Col de Castillon from Sospel
4653.0 m · net rise 326.2 m · total ascent 346.8 m · overall 7.0% · evidence quality U (needs confirmation) · Sospel · Alpes-Maritimes · share
Shape: stepped — 46% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 74 m.
Not yet matched against documented climbs — the measurement stands on its own.
needs review max5 over 45, short window divergence — treat short-window maxima here as provisional.
≈ Overhead cover (tree canopy or structures) spans 9% of this route — detected by comparing the surface model (DSM, treetops and rooftops) against the terrain model (DTM, bare ground). Under cover the bare-ground model is built from fewer laser returns, so metre-scale readings can wobble; maxima whose window sits in a covered zone are marked ≈ below — less certain — the flag does not say whether the true value is higher or lower. Longer windows average over more clean ground and are steadier.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | ≈52% | 4537–4539 m | under overhead cover terrain reads 366.7% at 4289–4291 m across a structure — excluded |
| 3 m (diagnostic) | ≈47% | 4537–4540 m | under overhead cover terrain reads 310.6% at 4288–4291 m across a structure — excluded |
| 5 m | ≈46% | 4537–4542 m | under overhead cover terrain reads 215.2% at 4288–4293 m across a structure — excluded |
| 10 m | ≈14% | 4600–4610 m | under overhead cover terrain reads 174.6% at 4283–4293 m across a structure — excluded |
| 20 m | ≈9.8% | 2004–2024 m | under overhead cover terrain reads 104.2% at 4284–4304 m across a structure — excluded |
| 25 m | ≈9.6% | 2003–2028 m | under overhead cover terrain reads 92.1% at 4283–4308 m across a structure — excluded |
| 50 m | ≈9.4% | 1998–2048 m | under overhead cover terrain reads 68.3% at 4284–4334 m across a structure — excluded |
| 100 m | ≈9.3% | 1997–2097 m | under overhead cover terrain reads 45.4% at 4270–4370 m across a structure — excluded |
may 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 (0% unpaved), according to BD TOPO®, IGN's national topographic database: paved for the first 4,317 m; off the road model from 4,317 m to 4,447 m; paved from 4,447 m to the top.
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 | E1057-N6314, E1057-N6315, E1057-N6316, E1057-N6317, E1057-N6318, E1058-N6314, E1058-N6315 |
| Road centreline | OpenStreetMap (local PBF extract) |
| Quality status | evidence quality U; review flags: max5 over 45, short window divergence |
| 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_E1057-N6314_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1057-N6315_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1057-N6316_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1057-N6317_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1057-N6318_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1058-N6314_0m5.tif",
"data/cache/fr/ign-lidarhd_dtm_E1058-N6315_0m5.tif"
],
"calculated_at": "2026-09-17T02:18:08+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": [
"E1057-N6314",
"E1057-N6315",
"E1057-N6316",
"E1057-N6317",
"E1057-N6318",
"E1058-N6314",
"E1058-N6315"
],
"elevation_blocks": [
"21LHD8SP@2025-06-20"
],
"ign_dalles": [
"LHD_FXX_1057_6315_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1057_6316_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1057_6317_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1057_6318_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1057_6319_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1058_6315_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_1058_6316_MNT_O_0M50_LAMB93_IGN69"
],
"ign_missions": [
"21LHD8SP"
],
"ign_editions": [
"2025-06-20"
],
"ign_dsm_edition": {
"LHD_FXX_1057_6315_MNT_O_0M50_LAMB93_IGN69": "2025-06-20",
"LHD_FXX_1057_6316_MNT_O_0M50_LAMB93_IGN69": "2025-06-20",
"LHD_FXX_1057_6317_MNT_O_0M50_LAMB93_IGN69": "2025-06-20",
"LHD_FXX_1057_6318_MNT_O_0M50_LAMB93_IGN69": "2025-06-20",
"LHD_FXX_1057_6319_MNT_O_0M50_LAMB93_IGN69": "2025-06-20",
"LHD_FXX_1058_6315_MNT_O_0M50_LAMB93_IGN69": "2025-06-20",
"LHD_FXX_1058_6316_MNT_O_0M50_LAMB93_IGN69": "2025-06-20"
},
"climb_origin": "named-pass",
"structure_own_ways": "none \u2014 the route carried no way list; own decks unmasked",
"carriageway": {
"stations": 193,
"stations_resolved": 193,
"width_median_m": 8.0,
"width_p10_m": 5.05,
"width_min_m": 1.0,
"width_max_m": 11.5,
"bounded_share": 0.238,
"unbounded_share": 0.762,
"confidence_median": 0.0,
"width_median_bounded_m": 7.75,
"window_m": [
2003.0,
2028.0
],
"width_at_max25_m": 8.75,
"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": 193,
"stations_resolved": 193,
"width_median_m": 8.75,
"width_p10_m": 3.55,
"width_min_m": 0.5,
"width_max_m": 12.0,
"bounded_share": 0.549,
"unbounded_share": 0.451,
"confidence_median": 1.0,
"width_median_bounded_m": 7.38,
"window_m": [
2003.0,
2028.0
],
"width_at_max25_m": 11.75,
"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"
}