DEM back drop in MapServer

[Frank Warmerdam]

On Wed, 12 Jan 2005 15:59:29 +0000, Norman Barker <normanb at comsine.co.uk> wrote:
> Would there be a way to render this in mapserver natively (so that the
> height fields are rendered
> by an internal palette) and displayed to the user as a backdrop?
>
> Or do I have to define the palette myself in an external program and
> then use it in MapServer?
>
> Any help or advice appreciated by anyone else who has created a DEM
> backdrop.

Norman,

First, there are free locations from which you can
download GTOPO.   No harm in paying for it if you
want of course.

But the answer to your question is that MapServer
does not currently have a means of internally building
a color ramp for DEMs other than defining many
CLASSes for each descrete color you want.   I would
suggest pre-processing the file to 8bit externally
and externally creating a pallete for the file - if you
just need the GTOPO data for display purposes.

If you want WCS access, or raster query such an
approach might not be appropriate.  In that case
you could define many classes to give a color ramp
effect.  30-40 classes should be sufficient.

I would eventually like to implement a mechanism
to define a color ramp in MapServer for rasters
but that is not likely to happen in the short term.

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