Where the numbers come from.

Every time “from Milan” starts from a single point: Piazza del Duomo, 45.464° N · 9.191° E (OpenStreetMap, via Nominatim). The second reference is Malpensa Terminal 1, 45.627° N · 8.711° E, the railway station beneath the terminal.

Arrivals are the village point in OpenStreetMap: the main village node for municipalities, the hamlet node for Legro, Ronco and Vacciago, the town hall for Madonna del Sasso. Every point carries its OSM identifier in the data.

For each source: what it measures, how we use it, the licence and the date.

• Driving times and distances

  measured on 6 October 2026

  OSRM, the open routing engine, on the public demo server; car profile, no traffic. 11 starting cities to 16 places, plus 10 comparison routes to the other lakes. These times are usually optimistic: they ignore queues (Milan ring roads, the A8 at rush hour), roadworks, Swiss border checks and stops.

  Data © OpenStreetMap contributors, ODbL 1.0 · project-osrm.org

• Place points

  extracted on 6 October 2026

  OpenStreetMap Nominatim, one request every 1.2–1.3 seconds; points checked against the “place” nodes of the same extract.

  © OpenStreetMap contributors, ODbL 1.0 · openstreetmap.org/copyright

• Ground elevation

  extracted on 6 October 2026

  The point elevation comes from Copernicus DEM GLO-90 (about 90 m) via Open-Meteo; minimum, median and maximum within 400 m from AWS Terrain Tiles (EU-DEM and SRTM, zoom 12, about 27 m per pixel). It is ground elevation, not buildings. The two sources differ by 0–13 m across the 16 points.

  Copernicus DEM © DLR and/or Airbus, free use with attribution; Open-Meteo CC BY 4.0; Terrain Tiles: Copernicus, NASA, Mapzen · registry.opendata.aws/terrain-tiles

• Relief and contour lines

  extracted on 6 October 2026

  A 181 × 181 elevation grid over 45.70–45.95° N, 8.25–8.55° E, from Terrain Tiles; 100 m contours computed by us. 30–90 m models smooth the summits: the top of the Mottarone comes out about 25 m lower than it is.

  Copernicus (EU-DEM), NASA (SRTM), Mapzen · registry.opendata.aws/terrain-tiles

• Winter sun

  calculated on 6 October 2026

  Our own calculation: each place's horizon from the relief, every 2° of direction up to 15 km, with curvature and refraction; sun position from the NOAA formulas. Minutes of direct sun on 21 December. No buildings, trees or clouds: it is the most the terrain allows.

  Calculation by TriesteVillas srl on the relief data

• OMI property quotations

  extracted on 6 October 2026

  The Italian Revenue Agency's quotation database, public consultation service: 13 municipalities, all zones, residential use, second half of 2025 (the latest published) and second half of 2024. These are not sale prices: they are min–max ranges in €/m² of gross area, estimated per zone, type and prevailing condition.

  CC BY 4.0, “Agenzia delle Entrate – OMI” · agenziaentrate.gov.it · OMI

• Sales (NTN)

  extracted on 6 October 2026

  Residential sales volumes by province (Novara and Verbano-Cusio-Ossola), capital and rest of the province; 2025 and the first half of 2026 are provisional. Municipal detail requires the reserved area with a digital identity: we did not download it, because we use nobody's credentials.

  CC BY 4.0, “Agenzia delle Entrate – OMI” · agenziaentrate.gov.it · volumi di compravendita

• Population

  extracted on 6 October 2026

  ISTAT, resident population on 1 January 2025 by municipality (the 1 January 2026 estimate is context only).

  CC BY 4.0, ISTAT · demo.istat.it

• Schools

  extracted on 6 October 2026

  Italian Ministry of Education and Merit, register of state schools, school year 2026/27. State schools only: private accredited schools are not included.

  IODL 2.0 · dati.istruzione.it/opendata

• Landslides and floods

  extracted on 6 October 2026

  ISPRA, IdroGEO platform: share of population and municipal area in high or very high landslide hazard zones and medium flood hazard zones. These are values for the whole municipality: they say nothing about a specific house.

  CC BY 4.0, ISPRA · idrogeo.isprambiente.it

• Bathing water

  consulted on 6 October 2026

  European Environment Agency: 16 bathing points on the lake, class per season up to 2024, the latest available. Each point's municipality is inferred from the code in its identifier, not checked one by one.

  Public EEA data; the licence of the single table is not verified · discodata.eea.europa.eu

• The lake: measurements and water status

  consulted on 6 October 2026

  Piedmont Region, Water Protection Plan, Lake Orta monograph (area, depth, catchment); ARPA Piemonte for ecological and chemical status. Where sources disagree, the site gives both values.

  Public documents, cited with their source · regione.piemonte.it · PTA, monografia L3

• Shore, roads, railway, boats

  extracted on 6 October 2026

  OpenStreetMap via Overpass: the lake polygon, main roads, railway, stations, landing stages, boat lines and hospitals on the maps.

  © OpenStreetMap contributors, ODbL 1.0 · openstreetmap.org/copyright

• TriesteVillas numbers

  measured on 5 October 2026

  The TriesteVillas CRM, read only, and the public catalogues of the group's sites. Counts made with a program and checked with a second method that must give the same result; excluding tests, duplicates and spam. They concern the group, almost all in Trieste, not the lake.

  TriesteVillas srl

Two UTF-8 tables, comma-separated, generated from the same data the site uses. If you reuse them, cite the source and the licence of the original data.

The OMI quotations are not among the open files: consult them at the source, on the Revenue Agency's service.

To cite the atlas, or one of its pages: