[OSM-talk] OT: making heat maps and overlaying on OSM data

Tom Chance tom at acrewoods.net
Fri Feb 27 10:55:45 GMT 2009


On Thu, 26 Feb 2009 18:19:53 -0500 (EST), simon at mungewell.org wrote:
>> Can anyone give me any tips on how to take a simple table of data with a
>> figure
>> for each coordinate, and turn it into a heat map? At first I thought of
>> GeoCommons but it seems you can only use pre-processed data with their
>> Maker
>> tool.
> 
> It sounds like you don't want to do any pre-processing... if you change
> your mind you could:
> 
> 1). Create a coloured overlay and place that as a translucent layer.
> http://openlayers.org/dev/examples/layer-opacity.html
> 
> This could be a single image file, or another tile server (as per
example).
> 
> 2). Create a set of vector shapes (contours?) and overlay those using an
> OSM or other layer (could be heavy on browser if a larger area).
> 
> The Srtm2Osm scripts already make the contours so these can probably be
> abused.
> 
> 
> Other hint: applications like Gnuplot and matlab can take single point
> data and export a x-by-y table of data. In gnuplot use the 'set term
> table' command a replot your graph

Thanks for the tips. Maybe one day I'll look into all of that but what I'm
really hoping for is something like this:

http://www.heatmapapi.com/

But that allows me to use OpenLayers. I've got a simple example of the heat
map bit with OSM tiles here:

http://www.bioregional.com/heatmap.html

We have a table of businesses with lonlat and a CO2 emissions quantity, I
want to overlay coloured markers for each point and a heatmap layer to give
the overall impression (as with that Google-based API). I also want to be
able to produce high quality images for a printed report, i.e. not just
screenshots of a Google map if possible.

My problem is that I haven't got time to work out (in my technically
deficient way) how to turn a 2 column table into something that I can put
through gnuplot or srtm2osm and eventually get into an OpenLayers overlay.
So at the moment I'll probably have to opt for the google API.

Regards,
Tom




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