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AW3D (top) and SRTM data (bottom)



DEM/DTM is a digital model or 3D representation of a terrain's surface. It may be represented as  grid data which includes raster format, interpolated values and have large storage for network analysis or in TIN (Triangulated Irregular Network) data which includes-

 • Irregularly distributed nodes and lines with three dimensional coordinates (x, y, and z).
 • Arranged in a network of non overlapping triangles (triangular tessellation).
 • Based on Delaunay triangulation.
 • Density of points α variation in surface heights.
 • (+) points provide accurate representation of terrain.
 • (+) fewer points are needed.
 • (-) less suited for analysis of surface slope, aspect and network analysis.



The Japan Aerospace Exploration Agency (JAXA) has started to process the precise global digital 3D map using some 3 million data images acquired by the Panchromatic Remote sensing Instrument for Stereo Mapping (PRISM) on-board the Advanced Land Observing Satellite “DAICHI” (ALOS), which will be useful in mapping, damage prediction of natural disaster, water resource research etc. The digital 3D map consists of a DEM (or DSM) and ortho-rectified images (ORI) that indicate geolocation.


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