The Immersion Analogy


Courtesy of Dr. Jean Serra at School of Mines, Paris




 In this analogy, the topographic structure of the image with the punctured minima is immersed in a lake.  Water penetrates minima and slowly floods all point below water level that forms catchment basins.  At some point, the rising water starts merging with water coming from neighboring catchment basins.  Supposing that this merging can be prevented by constructing dams at the merging sites continuously until the immersion ends, the location of dams corresponds to the ridge top of the topographic structure that can be viewed as watershed line.