This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.
 Mathematica Import/Export Format

# CDED

 Canadian digital elevation data.Standard format for the distribution of terrain elevation data for the United States.Canadian Centre for Topographic Information (CTI) standard.ASCII format.Typically distributed as a ZIP compressed file.The .dem file extension is often omitted.Stores elevation data as a 1201×1201 raster.CDED is available in 1:50,000 and 1:250,000 scales.The longitudinal grid spacing varies with the latitude of the geographic area.1:50,000 CDED uses a grid spacing of 0.75×0.75 arc second, 0.75×1.5 arc second, or 0.75×3 arc second.1:250,000 CDED uses a grid spacing of 3×3 arc second, 3×6 arc second, or 3×12 arc second.Elevations are expressed in meters relative to mean sea level.
• Import supports the CDED Level 1 standard.
• Import["dir/"] imports a CDED directory and renders it as a topographic map.
• Import["file.zip"] imports from a CDED archive file.
• Import["dir/", elem] imports the specified element from CDED.
• Import["dir/", {elem, suba, subb, ...}] imports a subelement.
• Import["dir/", {{elem1, elem2, ...}}] imports multiple elements.
• The import format can be specified with Import["file", "CDED"] or Import["file", {"CDED", elem, ...}].
• When importing CDED topographic data, Mathematica reads information from multiple files contained in the CDED directory or archive file.
• See the reference pages for full general information on Import.
 "Elements" list of elements and options available in this file "Rules" full list of rules for each element and option "Options" list of rules for options, properties and settings
 "Data" array of terrain elevation values "Graphics" CDED data rendered as ReliefPlot
• Import by default uses "Graphics" for the CDED format.