In GPS control survey,as if relevant definition parameter of local independent coordination system were unknown,the constraint adjustment couldn′t adjust,and that can do nothing but can apply coordinate translation method to solve the local coordinate of unknown points;in TGO system,the point calibration is used to solve this problem.

Hereby,this paper introduced three kinds of known points\' reliability check methods,such as regression analysis,actual measurement baseline comparison and constraint adjustment method.

A study on the influence of datum points on the precision of restrained adjustment results of GPS engineering networks has been carried out on the basis of examples.

Approve- useful index of the datum point of the bount adjustment is proposed An accurate, high - efficiency, reliable approve -useful methods are also discussed, which makes use of the tested variance of the no - bound adjustment and the reliability - analytical matrix, by which once all designing coincidence - point is judged.