Llangynidr to Cwm Cleisfer°
2043.8 m · gain 149.0 m · overall 7.3% · Cwm Cleisfer · Powys
Shape: sustained — 35% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 94 m.
An unlisted find of this survey, on no list we know of. It was discovered by analysing LiDAR terrain data and cross-checked against the OS road network, surface models and map tags — but despite all that, a discovery can still be an artifact of the terrain model or the map. Treat it as a well-evidenced hypothesis until someone has ridden it. If that someone is you, tell us what you found — photographs, corrections and local knowledge all welcome; the map links below let you scout it first.
° The name is provisional: this climb appears on no list we know of, so it was named from nearby map places. There is no evidence of local usage — (auto-named from gazetteer (hypothesis, unreviewed); discovered as 'Discovered lane (51.8550, -3.2381)'). Corrections welcome.
≈ Overhead cover (tree canopy or structures) spans 51% 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) | ≈45.8% | 716–718 m | under overhead cover |
| 3 m (diagnostic) | ≈42.0% | 715–718 m | under overhead cover |
| 5 m | ≈38.9% | 714–719 m | under overhead cover |
| 10 m | ≈33.4% | 714–724 m | under overhead cover |
| 20 m | ≈29.0% | 714–734 m | under overhead cover |
| 25 m | ≈27.2% | 710–735 m | under overhead cover |
| 50 m | 19.1% | 1986–2036 m | |
| 100 m | ≈16.7% | 1936–2036 m | under overhead cover |
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
© 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_314217_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_314218_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_314219_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_315217_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_315218_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_315219_20220112dtm.tif"
],
"calculated_at": "2026-08-12T09:07:13+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_314217_20220112dtm.tif",
"wg_del_20_314218_20220112dtm.tif",
"wg_del_20_314219_20220112dtm.tif",
"wg_del_20_315217_20220112dtm.tif",
"wg_del_20_315218_20220112dtm.tif",
"wg_del_20_315219_20220112dtm.tif"
],
"elevation_capture_dates": [
"12-01-2022"
],
"climb_origin": "discovered",
"notes": "Coarse pass: max 12.3% over 200 m (Terrain 50), gain 26.2 m over 496 m way. EXTENDED by graph walk: +5 segment(s) at base, +4 at top (stop: base=no_descending_continuation, top=no_ascending_continuation; min_avg=2.0%). Review before adopting. DEDUPE: absorbed 2 overlapping proposal(s): discovered-lane-51-8594-3-2380, discovered-lane-51-8630-3-2340 ROAD-REVIEW: way 540512199: unnamed service way; way 540512199: service way, surface untagged; way 780818780: unnamed service way; way 780818780: service way, surface untagged ADOPTED (notable slice 2026-08-11): qualified-steep. AUTO-NAMED from gazetteer (hypothesis, unreviewed): was 'Discovered lane (51.8550, -3.2381)'.",
"naming_note": "auto-named from gazetteer (hypothesis, unreviewed); discovered as 'Discovered lane (51.8550, -3.2381)'"
}