Vector data smoothing and palettes

[Frank Warmerdam]

On Sat, 12 Mar 2005 16:30:19 +0000, Dan Taylor
<logicalgenetics at gmail.com> wrote:
> Hi,
>
> I'm pretty new to mapserver, but I think I'm making reasonable
> progress.  Have managed to get my head around the vmap0 and gtopo30
> datasets to generate some good results.  However, I am having problems
> displaying raster data nicely when zoomed in.
>
> Basically, the problem is with jagged edges.  I've created about 20
> classes in my map file with a range of different colours to display
> the gtopo30 data, but I still get very jagged edges - especially in
> mountainous areas like the Himalayas or the Rockies.

Dan,

I'm not exactly clear what you mean by jagged edges.  The GTOPO30
data is inherently fairly low res, so in areas of high relief such as mountains
it will tend to look pretty crappy when zoomed in fairly close.  Are you
hoping for some sort of interpolation of the elevation data when zoomed
in past the natural resolution of the elevation data?  I'm afraid that
MapServer does not support any sort of interpolation of raster data.

You could preprocess the GTOPO data to higher resolution using some
external tool, though this will increase the amount of disk space and
not add any *real* information.  The gdalwarp utility can be used to
resample raster data with a bilinear or cubic convolution resampling
kernel.

> Is there a more elegant way to display raster data than using a huge
> set of classes?

No, unfortunately not.  This is definately something I would like to add.

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