[mapserver-dev] RFC-108 : heatmap generation

[Umberto Nicoletti]

On Thu, Jan 30, 2014 at 11:24 PM, Rahkonen Jukka (Tike) <
jukka.rahkonen at mmmtike.fi> wrote:

> Hi,
>
> Not a dev but Mapserver user list is so quiet that I am lurking here also.
>
> I know that the battle is lost and everything that's on a map and is
> visualizing some data is called heat maps. However, it looks like this
> system is mostly for creating kernel density maps
> http://en.wikipedia.org/wiki/Multivariate_kernel_density_estimation
>
> I am not sure if this image generator can even make such heatmaps like the
> salinity map in the beginning of RFC where missing data between the
> measuring points are (linearly?) interpolated. In that map the density of
> salinity measurement stations has no effect on the colour. Also in real
> life even if you measure a hundred times a temperature of +40 degrees from
> very close measuring points, the maximum temperature does not rise a bit
> over +40.
>
> I went through this thinking some time ago when I was making "heat maps"
> about damages (in EURO) done by bears, wolves and elgs with Saga GIS and I got
> corrected that they were kernel density maps. A bit later there was some
> discussion in context of heatmap rendering transformation in Geoserver.
> Here follows a few links.
>
> Man named Martin Davis wrote:
> "Incidentally, after reading whuber's complaint about the misuse of
> the term "Heatmap" I sort of wish I'd called the process KernelDensity
> instead..."
> It was in this mail
>
> https://www.mail-archive.com/geoserver-users@lists.sourceforge.net/msg12418.html
> and whuber wrote his complaints here
>
> http://gis.stackexchange.com/questions/39074/whats-the-best-way-to-produce-a-density-map-from-weighted-points-in-qgis
>
> The Geoserver way to create kernel density maps which are called heatmaps
> is presented here
> http://suite.opengeo.org/opengeo-docs/cartography/rt/heatmap.html
>
>
Interestingly they support any geometry by simply taking its centroid if
it's not a point. Perhaps that is a viable solution for Mapserver too.

Umberto


> Perhaps RFC and in the future the documentation could also mention the
> term density map or density kernel map. The system itself is welcome and I
> am interested in seeing how the problem of creating automatically a good
> looking visualization for changing map scales is solved. Perhaps output
> pixel based interpolation radius and PROCESSING "NORMALIZATION=AUTO" will
> handle that.
>
> -Jukka Rahkonen-
>
> ________________________________________
> Thomas Bonfort wrote:
>
> > Devs,
>
> > please have a look at RFC-108 [1]. The associated code and the RFC are
> > still beta, so there's still plenty of room for modification or remarks.
>
> > best regards,
> thomas
>
> [1] http://mapserver.org/development/rfc/ms-rfc-108.html
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