Server error retrieving coverage via WCS

[Frank Warmerdam]

Vincent J. Troisi wrote:
> I am trying to retrieve an entire layer of a tiled Geotiff mosaic
> using the WCS protocol. In some cases if I request a subset of the
> layer, I am successful. I am unsuccessful when I near a request the 
> entire area.
> The error is:
> 
>> The server encountered an internal error and was unable to complete 
>> your request.
 >>
>> Error message:
>> Premature end of script headers: <name of the WCS cgi script calling 
>> mapserv>

Vincent,

My guess is that the request is large and mapserver is running out of
ram and crashing.  However, MapServer should detect failed mallocs
especially for large buffers.  I'd encourage you to either try and debug
the problem in situ-or submit a bug report we can use to reproduce the
problem.

If it is a memory problem then reproducing the problem may depending
on various machine/os issues.

> We are using mapserver 4.6. The layer is 16-bit raster. Each pixel 
> represents
> a 125x125m surface resolution. The extend is
> -3174450,-2816050,2867175,2406325
> 
> I attempted to retrieve the layer/image with ResX and ResY set to 250
> (enhancing the resolution by 2). The request was successful, but the
> values in the retrieved file were all 0.

Note, I'd call reducing the resolution to 250x250 degrading rather
than enhancing the image.  However, if you can provide a bug report
where we can reproduce this problem then we can fix it (assuming it is
a mapserver or gdal problem).   I don't believe it is expected behavior.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org