Paved · ranked
4652.4 m · net rise 326.2 m · total ascent 346.7 m · overall 7.0% · evidence quality B (good) · Sospel · Alpes-Maritimes
Shape: stepped — 46% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 98 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.
D2566a (Sospel, Alpes-Maritimes) is 4652.4 m long at 7.0% overall; its steepest 25 m averages ≈9.6% and its steepest 100 m ≈9.3%, measured from IGN's LiDAR HD 0.5 m laser surveys along the mapped road centreline.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | ≈19% | 693–695 m | under overhead cover terrain reads 404.3% at 4288–4290 m across a structure — excluded |
| 3 m (diagnostic) | ≈15% | 661–664 m | under overhead cover terrain reads 322.4% at 4288–4291 m across a structure — excluded |
| 5 m | ≈11% | 659–664 m | under overhead cover terrain reads 214.9% at 4287–4292 m across a structure — excluded |
| 10 m | ≈10% | 2009–2019 m | under overhead cover terrain reads 176.6% at 4283–4293 m across a structure — excluded |
| 20 m | ≈9.8% | 2004–2024 m | under overhead cover terrain reads 104.6% at 4283–4303 m across a structure — excluded |
| 25 m | ≈9.6% | 1999–2024 m | under overhead cover terrain reads 92.3% at 4283–4308 m across a structure — excluded |
| 50 m | ≈9.4% | 1997–2047 m | under overhead cover terrain reads 68.4% at 4283–4333 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.
One-way street: traffic runs downhill here, so the ascent is against the traffic flow for 38 m of this route (OpenStreetMap oneway tag). Published and ranked as measured — riding against a one-way may be restricted or illegal locally; check signage.
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%
Route line = the road surface as the LiDAR survey finds it. Basemap roads are for orientation and may sit a few metres off.
© 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 B; review flags: max5 over 45, short window divergence |
| Analysis | OCL 0.1.0, analysis 0.1.0, run remeasure-260929c-fr, calculated 2026-09-29 |
Provenance
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"remeasured": {
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"why": "block-extract cache sweep: fold the fallers, risers held published (standing rulings)",
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"license_url": "https://howsteep.org/licensing"
}