高精度磁测正常场改正和高度改正精度

A DISCUSSION ON NORMAL FIELD CORRECTION AND ALTITUDE CORRECTION OF HIGH-PRECISION MAGNATIC SURVEY

地球磁场强度存在沿纬度方向和高度方向上的变化,在开展高精度磁测工作时,必须进行高度改正和正常场改正。目前普遍使用的改正方法是根据高斯球谐表达式的13级近似式、十级近似式以及一级近似式进行改正的。经计算发现,与高斯球谐表达式的13级近似式相比,当测点与基点的南北方向距离为30 km时,使用十级近似式计算的正常场改正误差为-0.21 nT;使用一级近似式计算的正常场改正的误差随测点与基点的南北方向距离增大而增大,当测点与基点的南北方向的距离大于4 km时,正常场改正误差大于1 nT;使用一级近似式计算的高度改正的误差随测点与基点高度差增大而增大,当测点与基点高度差大于300 m时,误差大于1 nT。

here exists change of gradient for earth magnetic intensity in directions of altitude and latitude,and hence it is needed to carry out altitude correction and altitude correction during the performance of high-precision magnetic survey.The common method for calculating correction values is based on the thirteen-stage approximate formula of the spherical harmonics expression,and there also exist the ten-stage one and the one-stage one.There commonly exists a small error in using the ten-stage one.In comparison with the thirteen-stage approximate formula,there is a small error in using the ten-stage approximate formula： when there is 30 km between the base station and the measuring points,the error for latitude correction is-0.21 nT;nevertheless,there is a large error in using the one-stage approximate formula： when there is 4 km between base station and the measuring points,the error for latitude correction is about 1 nT,and when there is 300 m in height between the base station and the measuring points,the error for altitude correction is about 1 nT.