Abstract: The accuracy of the radial velocity estimated by the airborne Along-Track Interferometric SAR (ATI-SAR) is affected by the accuracy of different system parameter, such as the interferometric phase biases and the baseline components errors. Therefore, these factors must be calibrated if the higher radial velocity estimation accuracy is required. The calibration methods based on the sensitivity equations are generally used in the interferometric SAR calibration. However, the performance of these methods is limited by the matrix condition number of the sensitivity matrix, which is decided by the location strategy of Ground Control Points (GCP). This study analyses and simulates the condition number of the sensitivity matrix corresponding to the different GCP distribution ways along the swath as well as the different selections of velocities and positions of moving ground control points.