Figure 1
From: Visual data mining based on differential topology: a survey
Analyzing a discrete elevation model. Features of differential topology are extracted by tracking the topological change in cross-sectional contours with respect to the height. The boundary of the yellow region represents one of the cross sections of the terrain surface at height 160: the region itself corresponds to height ≥160 and corresponds to the subgraph in the join tree marked yellow in Figure 3.