BETA — measurements and names under active refinement. Seen a sign, a gate, or a better name? Submit an update no account needed · photos welcome via GitHub

Lon Golff

906.6 m · net rise 58.7 m · total ascent 70.2 m · overall 6.5% · confidence: good · Machroes · Gwynedd

Shape: stepped — 47% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 89 m.

Found purely from mapping and LiDAR data, and not yet matched against books, race records or lists — it may be well known to locals under a name we've never heard. It was cross-checked against the OS road network, surface models and map tags, but 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 you know this road, tell us what you found — photographs, corrections and local knowledge all welcome; the map links below let you scout it first.

≈ 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 — the flag does not say whether the true value is higher or lower. Longer windows average over more clean ground and are steadier.

Gradient ladder what do windows mean?

Window	Maximum	Located at
2 m (diagnostic)	≈50%	467–469 m	under overhead cover terrain reads 54.9% at 578–580 m across a structure — excluded
3 m (diagnostic)	43%	467–470 m
5 m	≈31%	258–263 m	under overhead cover terrain reads 32.9% at 575–580 m across a structure — excluded
10 m	31%	258–268 m
20 m	25.8%	252–272 m
25 m	23.7%	251–276 m
50 m	≈19.4%	222–272 m	under overhead cover
100 m	≈15.9%	186–286 m	under overhead cover

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

This climb's data: OCL JSON — the full gradient ladder, quality flags and provenance in the OpenClimb Ladder format.

Ridden it, or know better? Submit data for this climb no account needed

Lon Golff LiDAR hillshade map with contours

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_29_231325_20220318dtm.tif",
    "data/cache/wales/dtm_1m/wg_del_34_231326_20210302dtm.tif"
  ],
  "calculated_at": "2026-08-12T01:14:18+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_29_231325_20220318dtm.tif",
    "wg_del_34_231326_20210302dtm.tif"
  ],
  "elevation_capture_dates": [
    "02-03-2021",
    "18-03-2022"
  ],
  "climb_origin": "discovered",
  "notes": "Coarse pass: max 13.4% over 200 m (Terrain 50), gain 47.1 m over 724 m way. EXTENDED by graph walk: +2 segment(s) at base, +0 at top (stop: base=no_descending_continuation, top=no_ascending_continuation; min_avg=2.0%). Review before adopting."
}