Lane near Dolgarrog°
665.7 m · net rise 148.9 m · total ascent 149.6 m · overall 22.4% · confidence: good · Dolgarrog · Clwyd · share
Shape: sustained — 33% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 466 m.
Matches: BikeRadar, "7 of the steepest UK climbs, ranked" — Listed by BikeRadar as Afon Ddu, Conwy Valley — independent corroboration of the survey's machine-found UK-steepest (36.6% over 25 m); established-name candidate pending the identification-certain check.
° The name is provisional: this climb is not yet matched to a documented name, so it was named from nearby map places. There is no evidence of local usage — (auto-named from gazetteer; was discovered-street-53-1793-3-8400). Corrections welcome.
≈ Overhead cover (tree canopy or structures) spans 75% 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) | ≈46% | 147–149 m | under overhead cover terrain reads 66.3% at 452–454 m across a structure — excluded |
| 3 m (diagnostic) | ≈41% | 500–503 m | under overhead cover terrain reads 66.3% at 451–454 m across a structure — excluded |
| 5 m | ≈40% | 499–504 m | under overhead cover terrain reads 56.3% at 451–456 m across a structure — excluded |
| 10 m | ≈39% | 494–504 m | under overhead cover terrain reads 44.0% at 445–455 m across a structure — excluded |
| 20 m | ≈37.0% | 484–504 m | under overhead cover terrain reads 38.1% at 440–460 m across a structure — excluded |
| 25 m | ≈36.6% | 479–504 m | under overhead cover terrain reads 36.7% at 440–465 m across a structure — excluded |
| 50 m | ≈34.7% | 458–508 m | under overhead cover terrain reads 36.3% at 451–501 m across a structure — excluded |
| 100 m | ≈27.4% | 458–558 m | under overhead cover terrain reads 32.2% at 421–521 m across a structure — excluded |
may start earliermay 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.
Access: Rights uncertain: a paved hydro service road climbing the Afon Porth-llwyd gorge above Dolgarrog, carrying a public-footpath designation on part of its length. Public access on foot applies; cycling and vehicular rights are unresolved (possibly an old unclassified county road — being checked). Ground evidence at the base: river-level warning signs — the river can rise without warning. Crown confirmed with this note (Peter, 2026-08-27).
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
© OpenStreetMap contributors · topo tiles © OpenTopoMap (CC-BY-SA) · vector tiles OpenFreeMap
Profile
The 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.
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_29_277366_20220319dtm.tif |
| Road centreline | OpenStreetMap (local PBF extract), snapshot 2026-08-10T20:21:40Z |
| Quality status | measurement confidence B; caveated windows: canopy or structure, structure excluded |
| Analysis | OCL 0.1.0, analysis 0.1.0, run chains-wales-pilot-260827, calculated 2026-08-27 |
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_29_277366_20220319dtm.tif"
],
"calculated_at": "2026-08-27T06:14:00+00:00",
"road_source": "OpenStreetMap (local PBF extract)",
"road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
"osm_pbf_path": "data/cache/pbf/wales-2026-08-11.osm.pbf",
"osm_snapshot": "2026-08-10T20:21:40Z",
"run_id": "chains-wales-pilot-260827",
"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_29_277366_20220319dtm.tif"
],
"elevation_capture_dates": [
"19-03-2022"
],
"climb_origin": "discovered",
"naming_note": "auto-named from gazetteer; was discovered-street-53-1793-3-8400",
"license": "ODbL-1.0",
"license_url": "https://howsteep.org/licensing.html"
}