#30DayMapChallenge 2026 · 1–30 November

Heat & Housing30 maps of German cities

One interactive map a day on urban heat, housing and land in Germany's eight largest cities, built only from open data. Every map is a small web app with its own data pipeline, method notes and downloads.

By Barış Parlatangiller, GIS analyst & geospatial data engineer, Frankfurt am Main · GitHub · 30daymapchallenge.com

Maps per city · click a city to filter

How the maps are made

Each day lives in its own public GitHub repository. A GitHub Action downloads or reads the open data, runs the analysis in Python, builds the web data and publishes the map with GitHub Pages. Maps run on MapLibre GL; methods, limits and sources are written up on every page.

Data & honesty

Only open data: Zensus 2022, official land values (BORIS), LoD2 buildings, tree registers, Landsat, OpenStreetMap and more, each credited on its map. Scenarios are labelled as what-ifs, not forecasts. The maps were built with AI assistance (Claude, Anthropic); the questions, choices and checks are mine.