IMAGIS Education

IMAGIS Classic

Digital Elevation Models (DEM) are one of the most fundamental aspects of a spatial information system. Often, this "topographic layer" is the base-level data underpinning the entire geographic information system (GIS) structure. 

There are several ways to collect DEM information including (but not limited to):

• Airborne Laser Scanning
• InSAR technology
• Field survey
• Photogrammetry
• Creating the DEM from digitized contour lines (and potentially spot heights), etc.

Supresoft already provides VirtuoZo, one of the world's finest digital photogrammetric systems for generating DEM's from stereo imagery. However, with DEMix, you can just as easily create your DEM from digitized contour lines and spot heights. This method is ideal for DEM creation when stereo imagery is not available, or simply when contours and spot heights are the only (or best) available source data.

Features of DEMix

DEMix is a software suite allowing the generation of DEM's from digitized contours and spot-heights. The features of DEMix are: 

• The ability to create "Workflow Line Points" for describing the terrain automatically from the input data (contours and spot-heights). (N.B. Workflow Line Points can not only be used for creating the DEM, but can also be used in terrain analysis)
• The ability to create DEM's from the input data along with Workflow Line Points
• The DEM generation is an iterative procedure. The iterative convergence is controlled automatically and all of the temporary data of each iteration is stored in a temporary folder
• Gross errors in the input data are generally detected automatically, but will certainly become evident and can be corrected during the DEMix iterations
• Quality control of the generated DEM is indicated in three ways:
• the Z-RMS (height root mean square error) indicates the height errors of the input contours
• an indication is given as to the number of structure points to which the height values are impossible to assign
• a comparison of the input contour lines and the newly generated contour lines from the DEM produced by DEMix
• The proven ability to cater to input contours resulting in a DEMix triangulation including triangles with all three vertices in a horizontal plane (e.g. from shorelines). (N.B. this is a common problem in less robust systems).
• DEMix reads and writes Arc/Info format files: in this environment only one command is needed to process either a single map sheet or to undertake batch processing