Milltir Gerrig
5940.0 m · net rise 324.9 m · total ascent 337.2 m · overall 5.5% · confidence: good · Llangynog · Powys · share
Shape: sustained — 31% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 207 m.
Matches: Wikipedia — Milltir Gerrig (Milltir Cerrig) — articles in English and Welsh; route passes 11 m from the pass point.
≈ Overhead cover (tree canopy or structures) spans 6% 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) | ≈32% | 4201–4203 m | under overhead cover terrain reads 40.1% at 4302–4304 m across a structure — excluded |
| 3 m (diagnostic) | ≈25% | 4200–4203 m | under overhead cover terrain reads 47.1% at 4303–4306 m across a structure — excluded |
| 5 m | ≈19% | 4198–4203 m | under overhead cover terrain reads 29.6% at 4302–4307 m across a structure — excluded |
| 10 m | ≈13% | 4193–4203 m | under overhead cover terrain reads 21.0% at 4296–4306 m across a structure — excluded |
| 20 m | ≈11.5% | 374–394 m | under overhead cover terrain reads 13.2% at 4286–4306 m across a structure — excluded |
| 25 m | ≈11.3% | 313–338 m | under overhead cover terrain reads 11.6% at 4281–4306 m across a structure — excluded |
| 50 m | 11.1% | 98–148 m | |
| 100 m | ≈11.1% | 96–196 m | under overhead cover |
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.
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.
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© 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": [
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"calculated_at": "2026-08-13T02:12:03+00:00",
"road_source": "wales-discovered-adopted-routes/discovered-lane-52-8510-3-4350.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",
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],
"elevation_capture_dates": [
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],
"route_summit_trim_m": 1437.4,
"route_summit_trim_loss_m": 20.7,
"climb_origin": "discovered",
"notes": "Coarse pass: max 11.6% over 200 m (Terrain 50), gain 295.2 m over 7234 m way. EXTENDED by graph walk: +1 segment(s) at base, +0 at top (stop: base=no_descending_continuation, top=no_ascending_continuation; min_avg=2.0%). Review before adopting. DEDUPE: absorbed 1 overlapping proposal(s): discovered-lane-52-8483-3-4321 ADOPTED (notable slice 2026-08-11): big-gain. AUTO-NAMED from gazetteer (hypothesis, unreviewed): was 'Discovered lane (52.8510, -3.4350)'.",
"renamed": "2026-08-13: 'Milltir Gerrig' adopted over auto-name 'Llangynog to Cwm Pydew' \u2014 identification-certain (11 m from Wikidata pass point; en+cy Wikipedia); standing policy per Peter",
"license": "ODbL-1.0",
"license_url": "https://howsteep.org/licensing.html"
}