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

Col de Prat-de-Bouc from La Sagnette

3178.6 m · net rise 190.1 m · total ascent 200.8 m · overall 6.0% · evidence quality B (good) · Paulhac · Cantal · share

Shape: sustained — 30% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 14 m.

Not yet matched against documented climbs — the measurement stands on its own.

Gradient ladder what do windows mean?

Window	Maximum	Located at
2 m (diagnostic)	≈9%	275–277 m	under overhead cover terrain reads 468.0% at 715–717 m across a structure — excluded
3 m (diagnostic)	≈9%	275–278 m	under overhead cover terrain reads 318.0% at 714–717 m across a structure — excluded
5 m	≈9%	273–278 m	under overhead cover terrain reads 193.6% at 714–719 m across a structure — excluded
10 m	≈9%	271–281 m	under overhead cover terrain reads 100.2% at 714–724 m across a structure — excluded
20 m	≈8.3%	261–281 m	under overhead cover terrain reads 53.4% at 714–734 m across a structure — excluded
25 m	≈8.3%	253–278 m	under overhead cover terrain reads 44.0% at 714–739 m across a structure — excluded
50 m	≈8.0%	232–282 m	under overhead cover terrain reads 25.0% at 714–764 m across a structure — excluded
100 m	≈7.7%	188–288 m	under overhead cover terrain reads 15.6% at 714–814 m across a structure — excluded

descends at 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 BD TOPO®, IGN's national topographic database.

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%

Col de Prat-de-Bouc from La Sagnette 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	IGN LiDAR HD MNT 0.5 m — LiDAR HD — MNT (sol) et MNS (surface), 0,50 m (Institut national de l'information géographique et forestière), RGF93 / Lambert-93 EPSG:2154, altitudes IGN69
Resolution / CRS	0.5 m grid, EPSG:2154; sampled every 1.0 m, bilinear interpolation
Tiles	E683-N6438, E683-N6439, E684-N6438, E684-N6439, E685-N6437, E685-N6438, E686-N6437
Road centreline	OpenStreetMap (local PBF extract)
Quality status	evidence quality B; caveated windows: structure excluded, structure excluded min
Analysis	OCL 0.1.0, analysis 0.1.0, run fr-mc4, calculated 2026-09-22

