Improved SITAN algorithm in the application of aided inertial navigation

In order to solve the drawback that navigation error of Sandia Inertial Terrain Aided Navigation (SITAN) algorithm diverges easily if the initial Inertial Navigation System (INS) error is big. The contour matching algorithm for the initial optimization is proposed. The initial matching error can be reduced and match position points can be formed. And then SITAN algorithm is introduced and the optimal estimation position can be obtained. The contour matching algorithm makes full use of the characteristics that INS has high precision and heading error is small during a short period. The optimal distance function differences are constantly found between two contours and the initial matching points are obtained. Then the precise matching points are obtained by SITAN algorithm. The terrain entropy is used as the terrain discriminant index. Simulation result shows that when the INS track error is big, the matching precision is improved by improved SITAN Algorithm.