SCALGO Model software constructs and simplifies massive terrain models.

A Delaunay triangulation of the (2D projection of the) input points set is used to construct the TIN because it attempts to avoid skinny triangles by maximizing the minimum angle of all the triangles. The triangulation is constructed on all the input points to avoid artifact such as those that can e.g. be introduced when using tiling. If the input point set is given in the LAS file format, where each point is assigned a class, then the module supports constructing the TIN on specific classes

Example of how an extra point in the point set above can introduce three large triangles. These triangles can be ignored in the interpolation since they have large side lengths.

As illustrated in the above-right example, no interpolation is performed in (the non-shaded) cells where the center is not contained in a triangle, that is, elevation values of raster cells outside the convex hull of the input points are undefined (given a nodata value). Actually, as illustrated in the figure on the right, it is sometimes desirable to ignore large triangles in the interpolation step. For instance, large lakes in the terrain may result in large triangles in the interior of the model, and inlets and fjords may result in large triangles along the boundary of the model. Interpolating over these triangles will often not yield appropriate elevation values. Optionally, it is therefore possible to ignore all triangles where the length of any of the three sides exceeds a given threshold.

Example of a raster where a cell is colored red if the distance to the nearest input point is longer than 1 meter is overlaid with an orthophoto. It is clearly seen that the input lacks points on buildings and vegetation.

As illustrated on the figure on the right, the large valued cells in the coverage raster corresponds to regions that are sparsely covered with input points and thus are the regions where an interpolated terrain model is less reliable.

The Aggregate module supports a number of functions, including mean, min, max and sum. If C or R is not divisible by w some of the (boundary) cells in the input raster will be ignored. Optionally, the module can add nodata cells to the input raster such that C and R are divisible by w and no input cells are ignored.

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).