GTOPO30

  • Import fully supports the GTOPO30 format.
  • Background

      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 19931996 by the USGS Center for Earth Resources Observation and Science.

    Import and Export

    • 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/"] renders GTOPO30 data using ReliefPlot.
    • 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, the Wolfram Language reads information from multiple files contained in the GTOPO30 directory or archive file.
    • See the reference pages for full general information on Import.
    • ImportString supports the GTOPO30 format.

    Elements

    • General Import elements:
    • "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"DEM file rendered as ReliefPlot
      "Image"raw DEM data as an image object
      "ReliefImage"DEM file rendered as ReliefImage
    • 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
      "ElevationRange"range of elevation coordinates, given in meters
      "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}}.

    Options

    • General Import options:
    • 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 meters.

    Examples

    Basic Examples  (3)

    Import a GTOPO30 file, rendering it as a relief plot:

    In[1]:=
    Click for copyable input
    Out[1]=

    Show the import elements available for this file:

    In[1]:=
    Click for copyable input
    Out[1]=

    Import the latitude and longitude range of the coordinates stored in the file:

    In[1]:=
    Click for copyable input
    Out[1]=

    See Also

    "CDED"  "SDTSDEM"  "USGSDEM"

    Introduced in 2007
    (6.0)
    | Updated in 2010
    (8.0)