Abstract: A Study on SAS Movement Compensation Based on Time Delay and Phase Estimation Abstract One difficulty of SAS (Synthetic Aperture Sonar) imaging lies in that vehicle instabilities within the aperture length affects the coherence of hydrophone data over the length of the synthetic aperture, which results in distorted images and loss of resolution. Influences of movement errors on synthetic aperture sonar image results and the necessity of movement compensation are discussed firstly. Based on analyzing the so-called displaced phase center algorithm, an improved algorithm is proposed. With this method, the time delay is estimated firstly, then the residual phase error. Through this way the movement error range that can be compensated by this algorithm is extended. Some simulation results on computer and experimental results in the test tank using the proposed algorithm are given in the end of this paper. It can be seen from these results that this algorithm compensates the incoherence caused by movement and medium instability effectively and the imaging quality is improved.