Route Des Alpes
2168.0 m · net rise 148.3 m · total ascent 165.4 m · overall 6.8% · evidence quality U (needs confirmation) · Gwaelod-y-garth · South Glamorgan · share
Shape: stepped — 50% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 110 m.
Documented on the ground — sign: 16% (2026). Signs get repainted and tags get retagged, so the date is part of the fact; not yet matched against any cycling list.
needs review short window divergence — treat short-window maxima here as provisional.
≈ Overhead cover (tree canopy or structures) spans 55% 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) | ≈49% | 359–361 m | under overhead cover terrain reads 68.6% at 206–208 m across a structure — excluded |
| 3 m (diagnostic) | ≈38% | 358–361 m | under overhead cover terrain reads 58.9% at 205–208 m across a structure — excluded |
| 5 m | ≈34% | 132–137 m | under overhead cover terrain reads 51.5% at 204–209 m across a structure — excluded |
| 10 m | ≈25% | 277–287 m | under overhead cover terrain reads 37.3% at 199–209 m across a structure — excluded |
| 20 m | ≈22.1% | 5–25 m | under overhead cover terrain reads 30.7% at 92–112 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 25 m | ≈21.9% | 1–26 m | under overhead cover terrain reads 30.6% at 88–113 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 50 m | ≈17.2% | 152–202 m | under overhead cover terrain reads 24.4% at 266–316 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 100 m | ≈12.9% | 348–448 m | under overhead cover terrain reads 18.6% at 261–361 m across a structure — excluded |
may start earlier 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
No aerial layer here: Britain has no open or government source of aerial photography at road scale — the pan-government APGB imagery is licensed to the public sector only, unlike the LiDAR this survey is measured from. Street View, where it exists, is the visual check.
This climb's data: OCL JSON — the full gradient ladder, quality flags and provenance in the OpenClimb Ladder format.
Access: Held for re-survey — re-line 2026-09-02 refused, snapped to OS Open Roads but the maximum window still sits beside the road (Peter's class verdict D4). Also held 2026-09-14 (driveway-at-window, UK chips sweep): the steepest 25 m (21.9 %, at 1 m) runs along OSM service (driveway) way 329290218, 0.0 m from the window, and the window sits 15.0 m off the inventory line — the maximum may be the driveway, not the road. Out of the rankings until a person rules.
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
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).
Reported values vs. measurement
| Source | Claim | Evidence | Best-matching window |
|---|---|---|---|
| Road sign (16%, Gwaelod-y-garth foot) | 16% | road_sign | 50 m (-1.2 pp) |
Measurement card
| Elevation | Welsh Government — Welsh Government LiDAR 1m DTM (2020-2023) |
|---|---|
| Resolution / CRS | 1.0 m grid, EPSG:27700; sampled every 1.0 m, bilinear interpolation |
| Tiles | wg_del_2_309183_20201125dtm.tif, wg_del_2_309184_20201125dtm.tif, wg_del_3_309182_20201125dtm.tif, wg_del_3_310182_20201125dtm.tif, wg_del_3_310183_20201125dtm.tif, wg_del_3_310184_20201125dtm.tif, wg_del_3_311182_20201125dtm.tif, wg_del_3_311183_20201125dtm.tif, wg_del_3_311184_20201125dtm.tif |
| Road centreline | OpenStreetMap (local PBF extract) |
| Quality status | evidence quality U; review flags: short window divergence |
| Analysis | OCL 0.1.0, analysis 0.1.0, run texture-uk-wales-260912, calculated 2026-09-12 |
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:27700",
"elevation_resolution_m": 1.0,
"elevation_tiles": [
"data/cache/wales/dtm_1m/wg_del_2_309183_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_2_309184_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_3_309182_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_3_310182_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_3_310183_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_3_310184_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_3_311182_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_3_311183_20201125dtm.tif",
"data/cache/wales/dtm_1m/wg_del_3_311184_20201125dtm.tif"
],
"calculated_at": "2026-09-12T01:42:38+00:00",
"road_source": "OpenStreetMap (local PBF extract)",
"road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
"osm_pbf_path": "output/texture-uk-wales/batch-england-rchunk00.pbf",
"osm_snapshot": "",
"run_id": "texture-uk-wales-260912",
"elevation_provider": "Welsh Government",
"elevation_dataset": "Welsh Government LiDAR 1m DTM (2020-2023)",
"elevation_licence": "Open Government Licence v3 \u2014 \u00a9 Crown copyright Welsh Government",
"elevation_catalogue_layer": "geonode:welsh_government_lidar_tile_catalogue_2020_2023",
"elevation_tile_ids": [
"wg_del_2_309183_20201125dtm.tif",
"wg_del_2_309184_20201125dtm.tif",
"wg_del_3_309182_20201125dtm.tif",
"wg_del_3_310182_20201125dtm.tif",
"wg_del_3_310183_20201125dtm.tif",
"wg_del_3_310184_20201125dtm.tif",
"wg_del_3_311182_20201125dtm.tif",
"wg_del_3_311183_20201125dtm.tif",
"wg_del_3_311184_20201125dtm.tif"
],
"elevation_capture_dates": [
"26-11-2020"
],
"climb_origin": "discovered",
"license": "ODbL-1.0",
"license_url": "https://howsteep.org/licensing"
}