LIVING SURVEY — measurements are reviewed continuously as new data and local evidence arrive. Seen a sign, a gate, or a better name? Submit an update no account needed · photos welcome via GitHub

Constitution Hill

347.9 m · net rise 60.6 m · overall 17.4% · evidence quality A (high) · Abertawe · West Glamorgan · share

Shape: sustained — 30% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 287 m.

Matches: Wikipedia, 100 Greatest Cycling Climbs (Simon Warren) — Constitution Hill, Swansea — has its own article — No. 100 (verified in the official 100 Climbs app, 2026 numbering) — the series finale is in Swansea.

Gradient ladder what do windows mean?

Window	Maximum	Located at
2 m (diagnostic)	24%	309–311 m
3 m (diagnostic)	24%	309–312 m
5 m	23%	309–314 m
10 m	22%	307–317 m
20 m	21.9%	161–181 m
25 m	21.9%	309–334 m
50 m	21.6%	297–347 m
100 m	21.2%	81–181 m

Measured on the mapped road line; moving the line 1 m either way reads 21.7–22.0% over 25 m.

may 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

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%

Constitution Hill LiDAR hillshade map with contours

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	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_21_264193_20220113dtm.tif
Road centreline	OpenStreetMap (local PBF extract), snapshot 2026-08-10T20:21:40Z
Quality status	evidence quality A; no review flags; no caveated windows
Analysis	OCL 0.1.0, analysis 0.1.0, run identifier not recorded (legacy measurement, before the campaign driver stamped runs), calculated 2026-08-12

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_21_264193_20220113dtm.tif"
  ],
  "calculated_at": "2026-08-12T09:06:25+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_21_264193_20220113dtm.tif"
  ],
  "elevation_capture_dates": [
    "13-01-2022"
  ],
  "climb_origin": "discovered",
  "license": "ODbL-1.0",
  "license_url": "https://howsteep.org/licensing"
}