The Effect of Shift and Drift Errors in 3D Coordinates Extracted from IRS P5 Imagery

Due to high earthquake potential of Iran, the problem of Land Slide has been increasingly investigated in the recent year. This investigations can be performed in absolute and relative measurement of displacements. In the absolute measurement problem, GCPs are always needed while there are no needs to any ground coordinates in relative measurement of Land Slide displacements. One of the methods that can be used tosolve relative problem, is to use RPCs. In this method, pixel coordinates will be observed in both forward and backward stereo images in corresponding epochs, then 3D ground coordinates of observed points will be computed by using RPC coefficients. The next step is compute the displacement by differentiation of 3D ground coordinates in two epochs. The goal of this paper is to investigate the effect of relative RPC shift and drift errors on 3D ground coordinates. In order to reach this goal, two datasets, Roudehenand Damdol with 400 and 43 points respectively, have been used and their relative RPC shift and drift errors are computed. As a result of this research, the effect of this error in x and y directions was measured 1.8 and 9.5 meters respectively. Also the vertical error caused by RPC shift and drift was measured about 0.48 meters in the Roudehen area. The same error in x, y and z directions in Damdol area was measured 1.37, 7.15 and0.4 meters. This results led the conclusion of this research to this issue that RPC shiftand drift error should be necessarily eliminated in 3D reconstruction problem due to its high effect but it will not cause any accuracy issues in Land Slide problem and because of its relative nature it will be eliminated in displacement equations.