WFS layer projection problem

[Frank Warmerdam]

On Mon, 14 Mar 2005 16:09:07 +0100, Martin Weinelt
<mweinelt at planiglobe.com> wrote:
> From the logs of the WFS-server we can see, that the mapserver
> CGI sometimes sends strange bounding boxes to the WFS, which
> do not really cover the area shown by the map.
>
> Is there anything special with LAEA and mapserver (proj4). Has anyone
> encountered s/th similar? Where should we start searching for
> potential solutions to this problem?

Martin,

There are many challenges in global scale mapping with MapServer or
many other GIS packages.  In particular, spatial queries are normally
represented as a bounding box.  If you reproject a bounding box
from a projection like LAEA, near the pole, to decimal degrees, you can
encounter many quirky situations where the resulting rectangle does
not accurately represent the same area of the earth due to the
different natures of the two coordinate systems (for instance the specialness
of the north pole in geographic coordinates).

There is a mapserver wiki topic discussing some of the challenges of
global scale mapping, though unfortunately we can't add to it anymore.

I don't have any useful suggestions on how to resolve the problem for
your particular case.  The proper solution would *likely* be to make
the MapServer bounding-rect reprojection function know alot more
about the nature of coordinate systems.  But that is a hairy area.

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