[Gdal-dev] Question on building external overviews

[Frank Warmerdam]

Stephen Woodbridge wrote:
> 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.

Steve,

I don't see any obvious problem with the process.  When you say they are
grey in mapserver, do you mean "greyscale" or a single constant grey?

If you can reproduce the problem with a small dataset I would be happy to
try it here and comment.

Best regards,
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