Problem with Graticule and polar stereographic projection

[Martin Weinelt]

On Thursday 19 May 2005 01:44, Steve Roberts wrote:
> Hello,
> 
> I am having problems with using a graticule on a polar stereographic
> projection. When the map is centered near the north pole all the lat/lon
> lines disappear from the center of the image. You can find an example at:
> 
> http://www.joss.ucar.edu/cgi-bin/catalog/mapserv?mode=map&layer=GRID&map=/web/catalog/bug/grid_test.map
> 
> 
> I'm also seeing spurious straight line segments that parallel the latitude
> lines. This site is using mapserver-4.2.3 on SunOS 5.9 sparc SUNW,Ultra-6.
> However I see the same problem with mapserver-4.4.2 on linux Mandrake 10.1.
> Any help in solving this problem would be greatly appreciated. Below is the
> sample grid_test.map file.
> 
> Thanks,
> Steve

Steve,

I am struggling with a related problem for quite a while now
(since 3.6). 
 
Reprojecting lat/lon-data such as shapefiles or WFS-data to 
areas around the poles result in unpredictable 
rendering by mapserver. In our case it is Lambert Azimuthal
Equal Area in polar aspect, but I remember some postings
regarding Orthographic as well. Graticule layers do not 
work as expected for these projections as well and look 
similar to your example.

Parts of the data (or graticule) get 'clipped' by Mapserver
for specific map extents. When zooming to smaller areas 
data and graticule show up. But with mapextents including
the pole(s) things get messed up.

I guess reprojecting itself is not the problem because 
I can use Proj-based utilities to project my data in advance
and they show up just fine. I have the impression that mapserver
- before rendering - decides which features fall outside the
mapextent, discards these features and at this stage is not
always right. Just a guess.

Cheers, Martin