LIVING SURVEY — measurements are reviewed continuously as new data and local evidence arrive. Seen a sign, a gate, or a better name? Submit an update no account needed · photos welcome via GitHub

Route du Gros-Mont

2446.6 m · net rise 310.3 m · total ascent 319.7 m · overall 12.7% · evidence quality B (good) · Val-de-Charmey · Fribourg/Freiburg · share

Shape: sustained — 29% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 364 m.

Found purely from mapping and LiDAR data, and not yet matched against books, race records or lists — it may be well known to locals under a name we've never heard. It was cross-checked against swisstopo’s swissTLM3D road model, OpenStreetMap and a second terrain model, but a discovery can still be an artifact of the terrain model or the map. Treat it as a well-evidenced hypothesis until someone has ridden it. If you know this road, tell us what you found — photographs, corrections and local knowledge all welcome; the map links below let you scout it first.

Gradient ladder what do windows mean?

Window	Maximum	Located at
2 m (diagnostic)	≈40%	853–855 m	under overhead cover terrain reads 148.8% at 2404–2406 m across a structure — excluded
3 m (diagnostic)	≈33%	853–856 m	under overhead cover terrain reads 141.1% at 2403–2406 m across a structure — excluded
5 m	≈23%	853–858 m	under overhead cover terrain reads 102.2% at 2402–2407 m across a structure — excluded
10 m	≈20%	2367–2377 m	under overhead cover terrain reads 59.2% at 2400–2410 m across a structure — excluded
20 m	≈19.8%	2357–2377 m	under overhead cover terrain reads 37.2% at 2400–2420 m across a structure — excluded
25 m	≈19.7%	2352–2377 m	under overhead cover terrain reads 32.7% at 2400–2425 m across a structure — excluded
50 m	≈18.9%	2327–2377 m	under overhead cover terrain reads 19.8% at 2396–2446 m across a structure — excluded
100 m	17.0%	953–1053 m

descends at startmay continue beyond end Extent detection suggests reviewing where this climb starts/ends.

Map

Check this route yourself: Google Maps route via their router · Street View at the base where coverage exists · geojson.io our exact measured line · OpenTopoMap

This climb's data: OCL JSON — the full gradient ladder, quality flags and provenance in the OpenClimb Ladder format.

Surface: paved throughout, according to swisstopo's swissTLM3D road model.

Measured, not vetted. This page records what the laser record shows about the road's shape — nothing more. Nobody has necessarily ridden or inspected this road for the survey, and a page here is not a recommendation and no guarantee that the road is open, surfaced, rideable or safe. Gates, private sections, missing rights of way and hazards do not show up in elevation data. Check access and conditions on the ground and make your own judgment.

Ridden it, or know better? Submit data for this climb no account needed · Share this climb

Route colour = gradient over a 25 m window: <10% 10–20% 20–25% ≥25%

Route du Gros-Mont LiDAR hillshade map with contours

Profile

The map, profile and gradient chart share one position — move your pointer over them and the marker follows. Colors are the gradient bands; the shaded span is the steepest 25 m. Any 25 m figure is good to about a point either way (why).

Measurement card

Elevation	swisstopo swissALTI3D — swissALTI3D 0.5 m DTM (Federal Office of Topography swisstopo)
Resolution / CRS	0.5 m grid, EPSG:2056; sampled every 1.0 m, bilinear interpolation
Tiles	2581-1156, 2581-1157
Road centreline	OpenStreetMap (local PBF extract)
Quality status	evidence quality B; caveated windows: structure excluded
Analysis	OCL 0.1.0, analysis 0.1.0, run ch-run6-260910, calculated 2026-09-10

Provenance

{
  "analysis_version": "0.1.0",
  "sample_interval_m": 1.0,
  "interpolation": "bilinear",
  "smoothing": "none",
  "gradient_windows_m": [
    5.0,
    10.0,
    20.0,
    25.0,
    50.0,
    100.0
  ],
  "diagnostic_windows_m": [
    2.0,
    3.0
  ],
  "elevation_crs": "EPSG:2056",
  "elevation_resolution_m": 0.5,
  "elevation_tiles": [
    "data/cache/ch/swissalti3d_2021_2581-1156_0.5_2056_5728.tif",
    "data/cache/ch/swissalti3d_2021_2581-1157_0.5_2056_5728.tif"
  ],
  "calculated_at": "2026-09-10T20:40:54+00:00",
  "road_source": "OpenStreetMap (local PBF extract)",
  "road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
  "osm_pbf_path": "data/cache/pbf/switzerland-2026-09-10-batch.osm.pbf",
  "osm_snapshot": "",
  "run_id": "ch-run6-260910",
  "elevation_provider": "swisstopo swissALTI3D",
  "elevation_licence": "swisstopo open government data (OGD): free use, attribution '\u00a9 swisstopo' \u2014 https://www.swisstopo.admin.ch/en/terms-and-conditions",
  "elevation_dataset": "swissALTI3D 0.5 m DTM (Federal Office of Topography swisstopo)",
  "elevation_tile_ids": [
    "2581-1156",
    "2581-1157"
  ],
  "climb_origin": "discovered",
  "canopy_check": "unavailable \u2014 no surface model (DSM or point cloud) registered for this coverage",
  "mask_basin_extension_m": 30.0,
  "license": "ODbL-1.0",
  "license_url": "https://howsteep.org/licensing"
}