Twyn-Garreg-Wen to Cwm Crew°
1953.0 m · gain 77.8 m · overall 4.0% · Cwm Crew · Powys
Shape: sustained — 43% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 13 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 (51.8405, -3.4639)'). Corrections welcome.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | 11.7% | 210–212 m | |
| 3 m (diagnostic) | 10.8% | 120–123 m | |
| 5 m | 10.5% | 104–109 m | |
| 10 m | 10.4% | 120–130 m | |
| 20 m | 10.1% | 121–141 m | |
| 25 m | 10.1% | 104–129 m | |
| 50 m | 10.0% | 104–154 m | |
| 100 m | 9.8% | 75–175 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
This climb's data: OCL JSON — the full gradient ladder, quality flags and provenance in the OpenClimb Ladder format.
© 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_298216_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_298217_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_298218_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_299216_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_299217_20220112dtm.tif",
"data/cache/wales/dtm_1m/wg_del_20_299218_20220112dtm.tif"
],
"calculated_at": "2026-08-12T23:12:27+00:00",
"road_source": "trunk-adopted-routes/discovered-lane-51-8405-3-4639.geojson",
"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_298216_20220112dtm.tif",
"wg_del_20_298217_20220112dtm.tif",
"wg_del_20_298218_20220112dtm.tif",
"wg_del_20_299216_20220112dtm.tif",
"wg_del_20_299217_20220112dtm.tif",
"wg_del_20_299218_20220112dtm.tif"
],
"elevation_capture_dates": [
"12-01-2022"
],
"climb_origin": "discovered",
"notes": "Coarse pass: max 9.5% over 200 m (Terrain 50), gain 64.8 m over 1464 m way. EXTENDED by graph walk: +0 segment(s) at base, +2 at top (stop: base=no_descending_continuation, top=no_ascending_continuation; min_avg=2.0%). Review before adopting. ADOPTED (trunk sweep, Peter's on-sight verdict 2026-08-12): clean table, adopt-all. AUTO-NAMED from gazetteer (hypothesis, unreviewed): was 'Discovered lane (51.8405, -3.4639)'.",
"naming_note": "auto-named from gazetteer (hypothesis, unreviewed); discovered as 'Discovered lane (51.8405, -3.4639)'"
}