SCALGO Simplify software simplifies the topology of massive raster terrain models.

Modern detailed (and thus massive) terrain models often contain a large number of depressions that may adversely affect terrain analysis applications (such as surface flow modeling) and derived products (such as contour lines). This leads to the need for terrain model simplification, but often such simplification is done in a very coarse or ill-specified (heuristic) way that may lead to the loss of important features and thus problems in subsequent applications. In contrast, the topological simplification module simplifies a terrain model in a fully-specified way. This leads to significantly improved derived products and analysis results.

For example, when modeling how water flows on the surface of a raster terrain model, river networks are often extracted as the cells that transport a lot of water (blue on the below figures). In this case, depressions in the terrain will impede flow leading to a disconnected river network (left figure). Therefore depressions are often filled before modeling flow to simulate a situation where no surface water gathers in depressions (middle figure). However, filling all depressions can lead to loss of a lot of detail (and very large flat areas) and therefore unrealistic river networks; filling all depressions in the above-right terrain example would remove most of the terrain detail. The topological simplification module can be used to only remove (fill) "insignificant" depressions, leading to more realistic river networks while maintaining most of the terrain detail (right figure).