At present, GPS plane control net is widely applied, but the GPS elevation is not used widely. The people expect that the GPS elevation surveying can take the place of the conventional leveling.
Since leveling is one of the important branches of surveying, its' software designing has great realistic significance.
水准测量是测绘学科的一个重要分支，开发水准测量程序具有重要的现实意义。
3
When surveying major diameter and higher hanging pipeline, common trigonometric leveling can't meet precision requirement, but tangent method surveying can meet precision requirement.