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Method

Sealed soil around the point

In short

ISPRA publishes the national soil consumption map as a raster of 10 metre pixels: each pixel carries one class of its legend, from "2 - Suolo non consumato" to "111 - Edifici, fabbricati". The pixel an address falls on almost always says "buildings", which is true and of little use. This method counts the pixels around the point instead: how much of the soil within 100 metres, and within 500 metres, the map classifies as artificial cover. It is a share computed by TerraOverview from the source data, not a number ISPRA publishes for that point.

The steps

  1. The confirmed point, in geographic coordinates, is converted into the map’s own system (RDN2008 / Italy zone, EPSG:7794) with the same formula GDAL uses; compared on fifty points across Italy the difference is under a tenth of a millimetre.
  2. The pixels whose centre falls within the radius of the point are taken: 314 pixels for the 100 metre circle, about 7,850 for the 500 metre one.
  3. The numerator is the pixels of artificial cover, that is the 1xx classes of the legend: both permanent consumption (buildings, paved roads, railways, yards, landfills) and reversible consumption (building sites, unpaved roads, quarries not restored, ground-mounted photovoltaics). The distinction between permanent and reversible is ISPRA’s, and their sum is what ISPRA calls «suolo consumato».
  4. The denominator counts only the pixels the map covers. At sea and outside the national territory the map has no data, and counting those as open soil would make a house on the coast look greener than it is.
  5. Beside the two shares the report prints the class of the pixel the point falls on, in the words of the ISPRA legend, and the number of pixels counted, so the arithmetic can be redone.

What this number is not

  • There is no threshold beyond which a share becomes "high": ISPRA publishes none, and TerraOverview invents none. The value is a context measurement, not a flag.
  • The map is photo-interpreted on 10 metre pixels and updated once a year: a yard, a canopy or a recent building site can fall in the neighbouring pixel or not be there yet.
  • The share says nothing about who owns that soil or what may be built on it: it is not a planning datum, and what may be built is for the municipality to say.
  • Consumed soil is not a synonym for sealed: ISPRA distinguishes permanent from reversible artificial cover, and this count adds them, as the source does.

Where the code is

  • pipeline/python/build_soil_blocks.py
  • packages/geo/src/soil-blocks.ts
  • packages/geo/src/italy-zone.ts
  • packages/sources/src/adapters/ispra-consumo-suolo.ts