Provenance

{
  "analysis_version": "0.1.0",
  "run_manifest": {
    "manifest_version": "1",
    "code_git_sha": "1cc9fdcd6556a02163cb21acb2293cad3067d2a1",
    "code_git_dirty": "false",
    "analysis_version": "0.1.0",
    "analysis_config_digest": "sha256:8c94015b54267da4",
    "python": "3.14.4",
    "numpy": "2.5.3",
    "rasterio": "1.5.1",
    "pyproj": "3.8.0",
    "laspy": "2.7.0",
    "shapely": "2.1.2",
    "pyosmium": "4.3.1",
    "libosmium": "2.23.1",
    "gdal": "3.12.4",
    "proj": "9.8.1",
    "run_id": "fr-mc4",
    "road_pbf": "block-batch-fr-mc4.osm.pbf",
    "region_key": "france",
    "crs": "EPSG:2154",
    "elevation_provider_key": "ign-lidarhd",
    "tile_index": "wms-grid",
    "authority": "bdtopo",
    "registry_pbf": "france-vosges-2026-09-16.osm.pbf",
    "tile_index_snapshot": "sha256:af4eae1f5df9e232"
  },
  "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:2154",
  "elevation_resolution_m": 0.5,
  "elevation_tiles": [
    "data/cache/fr/ign-lidarhd_dtm_E683-N6438_0m5@22LHD3KM-2025-09-17.tif",
    "data/cache/fr/ign-lidarhd_dtm_E683-N6439_0m5@22LHD3KM-2025-09-17.tif",
    "data/cache/fr/ign-lidarhd_dtm_E684-N6438_0m5@22LHD3KM-2025-09-17.tif",
    "data/cache/fr/ign-lidarhd_dtm_E684-N6439_0m5@22LHD3KM-2025-09-17.tif",
    "data/cache/fr/ign-lidarhd_dtm_E685-N6437_0m5@22LHD3KM-2025-09-17.tif",
    "data/cache/fr/ign-lidarhd_dtm_E685-N6438_0m5@22LHD3KM-2025-09-17.tif",
    "data/cache/fr/ign-lidarhd_dtm_E686-N6437_0m5@21LHD4LM-2025-06-26.tif"
  ],
  "calculated_at": "2026-09-22T18:05:33+00:00",
  "road_source": "OpenStreetMap (local PBF extract)",
  "road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
  "osm_pbf_path": "data/cache/pbf/block-batch-fr-mc4.osm.pbf",
  "osm_snapshot": "",
  "run_id": "fr-mc4",
  "elevation_provider": "IGN LiDAR HD MNT 0.5 m",
  "elevation_licence": "Licence Ouverte / Open Licence 2.0 (Etalab) \u2014 \u00a9 IGN, LiDAR HD (MNT/MNS), data.geopf.fr; reproduction autoris\u00e9e avec mention de la source et de la date",
  "elevation_dataset": "LiDAR HD \u2014 MNT (sol) et MNS (surface), 0,50 m (Institut national de l'information g\u00e9ographique et foresti\u00e8re), RGF93 / Lambert-93 EPSG:2154, altitudes IGN69",
  "elevation_vertical_datum": "IGN69",
  "elevation_tile_ids": [
    "E683-N6438",
    "E683-N6439",
    "E684-N6438",
    "E684-N6439",
    "E685-N6437",
    "E685-N6438",
    "E686-N6437"
  ],
  "elevation_blocks": [
    "21LHD4LM@2025-06-26",
    "22LHD3KM@2025-09-17"
  ],
  "ign_dalles": [
    "LHD_FXX_0683_6439_MNT_O_0M50_LAMB93_IGN69",
    "LHD_FXX_0683_6440_MNT_O_0M50_LAMB93_IGN69",
    "LHD_FXX_0684_6439_MNT_O_0M50_LAMB93_IGN69",
    "LHD_FXX_0684_6440_MNT_O_0M50_LAMB93_IGN69",
    "LHD_FXX_0685_6438_MNT_O_0M50_LAMB93_IGN69",
    "LHD_FXX_0685_6439_MNT_O_0M50_LAMB93_IGN69",
    "LHD_FXX_0686_6438_MNT_O_0M50_LAMB93_IGN69"
  ],
  "ign_missions": [
    "21LHD4LM",
    "22LHD3KM"
  ],
  "ign_editions": [
    "2025-06-26",
    "2025-09-17"
  ],
  "ign_dsm_edition": {
    "LHD_FXX_0683_6439_MNT_O_0M50_LAMB93_IGN69": "2025-09-17",
    "LHD_FXX_0683_6440_MNT_O_0M50_LAMB93_IGN69": "2025-09-17",
    "LHD_FXX_0684_6439_MNT_O_0M50_LAMB93_IGN69": "2025-09-17",
    "LHD_FXX_0684_6440_MNT_O_0M50_LAMB93_IGN69": "2025-09-17",
    "LHD_FXX_0685_6438_MNT_O_0M50_LAMB93_IGN69": "2025-09-17",
    "LHD_FXX_0685_6439_MNT_O_0M50_LAMB93_IGN69": "2025-09-17",
    "LHD_FXX_0686_6438_MNT_O_0M50_LAMB93_IGN69": "2025-06-26"
  },
  "climb_origin": "named-pass",
  "structure_own_ways": 2,
  "structure_mask_ranges_m": [
    [
      0.0,
      15.0
    ]
  ],
  "carriageway": {
    "stations": 134,
    "stations_resolved": 134,
    "width_median_m": 8.25,
    "width_p10_m": 6.0,
    "width_min_m": 3.25,
    "width_max_m": 12.0,
    "bounded_share": 0.157,
    "unbounded_share": 0.843,
    "confidence_median": 0.0,
    "width_median_bounded_m": 8.25,
    "window_m": [
      253.0,
      278.0
    ],
    "width_at_max25_m": 6.0,
    "window_stations": 7,
    "single_track": false,
    "single_track_rule": "PROVISIONAL (2026-09-15): width_p10_m <= 3.0 m with bounded_share >= 0.6; recorded, not a rule",
    "status": "ok",
    "source": "dtm",
    "station_m": 25.0,
    "window_station_m": 5.0,
    "halfwidth_m": 6.0,
    "step_m": 0.25,
    "level_tol_m": 0.12,
    "break_min_m": 0.3,
    "stations_failed": 0,
    "hedge_to_hedge": {
      "stations": 134,
      "stations_resolved": 134,
      "width_median_m": 11.0,
      "width_p10_m": 9.25,
      "width_min_m": 4.75,
      "width_max_m": 12.0,
      "bounded_share": 0.149,
      "unbounded_share": 0.851,
      "confidence_median": 0.0,
      "width_median_bounded_m": 9.38,
      "window_m": [
        253.0,
        278.0
      ],
      "width_at_max25_m": 7.5,
      "window_stations": 7,
      "status": "ok",
      "source": "dsm",
      "station_m": 25.0,
      "window_station_m": 5.0,
      "halfwidth_m": 6.0,
      "step_m": 0.25,
      "level_tol_m": 0.5,
      "break_min_m": 0.3,
      "stations_failed": 0
    }
  },
  "license": "ODbL-1.0",
  "license_url": "https://howsteep.org/licensing"
}