Digital Terrain Model
A digital Terrain Model (DTM) is a numerical representation of the configuration of the terrain consisting of a very dense network of points of known X, Y, Z coordinates. Modern surveying and photogrammetric equipment enable rapid three-dimensional data acquisition.
A computer processes the data into a form from which it can interpolate a three-dimensional position anywhere within the model. Think of a DTM as an electronic lump of clay shaped into a model representing the terrain. If alignment was draped on the model and a vertical cut made along the line, a side view of the cut line would yield the alignment’s original ground profile.
If vertical cuts were made at right angles to the alignment at certain prescribed intervals, the side views of the cuts would represent cross-sections. If horizontal cuts were made at certain elevation intervals, the cut lines when viewed from above would represent contours. A DTM forms the basis for modern highway location and design. It is used extensively to extract profiles and cross-sections, analyze alternate design alignments, compute earthwork, etc
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