Abstract: To solve the phase unwrapping (PU) problem in areas with spectral aliasing and abrupt topographic changes,the problem of solving the integer cycle number of dual-baseline InSAR phase unwrapping is transformed into a pure integer programming (PIP) problem,and a DEM-assisted pure integer programming phase unwrapping algorithm is proposed.Firstly,a PIP model with the intercept on the vertical axis as the objective function and a ray as the constraint condition is constructed.Then,the branch and bound algorithm of operations research theory is used to solve the optimal integer solution of ambiguity numbers.Finally,on the premise that the true misunwrapping point is extracted by DEM,and the PU is completed by replacing the ambiguity number with the highest frequency in the square window.The feasibility,effectiveness and universality of the proposed algorithm are proved through the comparative experiments of the simulation data and real data with the branch-cut method,the minimum cost flow method,the Chinese remainder theorem algorithm and the clustering analysis algorithm.The algorithm has good unwrapping capability in phase under-sampling areas and terrain mutation area,and weakens the requirement for the mutual prime of the interferogram baselines.

Key words: DEM-aided, phase unwrapping, dual baseline, branch and bound method, pure integer programming