In this paper, a dedicated phase unwrapping approach, taking a priori information into account and combining multi-scales local frequencies of the interferometric phase, is developed in order to get around of the discontinuity and aliasing problems. In this approach, the interferogram is characterized by local frequency of the phase. The multi-scales local frequencies of the interferometric phase are estimated and fused to the local frequency at the optimal scale. This optimal scale, the lowest resolution scale allowing phase unwrapping without aliasing problem, is determined from the a priori displacement information. The application is performed on the displacement measurement of the 2005 Kashmir earthquake. The a priori displacement information is issued from a deformation model. The advantages of this approach are highlighted by the obtained results.