How we measure

Two open sources sit under every page. OpenSkiMap compiles every ski area, lift and run from OpenStreetMap and adds elevations. OpenStreetMap itself gives us the lodging, shops, trailheads, bike trails and lakes. Brand hotels it hasn't mapped yet come from Overture Maps, a second open places file, and only when the chain has a page for that exact hotel; where both list a hotel, the map's entry is kept. Condos and rental homes are the big gap: no open source lists them well, so every count here is a floor, not a total.

• Where the lift starts. For each chairlift, gondola, aerial tram or funicular we take the end of the lift line that sits lower. Surface lifts, rope tows and carpets are left out of the walk.
• Which lift. The nearest lift bottom you can walk to: one near the lowest lift on the mountain, at the main base, or with lodging beside it. A chair that starts halfway up the hill is never the target.
• Walking minutes. A walking route along the map's streets and paths, from the building to the bottom station, walked at an easy 3 mph. We tested a shortcut (straight line plus a quarter) against real routes before launch and it came out too short in mountain villages, so we dropped it: no route, no minutes.
• No route on the map. We give the distance as the crow flies, in miles. A place within about 650 feet of a lift whose path the map is missing shows its distance in feet.
• A route that makes no sense. When the route comes out more than four times the straight line, the map is sending walkers the long way round a gap in its paths. We do not print those minutes; you get the distance.
• Too far to walk. Distance in miles as the crow flies. Roads wind, so the drive is longer.
• Summer. A lift counts as carrying bikes when its map entry says so. Trailheads, bike trails, coasters and lakes are the map's own entries.
• Near each place. The closest named place to eat, grocery store and pharmacy within about 0.4 miles of the building itself, as the crow flies.
• Mountain facts. Lift and run counts and elevations come from OpenSkiMap's statistics for that ski area.

Limits

A route on the map is not a cleared sidewalk in January, so every page says "about". The map can be out of date: a new lift, a closed hotel or a renamed trail takes time to reach it. What a building calls itself (hotel, condo, chalet) is the map's label. We never inspect rooms and never rate a place.

The map is read again every month. Spot something wrong? Write to us. A correction made on OpenStreetMap itself helps every app that draws on it.