根据气温变化率进行三角高程测量的折光改正

不同的气温梯度会产生不同的大气折射，根据测程前后两半段的气温梯度与－0.0342之差值，可将光线沿测程方向的折射分为4种类型，它们对三角高程测量的往返高差均值会产生不同的影响.利用测程两端及

Atmospheric Vertical Refraction Correction for Triangular Altitude Survey according to Atmospheric Temperature Change Rate

Different atmospheric temperature gradients can bring about different atmospheric vertical refraction. The light refraction along the surveying distance can be divided into four types on the basis of different atmospheric temperature gradients on two half surveying distance minus -0.0342. The four types have different influence on average forward and backward triangular altitude difference. This paper presents a method about atmospheric vertical refraction correction for triangular altitude survey according to atmospheric temperature change rate between two end points and three points from 1/4S, 1/2S, 3/4S ,and simulates curves of the second degree of atmospheric temperature gradients along two half surveying distance by mathematics. The method is applied to all the four types of atmosphere vertical refraction. The experiment bears out that by surveying atmospheric temperatures of two end points and three salient points at the same time it is possible to obtain the atmospheric temperature change rate for different regions of surveying distance,and to make the atmospheric vertical refraction correction for observed value of triangular altitude survey. The standard error of forward and backford altitude difference average value of triangular will reduce about 50%, obviously the method can cut down the influence on triangular altitude survey due to atmospheric vertical refraction.