we introduce the Color-based Catchment

Basin Merging Algorithm, an area-based segmentation approach

that is specifically designed to segment low-altitude

aerial images, as a preprocessing step to 3D reconstruction.

This approach extends the watershed-based Catchment

Basin Merging Algorithm, which is purely geometric,

by introducing color similarity as an additional criterion to

decide on the merging of evolving regions. Experiments performed

with real aerial images of varied nature demonstrate

that this modification eliminates over-segmentation problems

of the existing algorithm, allowing large-scale urban

scenes to be segmented in an accurate, reliable and fully automatic

way.