[mapserver-users] Mapserver serving up DEM

[Matt Fair]

Hello,
I have been trying to serve USGS DEM data from a geotiff and have been
getting mixed results.  I have been reading some past discussions and
documentation on this subject, and I seem to be missing something.
The documentation is http://mapserver.org/ogc/wcs_format.html#dem

In my map file I have:

MAP
    NAME "USGS"
    STATUS ON
    UNITS DD

PROJECTION
   "init=epsg:4326"
END

  OUTPUTFORMAT
    NAME "GEOTIFFINT16"
    DRIVER "GDAL/GTiff"
    MIMETYPE "image/tiff"
    IMAGEMODE "INT16"
    EXTENSION "tif"
  END

LAYER
  NAME "usgs_ned"
  STATUS OFF
  TYPE RASTER
  DUMP TRUE
  DATA "layers/usgs_ned/-108_34_-102_36.tif"
  PROJECTION
    "init=epsg:4326"
  END
END

END

This produces a white image, meaning it is probably only reading 8 bits.  If
I add  PROCESSING "SCALE=AUTO", then the values are not maxed out at 255,
but vary based on the size of data I am requesting.  So this won't work
either because in my mapping software, as I request smaller and smaller
patches, the elevation data is scaled really weird and is not consistent.

Is there anything I am missing to get 16 bit USGS DEM data to be distributed
via Mapserver?

Any help would be greatly appreciated.

Thanks,
Matt
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