低视线垂直折光对EDM三角高程测量的影响

The Influence of Atmospheric Vertical Refraction in the Near Earth Surface upon EDM Trigonometric Levelling

大气垂直折光是影响EDM三角高程测量精度的制约因素之一.本文通过对某市GPS控制网下布设的一、二级导线中384组低视线往返EDM三角高程测量资料的分析,探讨了低视线垂直折光的一般规律及其对EDM三角高程测量的影响;提出了如何用测区平均折光系数进行改正的方法,并将计算结果与水准测量结果进行了比较,得出了一些有实用价值的结论.最后依据计算分析,指出了以0.1S/km作为往返测高差之差限值的局限性,并给出了具体解决方法.

Atmospheric vertical refraction is the main factor which affects the precision of EDM trigonometric levelling. Through statistic analysis of 384 pairs observations of EDM trigonometric lelleving which are gotten from grade 1 and grade 2 traverses laid out under an urban GPS network, the authers have studied the characteristics of vertical refraction in near earth surface and its influence on EDM trigonometric levelling. The authors have also conducted height difference correction approach by using average refraction coefficient of the survey area and compared the corrected results with levelling results and gotten good results. Based on the practical surveying data, the authors have pointed out the limitation of the specifications in using formula 0. 15/km as the tolerance of the differences of height differences and recommended one method to solve it.