Indirect contouring is the family of surveying methods that determine a terrain's contours not by physically walking the contour line (direct method) but by measuring the X, Y, and Z coordinates of a set of terrain points and then interpolating where each contour interval falls between them; grid, radial-line, and total-station observation are three ways of collecting that point data. A Digital Elevation Model (DEM) is the discretized, computer-storable representation of the same continuous topography — a grid or raster of average elevation values (or, in the Triangulated Irregular Network / TIN form, a set of observed points plus an explicit topological/neighbor relationship) — that substitutes for the analog contour line because a computer cannot natively store a continuous curve. Both representations belong to surveying/geomatics and underlie downstream terrain-analysis applications such as contour gradients, longitudinal profiles, catchment (watershed) delineation, reservoir-volume computation, and inter-visibility analysis.
Indirect contouring is the family of surveying methods that determine a terrain's contours not by physically walking the contour line (direct method) but by measuring the X, Y, and Z coordinates of a…