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 "diagnostic_note": "Windows <=3 m are at raster-noise scale (roughly +/-2 pp on a 1 m DTM). Diagnostic use only: never a headline or ranking value.",
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  "calculated_at": "2026-08-12T09:11:46+00:00",
  "road_source": "OpenStreetMap (local PBF extract)",
  "road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
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  "osm_timestamps": {
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   "103333437": "2026-03-11 04:39:45+00:00"
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  "osm_retrieved_at": "2026-08-12T09:11:45+00:00",
  "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": [
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  "elevation_capture_dates": [
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  "climb_origin": "named",
  "signed_gradient_pct": 32,
  "signed_source": "Road sign at foot of hill. OSM tag history dates the change: incline=-25% from 2013 (user Pobice), updated to -32% on 2025-10-22 (changeset 173626481, user Fgjgdrou). Two independent mappers 12 years apart = strong sign evidence.",
  "notes": "Golden regression case. Aberystwyth. Sibling segment 218612916 still carries the stale -25% \u2014 both sign eras preserved in OSM."
 },
 "area": {
  "place": "Cwmpadarn",
  "county": "Sir Ceredigion - Ceredigion"
 },
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  "shape_class": "sustained"
 }
}