I'm wondering if anyone can point me to resources for making a heatmap entirely within PostGIS. I'm able to create a new raster with an empty band, but it's not clear to me how I can assign values based on the density of nearby vector features.
asked Oct 13, 2016 at 19:16
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1I think this is you are looking for: trac.osgeo.org/postgis/ticket/2894– Jean-Paul KasprzykCommented Apr 29, 2017 at 1:05
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1 Answer
The only way I've thought about truly doing a heatmap and/or density map in PostGIS is to break down what density is really doing:
- Create a grid of X cell size - this could be a vector dataset, rather than raster, and there are methods of doing this elsewhere on this forum
- Determine the radius you want to look for points around each cell
- For each cell, get the count of points within the radius around the cell using ST_DWithin
- Your output is then the number of points per unit of the area of the radius you are searching
That's essentially what density is doing - different methods such as Kernel density are a bit more in depth, but maybe someone else can lend a more refined explanation of density as it relates to breaking it down into a problem like this...
While I haven't done this YET - this is something I've been meaning to try for a while, but have so far been successful using the QGIS Heatmap plugin and/or the QGIS Heatmap layer style - SO - if you want to try this out, we can refine this answer together...
answered Oct 13, 2016 at 21:00
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1I had thought along those lines as well. From the documentation it looks like that's the workflow that PostGIS envisions--creating a vector representation of the cell and then doing whatever spatial operation needs to be done. Commented Oct 14, 2016 at 18:59