Problems with mapserver and oblique projections

[Trond Michelsen]

On Wed, Nov 15, 2006 at 01:09:49PM -0500, Frank Warmerdam wrote:
> Trond Michelsen wrote:
>> I'm having some problems getting mapserver 4.4.1 to draw maps in an
>> oblique projection.
> 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.

Ah, OK. Thank you. We have installed mapserver from a .deb package for
Debain Sarge, and I don't think there's a newer version available. If
possible, I'd like to avoid building from source, but it seems that
this is the only alternative in this case, so I'll give it a shot.
 
> 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.

Thanks. I'll give it a try, and let you know how it turns out.
 
> 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.

Sure.

-- 
Trond Michelsen