Horner's Green to Castling's Heath°
1791.5 m · net rise 29.0 m · total ascent 52.2 m · overall 1.6% · confidence: high · Groton · Suffolk
Shape: stepped — 55% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 59 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.
° 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 (52.0415, 0.8700)'). Corrections welcome.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | ≈36% | 276–278 m | under overhead cover |
| 3 m (diagnostic) | 35% | 276–279 m | |
| 5 m | 33% | 276–281 m | |
| 10 m | 32% | 275–285 m | |
| 20 m | 25.2% | 268–288 m | |
| 25 m | 22.0% | 269–294 m | |
| 50 m | 15.4% | 241–291 m | |
| 100 m | 14.3% | 191–291 m |
≈ appears only on the 2–3 m diagnostic rows here, which does not lower the confidence letter: those windows are never headline values or ranking keys, so confidence reflects the standard (5–100 m) windows — which are clean on this climb.
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
© 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/england/bulk_dtm_1m/TL9540.tif"
],
"calculated_at": "2026-08-19T18:25:42+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": [
"TL9540.tif"
],
"climb_origin": "discovered",
"notes": "Coarse pass: max 9.3% over 200 m (Terrain 50), gain 27.5 m over 1741 m way. EXTENDED by graph walk: +0 segment(s) at base, +1 at top (stop: base=no_descending_continuation, top=no_ascending_continuation; min_avg=2.0%). Review before adopting. ADOPTED (England launch slice 2026-08-16): clean-steep. AUTO-NAMED from gazetteer (hypothesis, unreviewed): was 'Discovered lane (52.0415, 0.8700)'.",
"naming_note": "auto-named from gazetteer (hypothesis, unreviewed); discovered as 'Discovered lane (52.0415, 0.8700)'"
}