[mapserver-dev] RFC-108 : heatmap generation

[Rahkonen Jukka (Tike)]

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 €) 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

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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