中文摘要：

当基线两端高差较大时,即使基线较短,其气象条件也有所差异,导致对流层延迟不能通过双差得到有效削弱。为了分析高差对相对定位精度的影响,利用香港连续运行参考站网络数据进行不同策略的计算实验。结果表明：若不利用标准气象模型（推算气象元素）及经验大气延迟改正模型,由高差带来的残余对流层延迟较大,甚至可导致基线解算失败;即使加入对流层延迟改正,起算气象元素的误差也将带来较大的大地高测量误差;增加观测时间可以削弱残余对流层延迟随机部分的影响。

英文摘要：

When the height difference between the ends of the baseline is large, the tropospheric delay can not be mitigated by the usually used double difference technology even if the length of the baseline is short. It is caused by the different weather condition between the ends of the baseline with large height difference. In order to analyze the height difference effect on GPS vertical accuracy, the several computing tests were carried out by using the data from Hong Kong GPS reference network. Some conclusions can be drawn from these test results. The first, the residual tropospheric delay will be big without using empiric tropospheric delay model and standard atmosphere model when the height difference is large. The second, the errors of meteorology observation on sea level will bring about some errors in GPS vertical direction even the empiric tropospheric delay model and standard atmosphere model are used. The third, observations for a long time can smooth some stochastic effects of the residual tropospheric delay.