[Gdal-dev] Question on building external overviews

[Stephen Woodbridge]

Hi guys,

I took this approach to building external overviews, but all my images 
seem to be gray in mapserver and appear to be all nodata values in the 
file. Any idea what I'm doing wrong here?

I have a directory of of 16x16 tiles that fill a one degree block.
I want to make 4x4 overview files with 4x4 of the original tiles.
ie: 4x4 original tiles into 1 overview

So for the first tile, I create the output tile like this

gdal_translate -of GTiff -co \"TILED=YES\" -outsize 3200 3200 -a_srs 
EPSG:4326 -a_nodata 0 -a_ullr $top $left $bot $right $inf $outf

then for each additional tile I mosaic them into $outf like this:

gdalwarp --config GDAL_ONE_BIG_READ ON -srcnodata 0 -rc -wm 150 $inf $outf

Any help would be appreciated.

Thanks,
   -Steve

Here is what the $outf looks like:

[swoodbridge at booboo tile-repository]$ gdalinfo OV1/B-100_27/T-100_27-03.tif
Driver: GTiff/GeoTIFF
Size is 3200, 3200
Coordinate System is:
GEOGCS["WGS 84",
     DATUM["WGS_1984",
         SPHEROID["WGS 84",6378137,298.2572235629972,
             AUTHORITY["EPSG","7030"]],
         AUTHORITY["EPSG","6326"]],
     PRIMEM["Greenwich",0],
     UNIT["degree",0.0174532925199433],
     AUTHORITY["EPSG","4326"]]
Origin = (28.000000000000000,-100.437500000000000)
Pixel Size = (-0.000078125000000,0.000078125000000)
Metadata:
   AREA_OR_POINT=Area
Corner Coordinates:
Upper Left  (      28.000,    -100.438) ( 28d 0'0.00"E,100d26'15.00"S)
Lower Left  (      28.000,    -100.188) ( 28d 0'0.00"E,100d11'15.00"S)
Upper Right (      27.750,    -100.438) ( 27d45'0.00"E,100d26'15.00"S)
Lower Right (      27.750,    -100.188) ( 27d45'0.00"E,100d11'15.00"S)
Center      (      27.875,    -100.312) ( 27d52'30.00"E,100d18'45.00"S)
Band 1 Block=256x256 Type=Byte, ColorInterp=Red
   NoData Value=0
Band 2 Block=256x256 Type=Byte, ColorInterp=Green
   NoData Value=0
Band 3 Block=256x256 Type=Byte, ColorInterp=Blue
   NoData Value=0