A new concept: critical number of looks for multilook processing method for InSAR noise suppression

Interferometric synthetic aperture radar(InSAR) is usually employed to provide altitude information of terrain. There are many factors to cause interferogram noise and the noise decreases height measurement accuracy of InSAR. In this paper, Multilook processing technique, which is used to reduce interferogram noise in InSAR, is studied. And a new concept - critical number of looks for multilook processing is proposed. The number of looks must be smaller than critical number of looks when multilook processing is applied to the interferogram noise suppression. The new concept benefits the multilook processing for InSAR noise suppression. With the knowledge of critical number of looks, the proper number of looks can be chosen for InSAR multilook processing to reduce the interferogram noise. The equations of range and azimuth critical numbers of looks are presented for both single baseline spaceborne InSAR and multibaseline spaceborne InSAR. The critical number of looks can be obtained from these equations. In the end, multilook processing with different numbers of looks is applied to InSAR simulated data and the results show the validity of critical number of looks in InSAR.