{
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 "diagnostic_note": "Windows <=3 m are at raster-noise scale (1-sigma raster noise alone is roughly +/-7 pp at 2 m and +/-5 pp at 3 m on a 1 m DTM). Diagnostic use only: never a headline or ranking value.",
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      "mask-edge",
      "",
      ""
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 },
 "provenance": {
  "analysis_version": "0.1.0",
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   "numpy": "2.5.3",
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   "pyosmium": "4.3.1",
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   "gdal": "3.12.4",
   "proj": "9.8.1",
   "run_id": "remeasure-260920-uk",
   "road_pbf": "batch-wales-chunk010.pbf",
   "region_key": "wales",
   "crs": "EPSG:27700",
   "elevation_provider_key": "wales",
   "authority": "os-open-roads",
   "registry_pbf": "wales-2026-08-11.osm.pbf"
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  "calculated_at": "2026-09-21T02:15:09+00:00",
  "road_source": "OpenStreetMap (local PBF extract)",
  "road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
  "osm_pbf_path": "output/remeasure-260920/uk/batch-wales-chunk010.pbf",
  "osm_snapshot": "",
  "run_id": "remeasure-260920-uk",
  "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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   "wg_del_14_233213_20210321dtm.tif"
  ],
  "elevation_capture_dates": [
   "21-03-2021"
  ],
  "climb_origin": "discovered",
  "structure_own_ways": "none \u2014 the route carried no way list; own decks unmasked",
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   "stations": 70,
   "stations_resolved": 70,
   "width_median_m": 3.5,
   "width_p10_m": 2.0,
   "width_min_m": 1.25,
   "width_max_m": 12.0,
   "bounded_share": 0.414,
   "unbounded_share": 0.586,
   "confidence_median": 0.0,
   "width_median_bounded_m": 3.25,
   "window_m": [
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    400.0
   ],
   "width_at_max25_m": 4.0,
   "window_stations": 6,
   "single_track": false,
   "single_track_rule": "PROVISIONAL (2026-09-15): width_p10_m <= 3.0 m with bounded_share >= 0.6; recorded, not a rule",
   "status": "ok",
   "source": "dtm",
   "station_m": 25.0,
   "window_station_m": 5.0,
   "halfwidth_m": 6.0,
   "step_m": 0.25,
   "level_tol_m": 0.12,
   "break_min_m": 0.3,
   "stations_failed": 0,
   "hedge_to_hedge": {
    "stations": 70,
    "stations_resolved": 70,
    "width_median_m": 4.0,
    "width_p10_m": 2.23,
    "width_min_m": 1.0,
    "width_max_m": 12.0,
    "bounded_share": 0.829,
    "unbounded_share": 0.171,
    "confidence_median": 1.0,
    "width_median_bounded_m": 3.75,
    "window_m": [
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    ],
    "width_at_max25_m": 2.62,
    "window_stations": 6,
    "status": "ok",
    "source": "dsm",
    "station_m": 25.0,
    "window_station_m": 5.0,
    "halfwidth_m": 6.0,
    "step_m": 0.25,
    "level_tol_m": 0.5,
    "break_min_m": 0.3,
    "stations_failed": 0
   }
  },
  "unmapped_bridge_span": {
   "start_m": 215.0,
   "end_m": 389.0,
   "span_m": 174.0,
   "floor_at_m": 275.0,
   "depth_m": 11.4,
   "drop_m": 5.3,
   "surface": "raw",
   "window_start_m": 375.0,
   "window_end_m": 400.0,
   "gap_m": 0.0,
   "unstable": false,
   "perturbation_hits": 3,
   "note": "The ground falls 5 m below the road between 215 m and 389 m \u2014 11 m below the straight line joining the profile either side of it \u2014 and climbs back to that line, with the steepest 25 m at 375 m. That is a ravine under a deck OSM does not tag as a bridge, so no mask fired. Re-measure with mask_ranges_m over the span before this maximum stands (unmapped-bridge-span, Peter 2026-09-20)."
  },
  "remeasured": {
   "on": "2026-09-21",
   "why": "corpus re-measure 2026-09-21: a mask that exists today reaching a page published before it did; fallers only (Peter: fold the fallers)",
   "published_max25_pct": 24.84,
   "max25_pct": 22.98
  },
  "license": "ODbL-1.0",
  "license_url": "https://howsteep.org/licensing"
 },
 "area": {
  "place": "Coomb",
  "county": "Sir Gaerfyrddin - Carmarthenshire"
 },
 "review_flags": [
  {
   "kind": "possible-bridge-or-hollow",
   "span_m": [
    215.0,
    389.0
   ],
   "status": "pending-human-review",
   "noted": "2026-09-21",
   "figure_adjusted": false
  }
 ]
}