Abstract: Geometric calibration of sensor is the key part of photogrammetry. ADS40 is POS supported airborne Three-Line-Scanner. The paper introduces the unique POS supported sensor geometric relation of ADS40, and self calibration with additional parameters based on BROWN model. According to ADS40, a set of calibration programs is designed, considering: how to determine the necessity of geometric calibration, how to carry out geometric calibration, and how to verify the validity of the result of the geometric calibration. Experimental results show that the self-calibration of the ADS40 is effective to improve data accuracy and reliability.