It has been adopted 7 known heights of state-control point in the area in the paper and used second curved surface fitting to calculate GPS sea level of whole grid. The fitting results basically meet the need for oil exploration.
Starting from the problems encountering in GPS net work establishment and linking with the national control points, the rational disposal of observation program for GPS control net work is discussed under such conditions as under the targets , near obstacles, etc The relation accuracy factor concept and betterment way are put forward It has certain guidance in practice
The paper mainly studies establishment of cross-shaped coordinate system of construction area by the national control points which are out of the area. The construction coordinate of the working drawing is calculated. The lofting is implemented with electronic total station to explore its precision.