Abstract: PS InSAR technique has a special advantage is in monitoring small crustal displacements, but its application is severely restricted by the number of images. This paper selects a town named Huailai which has a stable deformation rate as the test area. We choose three models based on the differences of reference image and height corrections to process 15 ASAR images with PS technique. Additionally, we analyse the errors of unwrapped phases, corrections of baselines and point heights. The result shows that for small stacks, the phases are unwrapped falsely on some points as well as the height corrections,but the deformation estimation is right in the whole. Among the three models, the result of Model Two (Multi-Reference Single Regression)is the most reliable. The quality of points is very low on the whole for small stacks, and the reliability of solution can be increased by lowering the phase standard deviation threshold.

Key words: PS InSAR, Reference image, Height corrections, Unwrap phase, Small stacks