  Digital Elevation Model (DEM), while providing a bare earth look, is heavily
used in many applications including construction modeling, visualization, and
GIS. Their registration techniques have not been explored much. Methods like
Coarse-to-fine or pyramid making are common in DEM-to-image or DEM-to-map
registration. Self-consistency measure is used to detect any change in terrain
elevation and hence was used for DEM-to-DEM registration. But these methods
apart from being time and complexity intensive, lack in error matrix
evaluation. This paper gives a method of registration of DEMs using specified
height values as control points by initially converting these DEMs to ASCII
files. These control points may be found by two mannerisms - either by direct
detection of appropriate height data in ASCII files or by edge matching along
congruous quadrangle of the control point, followed by sub-graph matching.
Error analysis for the same has also been done.
