Porlock Hill°
4391.6 m · net rise 295.8 m · total ascent 310.0 m · overall 6.7% · evidence quality B (good) · Porlock · Somerset · share
Shape: stepped — 45% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 668 m.
Matches: 100 Greatest Cycling Climbs (Simon Warren).
° 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 (hypothesis, unreviewed); discovered as 'Discovered lane (51.2046, -3.6451)'). Corrections welcome.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | 30% | 1870–1872 m | |
| 3 m (diagnostic) | ≈26% | 22–25 m | under overhead cover |
| 5 m | ≈25% | 22–27 m | under overhead cover |
| 10 m | ≈24% | 18–28 m | under overhead cover |
| 20 m | ≈20.1% | 12–32 m | under overhead cover |
| 25 m | ≈19.7% | 0–25 m | under overhead cover |
| 50 m | 18.6% | 121–171 m | |
| 100 m | 17.6% | 469–569 m |
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.
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 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).
Measurement card
| Elevation | Environment Agency — EA LIDAR Composite DTM 1m (2022) |
|---|---|
| Resolution / CRS | 1.0 m grid, EPSG:27700; sampled every 1.0 m, bilinear interpolation |
| Tiles | SS8045.tif, SS8545.tif |
| Road centreline | OpenStreetMap (local PBF extract), snapshot 2026-08-12T20:21:46Z |
| Quality status | evidence quality B; caveated windows: canopy or structure |
| Analysis | OCL 0.1.0, analysis 0.1.0, run identifier not recorded (legacy measurement, before the campaign driver stamped runs), calculated 2026-08-20 |
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/england/bulk_dtm_1m/SS8045.tif",
"data/cache/england/bulk_dtm_1m/SS8545.tif"
],
"calculated_at": "2026-08-20T12:08:00+00:00",
"road_source": "OpenStreetMap (local PBF extract)",
"road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
"osm_pbf_path": "data/cache/pbf/england-2026-08-12.osm.pbf",
"osm_snapshot": "2026-08-12T20:21:46Z",
"elevation_provider": "Environment Agency",
"elevation_dataset": "EA LIDAR Composite DTM 1m (2022)",
"elevation_licence": "Open Government Licence v3 \u2014 \u00a9 Environment Agency",
"elevation_coverage_id": "13787b9a-26a4-4775-8523-806d13af58fc__Lidar_Composite_Elevation_DTM_1m",
"elevation_tile_ids": [
"SS8045.tif",
"SS8545.tif"
],
"climb_origin": "discovered",
"naming_note": "auto-named from gazetteer (hypothesis, unreviewed); discovered as 'Discovered lane (51.2046, -3.6451)'",
"license": "ODbL-1.0",
"license_url": "https://howsteep.org/licensing",
"naming": {
"previous_name": "Porlock to Pittcombe Head",
"renamed": "2026-09-13",
"rule": "identification-certain (CLAUDE.md, Peter 2026-08-13)",
"evidence": "The page absorbed the OSM proposals porlock-hill, porlock-hill-2 and porlock-hill-3 \u2014 ways 28642997, 271016530 and 271016532, each carried in climbs/eng-geo-05.yaml as a way named \"Porlock Hill\" and all present in this route's source_way_ids \u2014 and the line runs from Porlock village (its lowest 385 m trimmed 2026-08-20 on Peter's verdict, so the page is the hill above the village) up to Pittcombe Head, the whole of the hill described by Wikipedia's \"Porlock Hill\" article.",
"by": "Peter 2026-09-13"
}
}