GPS历书数据的有效龄期

历书数据的有效性是决定接收机启动状态进而影响首次定位时间的重要因素之一。对不同龄期的历书数据在估计卫星仰角、信号传播时延、多普勒频率偏移和GDOP值时引入的误差进行测试和分析,提出了截止角递增选星法,将GPS历书数据的有效龄期从一个月延长至一年,为接收机启动时充分利用GPS历书数据,辅助卫星信号的快速捕获提供有力的依据。

Effective Age of GPS Almanac Data

The effective age of GPS almanac is an important factor in the determination of receiver's startup state,which will affect the first positioning time.Errors of satellites' elevation,signals' propagation delay time,doppler frequency drifts and constellation's GDOP calculated by almanacs with different ages are analyzed.By raising a new satellite selection method which is based on the gradually increasing cut-off angle,the effective age of GPS almanac is prolonged from one month to one year.This paper offers a powerful proof that making full use of GPS almanac can realize the fast acquisition of GPS signals when the receiver starts.