Paved · ranked
1801.7 m · net rise 124.1 m · total ascent 141.0 m · overall 6.9% · evidence quality B (good) · Lasse · Pyrénées-Atlantiques
Shape: sustained — 39% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 247 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 IGN’s BD TOPO® road network, OpenStreetMap and the classified LiDAR HD point cloud, 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.
needs review short window divergence — treat short-window maxima here as provisional.
≈ Overhead cover (tree canopy or structures) spans 26% of this route — detected by comparing the surface model (DSM, treetops and rooftops) against the terrain model (DTM, bare ground). Under cover the bare-ground model is built from fewer laser returns, so metre-scale readings can wobble; maxima whose window sits in a covered zone are marked ≈ below — less certain — the flag does not say whether the true value is higher or lower. Longer windows average over more clean ground and are steadier.
Chemin d'Ithurxilo (Lasse, Pyrénées-Atlantiques) is 1801.7 m long at 6.9% overall; its steepest 25 m averages ≈20.3% and its steepest 100 m ≈16.3%, measured from IGN's LiDAR HD 0.5 m laser surveys along the mapped road centreline.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | ≈32% | 961–963 m | under overhead cover terrain reads 46.0% at 945–947 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 3 m (diagnostic) | ≈31% | 961–964 m | under overhead cover terrain reads 41.6% at 1698–1701 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 5 m | ≈28% | 961–966 m | under overhead cover terrain reads 35.7% at 1697–1702 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 10 m | ≈22% | 1709–1719 m | under overhead cover terrain reads 28.7% at 1692–1702 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 20 m | ≈21.1% | 1709–1729 m | under overhead cover terrain reads 24.6% at 1684–1704 m across a structure and terrain that holds no road surface (dense canopy, no bench) — excluded |
| 25 m | ≈20.3% | 1709–1734 m | under overhead cover terrain reads 23.4% at 1679–1704 m across a structure — excluded |
| 50 m | ≈17.7% | 1040–1090 m | under overhead cover terrain reads 21.0% at 1679–1729 m across a structure — excluded |
| 100 m | ≈16.3% | 999–1099 m | under overhead cover terrain reads 17.8% at 1669–1769 m across a structure — excluded |
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.
Surface: paved (8% unpaved), according to BD TOPO®, IGN's national topographic database: paved for the first 1,652 m; unpaved from 1,652 m to the top. The steepest 25 m lies on the unpaved part.
Access: Ranked 2026-10-24: IGN BD TOPO carries 100% of the route as public road (0% restricted), which answers the OSM audit question (untagged surface).
Measured, not vetted. This page records what the laser record shows about the road's shape — nothing more. Nobody has necessarily ridden or inspected this road for the survey, and a page here is not a recommendation and no guarantee that the road is open, surfaced, rideable or safe. Gates, private sections, missing rights of way and hazards do not show up in elevation data. Check access and conditions on the ground and make your own judgment.
Ridden it, or know better? Submit data for this climb no account needed · Share this climb
Route colour = gradient over a 25 m window: <10% 10–20% 20–25% ≥25%
Route line = the road surface as the LiDAR survey finds it. Basemap roads are for orientation and may sit a few metres off.
© OpenStreetMap contributors · topo tiles © OpenTopoMap (CC-BY-SA) · vector tiles OpenFreeMap · aerial imagery © IGN, BD ORTHO® (Licence Ouverte Etalab 2.0)
Profile
The map, profile and gradient chart share one position — move your pointer over them and the marker follows. Colors are the gradient bands; the shaded span is the steepest 25 m. Any 25 m figure is good to about a point either way (why).
