Porteineralpstrasse
2789.0 m · net rise 311.6 m · total ascent 325.5 m · overall 11.2% · evidence quality B (good) · Cazis · Graubünden/Grischun/Grigioni · share
Shape: sustained — 30% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 417 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 swisstopo’s swissTLM3D road model, OpenStreetMap and a second terrain model, 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.
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | ≈39% | 1505–1507 m | under overhead cover terrain reads 167.9% at 676–678 m across a structure — excluded |
| 3 m (diagnostic) | ≈38% | 1505–1508 m | under overhead cover terrain reads 111.0% at 676–679 m across a structure — excluded |
| 5 m | ≈31% | 1890–1895 m | under overhead cover terrain reads 87.4% at 676–681 m across a structure — excluded |
| 10 m | ≈24% | 1885–1895 m | under overhead cover terrain reads 52.6% at 676–686 m across a structure — excluded |
| 20 m | ≈18.8% | 2674–2694 m | under overhead cover terrain reads 39.8% at 2615–2635 m across a structure — excluded |
| 25 m | ≈17.7% | 2715–2740 m | under overhead cover terrain reads 37.5% at 2614–2639 m across a structure — excluded |
| 50 m | ≈16.4% | 2707–2757 m | under overhead cover terrain reads 29.0% at 2614–2664 m across a structure — excluded |
| 100 m | ≈15.5% | 2342–2442 m | under overhead cover terrain reads 21.6% at 2594–2694 m across a structure — excluded |
may continue beyond end Extent detection suggests reviewing where this climb starts/ends.
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 throughout, according to swisstopo's swissTLM3D road model.
Access: Listed 2026-09-11 (spike-at-maximum detector, Peter on Luderastrasse): the published maximum is a 10 m spike with a dip just before it and no sustained steepness around it — a culvert, deck or bank the line crosses, not the road. Held from the rankings until the window is re-sited with a mask.
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%
© OpenStreetMap contributors · topo tiles © OpenTopoMap (CC-BY-SA) · vector tiles OpenFreeMap · aerial imagery © swisstopo
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 | swisstopo swissALTI3D — swissALTI3D 0.5 m DTM (Federal Office of Topography swisstopo) |
|---|---|
| Resolution / CRS | 0.5 m grid, EPSG:2056; sampled every 1.0 m, bilinear interpolation |
| Tiles | 2749-1174, 2749-1175, 2750-1174, 2750-1175 |
| Road centreline | OpenStreetMap (local PBF extract) |
| Quality status | evidence quality B; caveated windows: structure excluded, texture excluded |
| Analysis | OCL 0.1.0, analysis 0.1.0, run spike-remeasure-260915, calculated 2026-09-15 |
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:2056",
"elevation_resolution_m": 0.5,
"elevation_tiles": [
"data/cache/ch/swissalti3d_2023_2749-1174_0.5_2056_5728.tif",
"data/cache/ch/swissalti3d_2023_2749-1175_0.5_2056_5728.tif",
"data/cache/ch/swissalti3d_2023_2750-1174_0.5_2056_5728.tif",
"data/cache/ch/swissalti3d_2023_2750-1175_0.5_2056_5728.tif"
],
"calculated_at": "2026-09-15T04:24:31+00:00",
"road_source": "OpenStreetMap (local PBF extract)",
"road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
"osm_pbf_path": "output/spike-remeasure/batch-switzerland.pbf",
"osm_snapshot": "",
"run_id": "spike-remeasure-260915",
"elevation_provider": "swisstopo swissALTI3D",
"elevation_licence": "swisstopo open government data (OGD): free use, attribution '\u00a9 swisstopo' \u2014 https://www.swisstopo.admin.ch/en/terms-and-conditions",
"elevation_dataset": "swissALTI3D 0.5 m DTM (Federal Office of Topography swisstopo)",
"elevation_tile_ids": [
"2749-1174",
"2749-1175",
"2750-1174",
"2750-1175"
],
"climb_origin": "discovered",
"canopy_check": "unavailable \u2014 no surface model (DSM or point cloud) registered for this coverage",
"structure_own_ways": "none \u2014 the route carried no way list; own decks unmasked",
"license": "ODbL-1.0",
"license_url": "https://howsteep.org/licensing"
}