GPT3模型对大高差中长距离RTK的影响分析

Influence analysis of GPT3 model on medium and long-distance RTK with large height difference

对流层延迟是大高差环境下实时动态定位(RTK)的主要误差源,严重影响了RTK的定位精度。为有效抑制大高差环境下对流层延迟对RTK定位的不利影响,提出提升RTK定位性能的合理方案。本文以香港连续运行卫星定位服务综合系统(CORS)站为例,评估了第三代全球气压气温模型(GPT3)在不同季节不同高差基线的对流层模型精度,并在此基础上对比分析了引入GPT3模型约束前后的中长距离RTK的定位性能。结果表明:香港地区19~34 km中长基线相对对流层总延迟的量级在厘米级到分米级,严重影响RTK定位结果。GPT3模型在香港地区的误差在±1 cm之间,可以作为先验对流层信息进行约束。加入GPT3模型的约束后,四条基线的BDS和BDS/GPS组合的RTK定位U分量的精度均有显著提升,BDS提升了35.1%、32.7%、32.3%和56.9%,BDS/GPS提升了29.1%、26.1%、31.2%和63.3%;四条基线的单BDS模糊度固定率分别提升了5.7%、2.6%、6.4%和4.5%,而BDS/GPS组合基本没有影响。此外,先验方差的取值对大高差基线有一定影响,在对流层活跃的月份须根据统计的大气建模误差及时更新先验方差。

Tropospheric delay is the main error source of real-time kinematic(RTK)in large elevation environment,which seriously affects the positioning accuracy of RTK.In order to suppress the influence of tropospheric delay on RTK positioning in the environment of large elevation difference,it is necessary to analyze the influence of tropospheric model and different prior variance on RTK positioning results,so as to propose a reasonable scheme to improve RTK positioning performance.Taking Hong Kong continuous operational reference system(CORS)as an example,this paper evaluated the accuracy of the tropospheric model of the global pressure and temperature model 3(GPT3)with four different elevation baselines in different seasons,and compared and analyzed the positioning performance of the medium and long-range RTK before and after the introduction of the GPT3 model constraints.The results showed that the total relative tropospheric delay of the 19~34 km medium-long baseline in Hong Kong was in the centimeter to decimeter range,which seriously affected the RTK positioning results.The error of the GPT3 model in Hong Kong was between±1cm,which could be constrained as a priori tropospheric information.After adding the constraints of the GPT3 model,the accuracy of the RTK positioning U component of the BDS and BDS/GPS combinations of the four baselines was significantly improved,with BDS increasing by 35.1%,32.7%,32.3%and 56.9%,BDS/GPS increasing by 29.1%,26.1%,31.2%and 63.3%,respectively,and the fixed rate of single BDS ambiguity of the four baselines increasing by 5.7%,2.6%,6.4%and 4.5%,respectively,while the BDS/GPS combination had little effect.In addition,the value of the prior variance had a certain influence on the baseline of the large elevation difference,and the prior variance should be updated in time according to the statistical atmospheric modeling error in the tropospheric active months.