Lane near Blaen-y-Glyn
1515.4 m · gain 179.5 m · overall 11.8% · Bannau Brycheiniog · Powys
Shape: sustained — 32% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 703 m.
Documented on the ground — tag: 20% (2026). Signs get repainted and tags get retagged, so the date is part of the fact; on no cycling list we know of.
≈ Overhead cover (tree canopy or structures) spans 12% 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, not wrong. Longer windows average over more clean ground and are steadier.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | ≈40.8% | 156–158 m | under overhead cover terrain reads 107.0% at 14–16 m across a structure — excluded |
| 3 m (diagnostic) | ≈36.2% | 156–159 m | under overhead cover terrain reads 94.7% at 14–17 m across a structure — excluded |
| 5 m | ≈26.6% | 155–160 m | under overhead cover terrain reads 73.2% at 12–17 m across a structure — excluded |
| 10 m | ≈20.8% | 116–126 m | under overhead cover terrain reads 45.2% at 12–22 m across a structure — excluded |
| 20 m | ≈19.9% | 107–127 m | under overhead cover terrain reads 26.8% at 12–32 m across a structure — excluded |
| 25 m | ≈19.7% | 105–130 m | under overhead cover terrain reads 22.7% at 12–37 m across a structure — excluded |
| 50 m | 17.7% | 102–152 m | |
| 100 m | 15.9% | 223–323 m |
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
© OpenStreetMap contributors · topo tiles © OpenTopoMap (CC-BY-SA) · vector tiles OpenFreeMap
Profile
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_20_305216_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_305217_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_306216_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_306217_20220112dtm.tif"
],
"calculated_at": "2026-08-12T09:12:05+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",
"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_20_305216_20220112dtm.tif",
"wg_del_20_305217_20220112dtm.tif",
"wg_del_20_306216_20220112dtm.tif",
"wg_del_20_306217_20220112dtm.tif"
],
"elevation_capture_dates": [
"12-01-2022"
],
"climb_origin": "osm_incline",
"signed_gradient_pct": 20.0,
"signed_source": "OSM incline tag -20% (editors=1, first tagged 2021-03-13)",
"notes": "Promoted automatically from triage verdict=validated. Named from nearest OSM place node (Blaen-y-Glyn); originally unnamed at (51.8458, -3.3673). EXTENDED by graph walk: +1 segment(s) at base, +1 at top (stop: base=no_descending_continuation, top=no_ascending_continuation; min_avg=2.0%). Review before adopting."
}