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Mathematica Import/Export Format

GTOPO30

GTOPO30 global topographic data.
United States Geological Survey (USGS) standard.
Distribution format for a global digital elevation model (DEM) with 30-arc-second grid spacing.
Binary format.
Typically distributed as a compressed archive of multiple files.
Uses a horizontal grid spacing of 30 arc seconds (1/120 degrees) or approximately 1 kilometer.
Developed 1993-1996 by the USGS Center for Earth Resources Observation and Science.
  • Import fully supports the GTOPO30 format.
  • Import["dir/"] imports a GTOPO30 directory and renders it as a topographic map.
  • Import["file.tar.gz"] imports from a GTOPO30 archive file.
  • Import["dir/", elem] imports the specified element from GTOPO30 data.
  • Import["dir/", {elem, suba, subb, ...}] imports a subelement.
  • Import["dir/", {{elem1, elem2, ...}}] imports multiple elements.
  • The import format can be specified with Import["file", "GTOPO30"] or Import["file", {"GTOPO30", elem, ...}].
  • When importing GTOPO30 topographic data, Mathematica reads information from multiple files contained in the GTOPO30 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
  • Import elements:
"Data"array of terrain elevation values
"Graphics"GTOPO30 data rendered as ReliefPlot
  • Import by default uses "Graphics" for the GTOPO30 format.
  • Metadata elements:
"DataFormat"data type used in the file for storing elevation values
"Dimensions"size of the elevation data array
"SpatialRange"range of geographic coordinates, given in decimal degrees
"SpatialResolution"grid spacing in arc seconds
  • Import["file.tar.gz", "ElevationRange"] gives the range {zmin, zmax}of elevation values in meters.
  • Import["file.tar.gz", "SpatialRange"]gives the bounding coordinates of the geographic region covered by the file as an expression of the form {{latmin, latmax}, {longmin, longmax}}.
BoxRatiosAutomaticeffective 3D bounding box ratios
ColorFunction"Cartographic"how to determine the color of surfaces
ColorFunctionScalingFalsewhether to normalize the elevation values supplied to the color function
DataRangeAutomaticthe range of latitude and longitude values to assume for the data
DataReversedFalsewhether to reverse the order of rows
ImageSizeAutomaticthe overall size of the image
LightingAngleAutomaticthe effective angle from which simulated illumination is taken to come
  • Advanced options:
"DefaultElevation"0elevation value taken for sea-level data points
"DownsamplingFactor"10integer factor by which the number of latitudinal and longitudinal data points is reduced when importing
  • GTOPO30 internally represents the ocean elevation as -9999 meters.