WCS: server fails with a small coverage

[Frank Warmerdam]

On 10/18/05, José Vte Higón <higon_jos at gva.es> wrote:
> Hi list,
> I'am using mapserver wcs 4.6.0, when I request a coverage with a small size
> (an extent quite big),
> the server returns this error:
>
> msDrawMap(): Image handling error. Unable to initialize image.
> msPrepareImage(): General error message. Image dimensions not specified.
> msCalculateScale(): General error message. Invalid image extent,
> minx=-1.000000, miny=-1.000000, maxx=-1.000000, maxy=-1.000000.
> mapserv(): Web application error. No way to generate map extent.
>
> This is the request:
> http://gruposigp2/cgi-bin/wcs?COVERAGE=quickbird3&CRS=EPSG:32630
> &BBOX=742806.4,4264938.3,753600.4,4268018.3
> &bands=1,2,3&FORMAT=GEOTIFF_INT16&WIDTH=18&HEIGHT=5
>
> In order to prevent this error, I have tried to filter this layer when the
> scale is bigger than 1000000 meters:
> ...
> UNITS METERS
> MAXSCALE 1000000
> ...
> but, the error is still happening!

José,

This error is typically reported when the computed internal WIDTH or
HEIGHT are zero.  This might be happening in your case if the BBOX
is substantially larger than the extents of the data, such that the
final result HEIGHT would less than 1.

BTW, I don't think it is legal according to the WCS protocol to request
data beyond the extents of the coverage.  Are you doing that?

However, I am not sure of this analysis.  For us to really dig into this
I think you will need to provide everything we need to reproduce the
problem.

 o Map file  (cut down to just what is needed for this problem).
 o Data file(s).
 o the QUERY_STRING we can pass on the commandline to reproduce
    the problem.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent