using Mapserver for on-the-fly raster data?

[Frank Warmerdam]

On 7/6/05, Jeff de La Beaujardiere <jeff2005 at svs.gsfc.nasa.gov> wrote:
> Frank Warmerdam wrote:
> > As of 4.6 (actually it might have been in 4.4 too), MapServer supports
> > the ability to apply classification to non-8bit raster data.
> 
> OK, I have this mostly working in test mode with just a few colors.
> However, there remains a problem that I have not yet solved and may be
> an SRS/EPSG/WMS issue.  The raw binary input file has data from 0 to 360
> longitude, rather than -180 to 180. If my GetMap request has
> BBOX=-180,-90,180,90 I only get data in the East half of the image while
> the West half is blank. Some component apparently does not understand
> that longitude wraps around. I can get a complete image if
> BBOX=0,-90,360,90, but I do need to be able to use negative values for
> longitude.
> 
> Am I missing something, or is there a workaround for this problem?
> Relevant snippets of my mapfile and VRT file are appended.

Jeff, 

Sigh.  I hate world mapping. 

MapServer has no built-in understanding about geographic
coordinate systems wrapping.  There are various workarounds, 
mostly involving treating the image as two seperate images (one 
for the eastern hemisphere and one for the western) but they are
all likely to be pretty clumsy in your context.  Let me know if you
really want to pursue such an option. 

I think the "simpliest" would be to have two VRT files for each target
image, using the above method, and then another VRT file that
mosaics them (using the SimpleSource method instead of raw bands). 

The right solution is for MapServer to be more savvy about world
mapping issues. 

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