Abstract: According to selected ground control points,an optimal trian-gular net is automatically constructed.Then,a system of coefficients thattransforms triangular elements are calculated.For avoiding the possiblefailure of this calculation,some long edges of the triangles are repartitioned.Determiuant decision condition and dynamic Searching Sequence are used,sothat the geometry distortion correction is speeded up and arithmatical over-flow is avoided.In addition,a treatment for the boundary is prsented.