The data is the Global Human Settlement Layer population grid for 2025. This release was known to be less accurate for small areas, especially where there has been rapid change in population.
The bus stop, tram stop, and train/metro stop data is from Open Street Map from early 2023 and has errors. Many stops are missing, especially outside of Europe. Stops included rarely used or heritage service stops.
Here's how I make this site,I convert the GeoTIFF files from the GHSL into populations at points.
- I load these points into an SQLite database.
- I add a compound index (on latitude and longitude) to this SQLite database so that lookups are very fast.
- I create an API in C# ASP.NET running on an Azure Web App that does some geographical processing and queries the SQLite database to calculate the population within any distance of any location.
- I use this website to perform those queries and display the results.
The maximum radius is set to 50km, it would get slow above that. I set the minimum radius to 3km because otherwise some city-centre populations are likely to be very wrong and I can't be bothered fielding all the "your amateurish tool gives completely spurious information and you should be ashamed of yourself!" type comments that would generate.
Estimated population in Sepúlveda within circle of 5 kms in 2025: 565 people
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