Area Density Heat Map QGIS

Question

I would like to make a heat map of "building density" based on the area of the building footprints (I have them in a geojson as polygons) in relation to their "non-building" surroundings based on fixed grid (or alternative). So in other words put a grid over the map 100x100m and in each grid sector look at the area relatioship between the building footprint and the surrounding footprint. The more building the denser.

How would I best go about this? Are there better ways to do area based heatmaps? I have calculated centroids for each building and made heat maps with that but I need something based on area not topology.

Answer 1

One approach is to convert your polygons to binary raster and calculate the percent building cover within a moving (focal) window for each pixel. Here is how:

1. Convert the vector polygon building footprints to binary raster where building = 1, else 0.

   Raster > Conversion > Rasterize (Vector to Raster)

2. Run a moving window using some areal unit that is meaningful (e.g. 100m^2, acres, miles^2, etc.) with a mean statistic to calculate percent building cover per unit area.

   Processing Toolbox > GRASS > Raster > r.neighbors