An inspection system is disclosed. In one embodiment, the inspection system includes an interferometer sub-system configured to acquire an interferogram of a sample. The inspection system may further include a controller communicatively coupled to the interferometer sub-system. The controller is configured to: receive the interferogram from the interferometer sub-system; generate a phase map of the sample based on the received interferogram, wherein the phase map includes a plurality of pixels; select a sub-set of pixels of the plurality of pixels of the phase map to be used for phase unwrapping procedures; perform one or more phase unwrapping procedures on the sub-set of pixels of the phase map to generate an unwrapped phase map; and generate a surface height map of the sample based on the unwrapped phase map.