Problems with mapserver and oblique projections

[Frank Warmerdam]

Trond Michelsen wrote:
> Hi.
> 
> I'm having some problems getting mapserver 4.4.1 to draw maps in an
> oblique projection.
...
> Does anyone know what I'm doing wrong? Is there something I can do to
> get mapserver to plot all countries in this projection? (Preferrably
> without the wrapping issues).

Trond,

First, there has been a variety of work on the "world mapping" problem
since 4.4.x.  I would encourage you to try again with 4.10.0 and see
which problems remain.

The core problem relates to computation of a spatial filter to use against
the lat/long data to select all the features needed for rendering.  Originally
I believe the corners of the bounding box in the output coordinate system
were reprojected back to the source coordinate system and used to form a new
bounding box.  This works very poorly in world mapping situations such as
yours where the pole (an extreme in lat/long) is in the middle of the
projected space.

Recent versions of MapServer will "sample" through the destination rectangle
to collect an MBR in the source coordinate system if it detects that some
edge points are not reprojectable.  I'm not sure if this will fix your
problem or not.  There have been some other changes for world mapping that
might also prove useful in your case.

If you still have problems in 4.10.x then please register a bug with a
reproducable situation and we can contemplate what to do about it.

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    | President OSGeo, http://osgeo.org