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Post Info TOPIC: Interpolating Rasters

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Interpolating Rasters

There are three different types of elevation data provided by the LAR-IAC: DEM, DTM, and DSM. DEM, or Digital Elevation Model, is basically a bald earth elevation model. DTM, or Digital Terrain Model, is simiar to a DEM but has major terrain features preserved. DSM, or Digital Surface Model, contains everything on the surface including trees and buildings.

In the LAR-IAC delivery the DEM is a grid, which is easily incorporated into ArcMAP, ArcSDE, etc., but the DTM and DSM are points not rasters. There are several methods to convert the point data into a raster. The more common ways of conversion are through interpolation using Inverse Distance Weighting (IDW) or Spline. Another method is to conver the points into a Triangular Irregular Network (TIN) and then convert the TIN into a raster in ArcGIS with the TIN to Raster conversion. Keep in mind that 3D Analyst extension is needed to convert points to a TIN and convert the TIN to a raster, and Spatial Analyst is needed to interpoate using IDW or Spline.

Research for my masters thesis has shown, but not conclusively proven (yet ), that rasters created by converting points to a TIN, then converting the TIN to a raster produces a raster that more closely matches the input points than rasters interpolated using IDW or Spline.

-- Edited by COPGIS at 21:14, 2007-03-08

Brian GIS Coordinator, City of Pasadena | SoCal GIS Founder/Administrator | You don't always have to be having fun to have fun.
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