Lab 7 – TINs and DEMs

Unmodified TIN

Modified TIN with lake feature burned in

 This week's lav investigated vector-based Triangular Irregular Networks (TINs) and compared them to the raster-based Digital Elevation Models (DEMs).  These are two elevation/topographic models used in GIS to produce accurate representations of real topographical features.  A major diffrence between the two models is that TINs use a series of triangles from several sample points (nodes) of known elevation.  To illustrate how a lake feature can be "burned" into a TIN model, the figures at right depict an original un-modified TIN and the resulting TIN.  Because the TIN uses points of known elevation, the border of the lake feature constitutes a series of points of known elevations.  Thus, the burned-in lake increases the number of triangles, both inside and out of the lake.  The slope inside the lake is 0 throughout.