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Vis > data > datasets > "Smith & Sandwell" Topography

"Smith & Sandwell" Topography

A 1/30° (nearly) global elevation (topography and bathymetry) dataset from UCSD, created by David T. Sandwell, Walter H.F. Smith, et al., is available for general use at GFDL. It was assembled from many different sources and its main goal seems to be greatly improved bathymetry over the older ETOPO5 and TerrainBase datasets.

This apparently unnamed dataset consists of 10800x6336 gridpoints with uniformly spaced longitudes ranging from .0167°E to 359.983°E and Mercator spaced latitudes ranging from 72.0009°N to -72.0009°N; the netCDF version (created at GFDL) runs from south to north instead. The elevations are expressed in integer meters with positive values above sealevel and negative values below. The files are located in "/archive/hnv/SS_topo/" (GFDL only):

  • SS_topo_6.2.img
    		•  Original IEEE (big-endian, 16-bit integers) version of the dataset.
  • README
    		•  Description of the format of the IEEE version.
  • mygrid_sand.m
    		•  MATLAB script for viewing the dataset.
  • SS_2min_topo.nc
    		•  NetCDF version containing the data as 16-bit integer values (>130MB; only slightly larger than the IEEE version). Although, these values are "packed", they are identical to those in the original plain IEEE version since the variable's add_offset=0 and scale_factor=1.
  • SS_global_topo.png  
    		•  PNG image (3825x2350, 24-bit, ~15.6MB) of the entire dataset. This image and the regional ones below have exactly the same contents as the original TIFF images available from UCSD via FTP. PNG, however, provides better compression than TIFF while preserving the integrity of the 24-bit data.
    SS_global_topo.png
  • SS_topo*.png
    		•  The global image above doesn't have enough pixels to represent all the gridpoints in the dataset, so there are also 16 regional PNG images (3300x2100, 24-bit, ~6.7-9.2MB each). Note: The continental outlines and rivers are not part of this dataset.
    SS_topo1.pngSS_topo2.pngSS_topo3.pngSS_topo4.png
    SS_topo5.pngSS_topo6.pngSS_topo7.pngSS_topo8.png
    SS_topo9.pngSS_topo10.pngSS_topo11.pngSS_topo12.png
    SS_topo13.pngSS_topo14.pngSS_topo15.pngSS_topo16.png
    Here's a cropped section from "SS_topo8.png" showing the full resolution that the data provides. This more manageable image is only 946x874 (~1.5MB), which fits easily on the screen. It also has a colorbar which shows the colormap used for all the images. Although the colormap only goes from 7000m to -7000m, the actual range of the entire dataset is 8123m to -10795m.

    Note: In case it's not obvious, each small topography image is a link to its corresponding full-size version. The full-size versions (excluding the cropped one) are larger than the screen, so they will be scaled to fit the screen if viewed with XV. Use ImageMagick's display to view them at their actual size with panning capability. They (excluding the cropped one) may be far too memory-intensive to view on machines with only 32MB (hint: run hinv to see how much memory is installed on an SGI)! Also note that the full-size versions may have migrated to tape since they're on archive (again excluding the cropped one which is always available on FTP), so please check before downloading.

    Lasted modified: Tuesday, 09-Jan-01 15:26:54 EST

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    last modified: February 20 2004.