Col du Mont Cenis from Lanslebourg-Mont-Cenis
9864.7 m · net rise 684.8 m · total ascent 703.1 m · overall 6.9% · evidence quality B (good) · Val-Cenis · Savoie · share
Shape: sustained — 29% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 35 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) | ≈26% | 3206–3208 m | under overhead cover terrain reads 284.8% at 904–906 m across a structure — excluded |
| 3 m (diagnostic) | ≈22% | 3206–3209 m | under overhead cover terrain reads 261.7% at 903–906 m across a structure — excluded |
| 5 m | ≈16% | 3204–3209 m | under overhead cover terrain reads 165.0% at 903–908 m across a structure — excluded |
| 10 m | ≈11% | 3199–3209 m | under overhead cover terrain reads 84.5% at 903–913 m across a structure — excluded |
| 20 m | ≈10.8% | 3189–3209 m | under overhead cover terrain reads 51.1% at 36–56 m across a structure — excluded |
| 25 m | ≈10.4% | 6586–6611 m | under overhead cover terrain reads 41.9% at 35–60 m across a structure — excluded |
| 50 m | ≈10.1% | 6566–6616 m | under overhead cover terrain reads 22.9% at 35–85 m across a structure — excluded |
| 100 m | ≈9.4% | 6540–6640 m | under overhead cover terrain reads 14.7% at 35–135 m across a structure — excluded |
descends at start 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%
© OpenStreetMap contributors · topo tiles © OpenTopoMap (CC-BY-SA) · vector tiles OpenFreeMap · aerial imagery © IGN, BD ORTHO® (Licence Ouverte Etalab 2.0)
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 | E1004-N6472, E1005-N6469, E1005-N6470, E1005-N6471, E1005-N6472, E1006-N6469, E1006-N6470, E1006-N6471, E1006-N6472 |
| Road centreline | OpenStreetMap (local PBF extract) |
| Quality status | evidence quality B; caveated windows: canopy or structure, structure excluded, texture excluded |
| Analysis | OCL 0.1.0, analysis 0.1.0, run fr-alps4, calculated 2026-09-17 |
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:2154",
"elevation_resolution_m": 0.5,
"elevation_tiles": [
"data/cache/fr/ign-lidarhd_dtm_E1004-N6472_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1005-N6469_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1005-N6470_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1005-N6471_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1005-N6472_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1006-N6469_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1006-N6470_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1006-N6471_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1006-N6472_0m5.tif"
],
"calculated_at": "2026-09-17T02:10:03+00:00",
"road_source": "OpenStreetMap (local PBF extract)",
"road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
"osm_pbf_path": "data/cache/pbf/block-batch-fr-alps4.osm.pbf",
"osm_snapshot": "",
"run_id": "fr-alps4",
"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": [
"E1004-N6472",
"E1005-N6469",
"E1005-N6470",
"E1005-N6471",
"E1005-N6472",
"E1006-N6469",
"E1006-N6470",
"E1006-N6471",
"E1006-N6472"
],
"elevation_blocks": [
"21LHD6RM@2025-06-06"
],
"ign_dalles": [
"LHD_FXX_1004_6473_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1005_6470_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1005_6471_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1005_6472_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1005_6473_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1006_6470_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1006_6471_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1006_6472_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1006_6473_MNT_O_0M50_LAMB93_IGN69"
],
"ign_missions": [
"21LHD6RM"
],
"ign_editions": [
"2025-06-06"
],
"ign_dsm_edition": {
"LHD_FXX_1004_6473_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1005_6470_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1005_6471_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1005_6472_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1005_6473_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1006_6470_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1006_6471_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1006_6472_MNT_O_0M50_LAMB93_IGN69": "2025-06-06",
"LHD_FXX_1006_6473_MNT_O_0M50_LAMB93_IGN69": "2025-06-06"
},
"climb_origin": "named-pass",
"structure_own_ways": "none \u2014 the route carried no way list; own decks unmasked",
"carriageway": {
"stations": 401,
"stations_resolved": 401,
"width_median_m": 9.25,
"width_p10_m": 7.5,
"width_min_m": 1.0,
"width_max_m": 12.0,
"bounded_share": 0.04,
"unbounded_share": 0.96,
"confidence_median": 0.0,
"width_median_bounded_m": 9.25,
"window_m": [
6586.0,
6611.0
],
"width_at_max25_m": 9.25,
"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": 401,
"stations_resolved": 401,
"width_median_m": 11.5,
"width_p10_m": 5.25,
"width_min_m": 0.5,
"width_max_m": 12.0,
"bounded_share": 0.262,
"unbounded_share": 0.738,
"confidence_median": 0.0,
"width_median_bounded_m": 6.75,
"window_m": [
6586.0,
6611.0
],
"width_at_max25_m": 12.0,
"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"
}