[Gdal-dev] Re: Parzen Window Kernel Density Filter

[Frank Warmerdam]

On 1/28/06, Bill Binko <bill at binko.net> wrote:
>
> I've found several references that describe the Parzen Window Kernel
> Density method,
...
> So!  I would like to write a filter that takes a vector point set (OGR
> Data Source, probably), a display window, and some parameters such as
> resolution, color range values, etc. and produces a raster output through
> GDAL.
>
> I would like to invoke this through mapserver (PHP/Mapscript) and have it
> look like a layer that can be turned on/off etc.
>
> I realize this is ambitious, but I think its very doable, and worthwhile.
> If there is desire, I would be happy to release it to others who are
> interested (either through GDAL, or other means).
>
> So, here are my questions:
>
> 1) Is this sane?  I know there are alternatives, but they all (so far)
> seem to involve calling out to tools that are not highly suitable for
> real-time web-based mapping.

Bill,

I think I won't touch the sanity issue. :-)

> 2) Are there examples of filters that sit between GDAL and OGR like this:
> Browser->PHP/Mapscript->Mapserver->GDAL->EXAMPLE FILTER->OGR

No, I can't think of anything setup this way currently.

If you wanted to be really fancy, you could implement
your algorithm in such a way that it is a kind of virtual layer
in the VRT driver.

Alternatively, you could just have mapscript invoke a function
(or an external program) for your selected area and parameters
and generate a temporary file for use in the map rendering.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent