Thanks for the info Jim. Indeed that was my first inclination as well but once I thought about it I started to struggle with how I could fit it into the vector pipeline cleanly. HeatmapProcess didn’t seem to really apply since the aggregation needs to be done on the Solr side and not by the rendering transform. Is that how the GeoMesa heatmaps work?
To make that approach I would need to hack the request to include all the required facet parameters. I couldn’t really think of a clean way to do that although thinking about it again I could probably just throw a bunch of hints into the query that would trigger the Solr datastore to engage all of the facetting stuff… I think i’ll explore that approach as well, thanks Jim! My other thought was that the heatmap coverage could be useful for reasons other than purely visualizing areas of density. Like for instance using it as a mask against another coverage to do some processing… I don’t have a concrete use case there but thought it had potential. On Wed, Apr 6, 2016 at 2:14 PM Jim Hughes <[email protected]> wrote: > Hi Justin, > > Since it is somewhat similar, I wanted to share how GeoMesa creates > heatmaps using GeoServer. We have a small WPS which riffs on the > HeatMapProcess (1). That process is called via an SLD. By doing that, we > can have a regular vector layer, but then generate heatmaps for it without > fiddling with a second coverage, etc. > > Potentially, an approach like that could line up more of the rendering > pipeline to achieve blur, etc. > > Cheers, > > Jim > > 1. > https://github.com/geotools/geotools/blob/master/modules/unsupported/process-feature/src/main/java/org/geotools/process/vector/HeatmapProcess.java > > > On 04/06/2016 04:02 PM, Justin Deoliveira wrote: > > Hi folks, > > I’m working on a project to expose Solr’s heatmap capability through > GeoServer. You can find details about Solr heatmaps here: > > https://cwiki.apache.org/confluence/display/solr/Spatial+Search (search > for “Heatmap Faceting”. > > But the gist of it is this: If you have a spatial field that uses the > recursive prefix tree type (ie. geohash) for indexing then it’s easy using > Solr’s facetting infrastructure to generate a heatmap grid. What you get > back from Solr is a 2D array representing the geohash grid, where each > value is a count of documents that intersect that grid cell. Applying some > symbolization you can get something that looks like this: > > > https://raw.githubusercontent.com/voyagersearch/leaflet-solr-heatmap/master/sample.png > > The above screen shot comes from a leaflet plugin that visualizes the > heatmap directly in the browser. I would like to add a similar looking > visualization for GeoTools/GeoServer. > > My first thought was to expose this as a new type of coverage reader, > since the data is simple grid it falls into the model quite easily. The > major benefit of this approach is that becomes trivial to configure in > GeoServer and easy to style using all of the existing raster symbology > support. I’m interested to hear if others think this is a good approach. > > If that sounds good my plan was to add this to the existing solr module. > It won’t add any new dependencies aside from a dependency on the coverage > module. > > @Andrea: you’re listed as the module maintainer… although if I recall > correctly we agreed to co-maintain the module? > > I have a prototype working so if that all sounds good I’ll push up a > branch for folks to look at. One thing I am particular eager to get some > feed back on is how to best achieve the blur affect that makes heatmaps > look “ > pretty”. At the moment what I have done is baked in a parameter to the > coverage format that specifies a blur radius and then when reading the > coverage I run it through the Convolve operation to achieve the desired > affect. It would be ideal if this could be done at symbolization time. I’m > wondering if we currently have any way to define a blur or some similar > effect at rendering time with sld? Would a rendering transform work? > > Thanks folks. > > -Justin > > > > ------------------------------------------------------------------------------ > > > > _______________________________________________ > GeoTools-Devel mailing > [email protected]https://lists.sourceforge.net/lists/listinfo/geotools-devel > > > > ------------------------------------------------------------------------------ > _______________________________________________ > GeoTools-Devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/geotools-devel >
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