Analysis and Discussion of GPS Elevation Replacing the Five Grade Leveling

In recent years,the Global Positioning System is widely applied in the fields of Surveys.The horizontal precision in GPS surveying has been high,which can satisfy the demand of precision in some horizontal control network.But the precision of height in GPS surveying needs a further improve,so the study of GPS height transform system has important meanings for the application of GPS.This arises by the disagreement between GPS height system and level height system,so the results of GPS surveying must process the transform of height system,which Can satisfy the need of engineering.The paper mostly studies height transform and particularly discusses mathematic fitting model.At last,fitting of a regional GPS elevation and comparative analysis of the accuracy of the standard height,it proposed the use of GPS observations plus a known elevation point of seeking to be determined point of elevation fitting way to describe grade GPS network geometry fitting height can reach the standard of ordinary measurement accuracy.