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"end_elevation_m": 370.17820257432254, "start_xy": [ 271083.57216685085, 219322.64424014412 ], "end_xy": [ 271121.9397009821, 219290.88040510626 ] }, "min_100m": { "gradient_pct": -4.255813354990835, "start_distance_m": 1872.0, "end_distance_m": 1972.0, "midpoint_distance_m": 1922.0, "start_elevation_m": 374.1100551438186, "end_elevation_m": 369.8542417888278, "start_xy": [ 271066.2383442358, 219332.53272190376 ], "end_xy": [ 271145.09743000864, 219271.8186627187 ] } }, "diagnostic_window_maxima": { "max_2m": { "gradient_pct": 32.05152688122723, "start_distance_m": 887.0, "end_distance_m": 889.0, "midpoint_distance_m": 888.0, "start_elevation_m": 297.5240139980752, "end_elevation_m": 298.16504453569974, "start_xy": [ 270480.763883416, 219573.48514694363 ], "end_xy": [ 270479.9258945427, 219571.66916934238 ] }, "max_3m": { "gradient_pct": 29.6494819808629, "start_distance_m": 887.0, "end_distance_m": 890.0, "midpoint_distance_m": 888.5, "start_elevation_m": 297.5240139980752, "end_elevation_m": 298.4134984575011, "start_xy": [ 270480.763883416, 219573.48514694363 ], "end_xy": [ 270479.5069001061, 219570.76118054177 ] } }, "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.", "quality_summary": { "overhead_obstruction": { "obstruction_threshold_m": 2.0, "obstructed_fraction": 0.024, "obstruction_max_height_m": 18.24, "flagged_windows_m": [ 100 ] }, "review": [], "extent": [ "descends_at_start" ] }, "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/wales/dtm_1m/wg_del_21_270218_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_270219_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_270220_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_271218_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_271219_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_271220_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_272218_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_272219_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_272220_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_273218_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_273219_20220113dtm.tif", "data/cache/wales/dtm_1m/wg_del_21_273220_20220113dtm.tif" ], "calculated_at": "2026-08-12T09:07:18+00:00", "road_source": "OpenStreetMap (local PBF extract)", "road_attribution": "\u00a9 OpenStreetMap contributors, ODbL", "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": [ "wg_del_21_270218_20220113dtm.tif", "wg_del_21_270219_20220113dtm.tif", "wg_del_21_270220_20220113dtm.tif", "wg_del_21_271218_20220113dtm.tif", "wg_del_21_271219_20220113dtm.tif", "wg_del_21_271220_20220113dtm.tif", "wg_del_21_272218_20220113dtm.tif", "wg_del_21_272219_20220113dtm.tif", "wg_del_21_272220_20220113dtm.tif", "wg_del_21_273218_20220113dtm.tif", "wg_del_21_273219_20220113dtm.tif", "wg_del_21_273220_20220113dtm.tif" ], "elevation_capture_dates": [ "13-01-2022" ], "climb_origin": "discovered", "notes": "Coarse pass: max 9.0% over 200 m (Terrain 50), gain 44.4 m over 2025 m way. EXTENDED by graph walk: +4 segment(s) at base, +4 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-51-8619-3-8799 ADOPTED (notable slice 2026-08-11): big-gain. AUTO-NAMED from gazetteer (hypothesis, unreviewed): was 'Discovered lane (51.8578, -3.8696)'.", "naming_note": "auto-named from gazetteer (hypothesis, unreviewed); discovered as 'Discovered lane (51.8578, -3.8696)'" }, "area": { "place": "Cwm Nant-dywyll", "county": "Sir Gaerfyrddin - Carmarthenshire" }, "reported_claims": [], "confidence": "B", "shape": { "ascent_concentration": 0.43, "concentration_window_frac": 0.25, "longest_pitch_10pct_m": 211.0, "shape_class": "sustained" } }