[mapserver-users] Multi-Resolution Terrain Map File

[Enzmann, Alexander R.]

How do I construct a map file that can handle different resolutions of terrain, with fallback to lower resolution when a no-value is found?  In Google Earth Fusion, I can specify multiple terrain sources and tell it which value(s) represent missing data, and it will then process the terrain, checking for availability of each type of terrain, falling back if there isn't any in a geographic area and falling back if there is missing data.

For simple fallback based on area coverage, I can use a map file like the one below (using 30 Arcsecond SRTM and 1 Arcsecond DTED).  Now, what would I need to do to have it use/interpolate data from the 30 Arcsecond values when there is a missing data/NODATA/hole in the DTED?  In the file below, gdaltindex has been used to generate the coverage shapefiles.

The example below is a simple one, and it would be really helpful to be able to have multiple terrain sources and a way to automatically fill voids the same way that transparency works with raster image layers.  Specifying that terrain values are posts and not pixels would be good too, but lower priority.

Xander

MAP
  NAME "srtm"
  EXTENT -180 -90 180 90
  SIZE 512 512
  UNITS DD
  IMAGETYPE bil

  PROJECTION
    "init=epsg:4326"
  END

  OUTPUTFORMAT
    NAME "bil"
    DRIVER "GDAL/EHdr"
    MIMETYPE "image/bil"
    EXTENSION "bil"
    IMAGEMODE INT16
  END

  OUTPUTFORMAT
    NAME "bil16"
    DRIVER "GDAL/EHdr"
    MIMETYPE "application/bil16"
    EXTENSION "bil"
    IMAGEMODE INT16
  END

  OUTPUTFORMAT
    NAME "gtiff_16"
    DRIVER "GDAL/GTiff"
    MIMETYPE "image/tiff"
    EXTENSION "tif"
    IMAGEMODE INT16
  END

  WEB
    IMAGEPATH "/tmp/"
    IMAGEURL "/tmp/"
    LOG "/tmp/srtm.err"
    METADATA
      wms_title "SRTM Terrain"
    END
  END

  #
  # Coarse (30 ArcSecond) terrain.  There is worldwide coverage, so this
  # is good for areas uncovered by SRTM data, as well as for high
  # scale values.
  #
  LAYER
    NAME "srtm"
    TILEINDEX "SRTM30/bathmetry.shp"
    TYPE RASTER
    PROCESSING "RESAMPLE=BICUBIC"
    STATUS ON

    METADATA
      "wms_title" "SRTM 30 ArcSecond Bathmetry"
      "wms_group_title" "srtm30"
      "wms_srs" "epsg:4326"
      "wms_style" "Default"
      "wms_extent" "-180 -90 180 90"
    END

    MAXSCALEDENOM 1000000000
    MINSCALEDENOM         10
  END

  #
  # Moderate resolution (1 ArcSecond) terrain.  Coverage is available worldwide
  # for most land areas between latitudes -60 and +60.
  #
  LAYER
    NAME "srtm"
    TILEINDEX "srt2f_1/srt2f_1.shp"
    TYPE RASTER
    PROCESSING "RESAMPLE=BICUBIC"
    STATUS ON

    METADATA
      "wms_title" "SRTM 1 ArcSecond Bathmetry"
      "wms_group_title" "srtm30"
      "wms_srs" "epsg:4326"
      "wms_style" "Default"
      "wms_extent" "-180 -60 180 60"
    END

    MAXSCALEDENOM 1000000
  END

END

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