A refined marker controlled watershed for building extraction from DSM and imagery

In this paper, we present a refined marker controlled watershed segmentation of the gradient of a digital surface model (DSM) to extract the buildings. To remove the effect of terrain, we first derive a digital terrain model (DTM) from the DSM by geomorphology filtering, and then generate a normalized DSM (NDSM). Since urban appearance is complex, building extraction is implemented through several stages. In the first stage, the large buildings are extracted according to the thresholds of the height and the area, to avoid being separated at watershed. Then the small buildings are segmented by watershed with markers. Finally, orthogonal imagery is used to remove the trees according to the colour principle. A case study is carried out on a DSM of a region of Kounan, Japan with a spatial resolution of 0.5 m. The experiment shows the effectiveness of this method.