clock error products through the global GPS tracking analysis centers, and releases the SSR ephemeris and clock error correction products on the Internet. These IGS products were investigated,and it was put forward that under the condition of existing observing and controlling support, highprecision location of SSR could be achieved by highdensity injection of information flow. The background of augmentation load for a low orbit micro satellite was applied. The ephemeris and clock difference of a dual frequency GPS receiver were corrected with 1057 and 1058 data in IGS03 products, using the recursive least square estimation and LAMDA fuzziness to deal with the carrier phase and pseudo distance information.

Key words: SSR data flow, IGS precise ephemeris, nondifferential precise point positioning, navigation and positioning, low orbit satellites