1. A method for use in extracting structures of interest from overhead imagery data, comprising: identifying, using a processor, a plurality of groups of pixels in at least one input overhead image of a geographical region, wherein each pixel in each group is adjacent to at least one other pixel in the group, wherein adjacent pixels in each group do not differ by more than a predetermined level of a dissimilarity measure between the adjacent pixels, wherein a plurality of such groups of pixels at each of a plurality of successive predetermined levels of the dissimilarity measure are identified, wherein the groups at one of the predetermined levels are hierarchically related to the groups at an adjacent one of the predetermined levels in a hierarchical data structure, and wherein each group is a first component; and detecting first components in the hierarchical data structure that each include pixels collectively comprising a geometric attribute level greater than a threshold geometric attribute level.