Measurement card
| Elevation | IGN LiDAR HD MNT 0.5 m — LiDAR HD — MNT (sol) et MNS (surface), 0,50 m (Institut national de l'information géographique et forestière), RGF93 / Lambert-93 EPSG:2154, altitudes IGN69 |
|---|---|
| Resolution / CRS | 0.5 m grid, EPSG:2154; sampled every 1.0 m, bilinear interpolation |
| Tiles | E351-N6237, E352-N6237, E353-N6237 |
| Road centreline | OpenStreetMap (local PBF extract) |
| Quality status | evidence quality B; review flags: short window divergence |
| Analysis | OCL 0.1.0, analysis 0.1.0, run remeasure-260929c-fr, calculated 2026-09-29 |
Provenance
{
"analysis_version": "0.1.0",
"run_manifest": {
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"code_git_sha": "1c1dcd6ab03c87d3448f21732228db610cfcad7e",
"code_git_dirty": "false",
"analysis_version": "0.1.0",
"analysis_config_digest": "sha256:8c94015b54267da4",
"python": "3.14.4",
"numpy": "2.5.3",
"rasterio": "1.5.1",
"pyproj": "3.8.0",
"laspy": "2.7.0",
"shapely": "2.1.2",
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"libosmium": "2.23.1",
"gdal": "3.12.4",
"proj": "9.8.1",
"run_id": "remeasure-260929c-fr",
"road_pbf": "batch-france-chunk007.pbf",
"region_key": "france",
"crs": "EPSG:2154",
"elevation_provider_key": "ign-lidarhd",
"tile_index": "wms-grid",
"authority": "bdtopo",
"registry_pbf": "france-vosges-2026-09-16.osm.pbf",
"tile_index_snapshot": "sha256:d7b2f8b890686447"
},
"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:2154",
"elevation_resolution_m": 0.5,
"elevation_tiles": [
"data/cache/fr/ign-lidarhd_dtm_E351-N6237_0m5@21LHD1EQ-2025-09-26.tif",
"data/cache/fr/ign-lidarhd_dtm_E352-N6237_0m5@21LHD1EQ-2025-09-26.tif",
"data/cache/fr/ign-lidarhd_dtm_E353-N6237_0m5@21LHD1EQ-2025-09-26.tif"
],
"calculated_at": "2026-09-29T16:09:15+00:00",
"road_source": "OpenStreetMap (local PBF extract)",
"road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
"osm_pbf_path": "output/remeasure-260929c-pyr/fr/batch-france-chunk007.pbf",
"osm_snapshot": "",
"run_id": "remeasure-260929c-fr",
"elevation_provider": "IGN LiDAR HD MNT 0.5 m",
"elevation_licence": "Licence Ouverte / Open Licence 2.0 (Etalab) \u2014 \u00a9 IGN, LiDAR HD (MNT/MNS), data.geopf.fr; reproduction autoris\u00e9e avec mention de la source et de la date",
"elevation_dataset": "LiDAR HD \u2014 MNT (sol) et MNS (surface), 0,50 m (Institut national de l'information g\u00e9ographique et foresti\u00e8re), RGF93 / Lambert-93 EPSG:2154, altitudes IGN69",
"elevation_vertical_datum": "IGN69",
"elevation_tile_ids": [
"E351-N6237",
"E352-N6237",
"E353-N6237"
],
"elevation_blocks": [
"21LHD1EQ@2025-09-26"
],
"ign_dalles": [
"LHD_FXX_0351_6238_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_0352_6238_MNT_O_0M50_LAMB93_IGN69",
"LHD_FXX_0353_6238_MNT_O_0M50_LAMB93_IGN69"
],
"ign_missions": [
"21LHD1EQ"
],
"ign_editions": [
"2025-09-26"
],
"ign_dsm_edition": {
"LHD_FXX_0351_6238_MNT_O_0M50_LAMB93_IGN69": "2025-09-26",
"LHD_FXX_0352_6238_MNT_O_0M50_LAMB93_IGN69": "2025-09-26",
"LHD_FXX_0353_6238_MNT_O_0M50_LAMB93_IGN69": "2025-09-26"
},
"climb_origin": "discovered",
"seam_filled_samples": {
"count": 0,
"distances_m": []
},
"seam_filled_in_maximum": false,
"structure_own_ways": 6,
"structure_own_ways_source": "map-matched to the road network: the entry carried no way list, so the ways the route runs along were found by geometry (ukclimb.batch.own_ways_by_geometry)",
"prior_doc": {
"slug": "chemin-d-ithurxilo",
"calculated_at": "2026-09-20T05:51:42+00:00",
"code_git_sha": "06fa4c370391",
"analysis_version": "0.1.0",
"run_id": "fr-pyr1",
"path": "output/remeasure-260929c-pyr/fr/priors/chemin-d-ithurxilo/chemin-d-ithurxilo.json",
"spans": 6,
"sources": [
"excluded_ranges_m",
"texture"
]
},
"carriageway": {
"stations": 79,
"stations_resolved": 79,
"width_median_m": 5.0,
"width_p10_m": 2.95,
"width_min_m": 1.5,
"width_max_m": 10.75,
"bounded_share": 0.329,
"unbounded_share": 0.671,
"confidence_median": 0.0,
"width_median_bounded_m": 4.75,
"window_m": [
1709.0,
1734.0
],
"width_at_max25_m": 7.0,
"window_stations": 7,
"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": 79,
"stations_resolved": 79,
"width_median_m": 5.5,
"width_p10_m": 1.2,
"width_min_m": 0.5,
"width_max_m": 10.5,
"bounded_share": 0.81,
"unbounded_share": 0.19,
"confidence_median": 1.0,
"width_median_bounded_m": 4.38,
"window_m": [
1709.0,
1734.0
],
"width_at_max25_m": 5.0,
"window_stations": 7,
"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
}
},
"remeasured": {
"on": "2026-09-29",
"why": "block-extract cache sweep: fold the fallers, risers held published (standing rulings)",
"published_max25_pct": 20.27,
"max25_pct": 20.27
},
"license": "ODbL-1.0",
"license_url": "https://howsteep.org/licensing"
}