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   "elevation_provider_key": "usa3dep",
   "authority": "usa-inventory",
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  "calculated_at": "2026-09-22T00:05:42+00:00",
  "road_source": "OpenStreetMap (local PBF extract)",
  "road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
  "osm_pbf_path": "output/valley-260921/us/batch-usa-me-chunk000.pbf",
  "osm_snapshot": "",
  "run_id": "remeasure-valley-260921-us",
  "elevation_provider": "USGS 3DEP (The National Map)",
  "elevation_licence": "Public domain \u2014 USGS 3DEP 1 m DEM, courtesy of the U.S. Geological Survey",
  "elevation_dataset": "USGS 3DEP 1 m DEM, ME_WesternMtns_B24 (collected 2024)",
  "elevation_tile_ids": [
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  "climb_origin": "discovered",
  "canopy_check": "unavailable \u2014 EPT corridor failed: ME_SouthCoastal_1_2020: no corridor points fetched; USGS_LPC_ME_NRCS_Lot4_2013_LAS_2015: no corridor points fetched; ME_Androscoggin_2009: no corridor points fetched; ME_SouthCentral_1_B22: no corridor points fetched",
  "structure_own_ways": "none \u2014 the route carried no way list and no mapped way runs along it; own decks unmasked",
  "prior_doc": {
   "slug": "thurlow-drive",
   "calculated_at": "2026-09-08T16:15:32+00:00",
   "code_git_sha": null,
   "analysis_version": "0.1.0",
   "run_id": "retro-box-260908",
   "path": "/root/uk-climbs/output/valley-260921/us/priors/thurlow-drive/thurlow-drive.json",
   "spans": 2,
   "sources": [
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  "carriageway": {
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   "stations_resolved": 30,
   "width_median_m": 4.38,
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   "width_min_m": 2.0,
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   "unbounded_share": 0.833,
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   "width_at_max25_m": 3.25,
   "window_stations": 7,
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   "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,
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   "halfwidth_m": 6.0,
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   "level_tol_m": 0.12,
   "break_min_m": 0.3,
   "stations_failed": 0,
   "hedge_to_hedge": {
    "status": "unavailable \u2014 no DSM raster (surface model absent or point-cloud only, which cannot serve off-line samples)"
   }
  },
  "unmapped_bridge_span": {
   "start_m": 197.0,
   "end_m": 353.0,
   "span_m": 156.0,
   "floor_at_m": 223.0,
   "depth_m": 11.5,
   "drop_m": 3.5,
   "surface": "raw",
   "window_start_m": 351.0,
   "window_end_m": 376.0,
   "gap_m": 0.0,
   "unstable": false,
   "perturbation_hits": 3,
   "note": "The ground falls 4 m below the road between 197 m and 353 m \u2014 12 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 351 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": "2026-09-22",
   "why": "valley-crossing extent re-measure 2026-09-22: low-to-summit (531.0 m -> 1107.0 m)",
   "published_max25_pct": 23.59,
   "max25_pct": 23.59
  },
  "license": "ODbL-1.0",
  "license_url": "https://howsteep.org/licensing"
 },
 "area": {
  "place": "Hartford",
  "county": "Maine"
 }
}