WCS data misregistered

[Ben Tuttle]

Hi all-
I am working with a global (actually -180 to 180 and -65 to 65) 30
arcsec dataset. I have been making tiles in geotiff format from this
original image and it sets the pixel size as "Pixel Size =
(0.00833333,-0.00833333)".
This seems to be causing some trouble when I make a wcs request as the
image returned has "Pixel Size = (0.00830565,-0.00830565)" or "Pixel
Size = (0.00830204,-0.00830171)", the returned pixel size vaires at
different points on the globe. So the images I am getting back have
the wrong pixel size and as a result are also misregistered. The
result is the same whether I use the tiles or a single global image. I
have attached my mapfile below. Any thoughts, soutions, or questions
that might lead to solutions would be greatly appreciated.


NAME DMSP-Test
STATUS ON
SIZE 864 312
EXTENT -180 -65 180 65
UNITS dd
SHAPEPATH "/mnt/anchor1/eogmaps/data/"
IMAGECOLOR 255 255 255

WEB
  IMAGEPATH "/mnt/anchor1/eogmaps/www/html/tmp/"
  IMAGEURL "/tmp/"
  METADATA
    "wms_title"     "DMSP Demo Server"  ##required
    "wms_onlineresource"
"http://eogmaps.ngdc.noaa.gov/cgi-bin/mapserv.exe?"   ##required
    "wms_srs"       "EPSG:4326"  ##recommended
  END
END

PROJECTION
  "init=epsg:4326"   ##required
END

OUTPUTFORMAT
  NAME GEOTIFF
  DRIVER "GDAL/GTiff"
  MIMETYPE "image/tiff"
  IMAGEMODE "BYTE"
  EXTENSION "tif"
END

SYMBOL
  NAME "BigLine"
  TYPE ellipse
  POINTS
    1 1
  END
END

LAYER
  NAME "Countries"
  METADATA
    "wms_title" "Countries" ##required
  END
  STATUS on
  TYPE polygon
  DATA "world_adm0.shp"
  CLASS
    NAME "Countries"
    STYLE
      SYMBOL BigLine
      SIZE 2
      OUTLINECOLOR 255 75 0
    END
  END # class
  PROJECTION
    "init=epsg:4326"
  END
END # layer

LAYER
  NAME "F152003_stretched"
  METADATA
    "wms_title"    "F152003_stretched"   ##required
  END
  STATUS on
#PROCESSING "SCALE=AUTO"
PROCESSING "SCALE_1=0,63"
TILEINDEX "tiles/F152003_v2_stable_lights_index.shp"
TILEITEM "Location"
#  DATA "F152003_stretched.tif"
  TYPE raster
  PROJECTION
    "init=epsg:4326"
  END
END

LAYER
  NAME "F152003_v2_stable_lights"
  METADATA
    wcs_description "F152003 v2 stable lights"
    wcs_name "DMSP Annual Composite"
    wcs_label "F152003"
    ows_srs "EPSG:4326"
    ows_extent "-180 -65 180 65"
    wcs_resolution "0.00833333 -0.00833333"
    wcs_bandcount "1"
    wcs_formats "GEOTIFF"
    wcs_nativeformat "8-bit GeoTIF"
    wcs_rangeset_name "F152003_v2_stable_lights"
    wcs_rangeset_label "F152003"
    wcs_rangeset_axes "bands"
    wcs_bands_rangeitem "_bands"
    wcs_bands_name "bands"
    wcs_bands_semantic "http://www.ngdc.noaa.gov/dmsp/"
    wcs_bands_refSys "European Petroleum Survey Group (EPSG)"
    wcs_bands_label "F152003"
    wcs_bands_values "VIS"
  END
  STATUS off
  DUMP true
  TILEINDEX "tiles/F152003_v2_stable_lights_index.shp"
  TILEITEM "Location"
  TYPE raster
  PROJECTION
    "init=epsg:4326"
  END
END

LAYER
  NAME "F152003_stretched_wcs"
  METADATA
    wcs_description "F152003 no tiles"
    wcs_name "DMSP Annual Composite"
    wcs_label "F152003"
    ows_srs "EPSG:4326"
    ows_extent "-180 -65 180 65"
    wcs_resolution "0.00833333 -0.00833333"
    wcs_bandcount "1"
    wcs_formats "GEOTIFF"
    wcs_nativeformat "8-bit GeoTIF"
    wcs_rangeset_name "F152003"
    wcs_rangeset_label "F152003"
    wcs_rangeset_axes "bands"
    wcs_bands_rangeitem "_bands"
    wcs_bands_name "bands"
    wcs_bands_semantic "http://www.ngdc.noaa.gov/dmsp/"
    wcs_bands_refSys "European Petroleum Survey Group (EPSG)"
    wcs_bands_label "F152003"
    wcs_bands_values "VIS"
  END
  STATUS off
  DUMP true
  DATA F152003_stretched.lzw.tif
  TYPE raster
  PROJECTION
    "init=epsg:4326"
  END
END

END #Mapfile