Data sources
TrailSplits is built on open data. This page lists every outside source behind the maps, routes, elevation, aerial imagery and snow: what it is used for, its licence, the credit it asks for, and whether copies may be kept on your phone for offline use. Facts on race and trail pages, such as dates or official notices, are cited on those pages.
Last checked 25 September 2026.
In use
OpenStreetMap
The map itself, routing, search, huts and stops, marked hiking routes, and the trails behind the guides.
- Licence
- ODbL-1.0
- Credit
- © OpenStreetMap contributors
- Offline
- allowed, with the credit
- Terms
- https://www.openstreetmap.org/copyright
OpenMapTiles schema and cartography
The layout and style of the base map.
- Licence
- CC-BY-4.0 (design), BSD-3-Clause (code)
- Credit
- © OpenMapTiles, linked to https://openmaptiles.org/
- Offline
- allowed, with the credit
- Terms
- https://github.com/openmaptiles/openmaptiles/blob/master/LICENSE.md
Copernicus DEM GLO-30
Heights: route elevation profiles, relief shading, contour lines and the 3D terrain.
- Licence
- Copernicus DEM licence (free, with the notice on adapted products)
- Credit
- Terrain and contours produced using Copernicus WorldDEM-30 © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018 provided under COPERNICUS by the European Union and ESA; all rights reserved
- Offline
- allowed, with the notice
- Terms
- https://dataspace.copernicus.eu/explore-data/data-collections/copernicus-contributing-missions/collections-description/COP-DEM
Natural Earth
Country borders that decide which national aerial imagery is shown where, and the map at low zoom.
- Licence
- public-domain
- Credit
- none required
- Offline
- allowed
- Terms
- https://www.naturalearthdata.com/about/terms-of-use/
Copernicus Sentinel-2, TrailSplits' late-summer mosaic
TrailSplits' own late-summer satellite mosaic, the aerial view where no national imagery is open (Aosta, the Dolomites outside South Tyrol, Madeira, Iceland, Lapland and more).
- Licence
- copernicus-open
- Credit
- Contains modified Copernicus Sentinel data 2023-2026
- Offline
- allowed, with the credit
- Terms
- https://sentinels.copernicus.eu
Official national orthophotos
The aerial view, from each country's official open orthophotos, each shown only inside its own country.
- swisstopo SWISSIMAGE (Switzerland and Liechtenstein)
© swisstopo · swisstopo-OGD · terms - IGN BD ORTHO (France)
IGN – BD ORTHO (Licence Ouverte 2.0) · etalab-2.0 · terms - basemap.at Orthofoto (Austria)
Datenquelle: basemap.at · CC-BY-4.0 · terms - IGN España PNOA (Spain)
PNOA CC BY 4.0 scne.es · CC-BY-4.0 · terms - Bayerische Vermessungsverwaltung DOP (Bavaria)
© Datenquellen: Bayerische Vermessungsverwaltung, Europäische Union, enthält Copernicus Sentinel-2 Daten 2018, verarbeitet durch das BKG · CC-BY-4.0 · terms - USGS The National Map orthoimagery (NAIP) (the contiguous United States)
USDA, USGS The National Map: Orthoimagery · public-domain · terms - Autonome Provinz Bozen – Südtirol, Orthofoto 2023 (South Tyrol)
Orthofoto 2023 © Autonome Provinz Bozen – Südtirol (CC BY 4.0) · CC-BY-4.0 · terms - GURS digitalni ortofoto (DOF025) (Slovenia)
Geodetska uprava Republike Slovenije, DOF025 (CC BY 4.0) · CC-BY-4.0 · terms - DGT OrtoSat 2023 (mainland Portugal)
OrtoSat 2023 © Direção-Geral do Território (CC BY 4.0) · CC-BY-4.0 · terms - Provincia autonoma di Trento, Ortofoto 2015 (20 cm) (Trentino)
Ortofoto 2015 © Provincia autonoma di Trento (CC BY 4.0) · CC-BY-4.0 · terms - Geospatial Information Authority of Japan, seamless aerial photos (全国最新写真) (Japan)
地理院タイル（全国最新写真） / GSI Japan · PDL-1.0 · terms
Offline: allowed with the credit by each licence; not yet in offline packages.
ECMWF open forecast data
Weather forecasts behind the snow estimates.
- Licence
- CC-BY-4.0
- Credit
- Contains modified ECMWF forecast data (2026), licensed under CC BY 4.0.
- Offline
- allowed, with the credit
- Terms
- https://www.ecmwf.int/en/forecasts/datasets/open-data
Copernicus Land Monitoring, high-resolution snow products
Satellite snow observations used to check the snow estimates.
- Licence
- free, with attribution (Copernicus Land Monitoring Service, EEA)
- Credit
- Copernicus Land Monitoring Service
- Offline
- not used offline
- Terms
- https://github.com/eea/clms-hrwsi-api-client-python
Fallbacks, research and snow evidence
These sources are used as a fallback, in research, or as snow evidence beside our own snow estimates. None of them is kept in offline packages.
AWS Terrain Tiles (Mapzen Terrarium)
A fallback for heights in the elevation profile tool, where the main terrain has no data.
- Status
- A fallback in one tool, used only where the main terrain has no data.
- Licence
- mixed open sources (SRTM, GMTED, ETOPO1, national DEMs); attribution per tilezen/joerd
- Credit
- Terrain fallback: Mapzen terrain tiles. SRTM, GMTED2010 and 3DEP terrain data courtesy of the U.S. Geological Survey; ETOPO1 from the U.S. National Oceanic and Atmospheric Administration; EU-DEM produced using Copernicus data and information funded by the European Union; and national sources.
- Terms
- https://github.com/tilezen/joerd/blob/master/docs/attribution.md
Open-Meteo forecast API
Research on the snow model, run by hand.
- Status
- Research only, never called by the site.
- Licence
- CC-BY-4.0 data; the free API is for non-commercial use
- Credit
- Weather data by Open-Meteo.com
- Terms
- https://open-meteo.com/en/terms
NOAA GFS forecast archive
Research comparing weather models for the snow estimates.
- Status
- Research only.
- Licence
- free, with attribution and no endorsement (NOAA open data on AWS)
- Credit
- NOAA GFS
- Terms
- https://registry.opendata.aws/noaa-gfs-bdp-pds/
NASA GIBS: MODIS and VIIRS snow cover
Satellite snow cover used as evidence beside the snow estimates.
- Status
- Used as snow evidence.
- Licence
- NASA Earth science data: open, commercial use allowed, with the GIBS acknowledgement
- Credit
- We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS).
- Terms
- https://nasa-gibs.github.io/gibs-api-docs/access-basics/
Microsoft Planetary Computer (STAC and data API): Sentinel-3 LST, Landsat, Sentinel-1
Satellite observations (surface temperature, Landsat, radar) used as snow evidence.
- Status
- Used as snow evidence.
- Licence
- each dataset's own open licence; the API under Microsoft's Planetary Computer terms
- Credit
- Contains modified Copernicus Sentinel data (year); Landsat imagery courtesy of the U.S. Geological Survey
- Terms
- https://planetarycomputer.microsoft.com/terms
EUMETSAT H SAF H43 snow product
A satellite snow product used as snow evidence.
- Status
- Used as snow evidence.
- Licence
- EUMETSAT data policy: H SAF products free for all users, with the EUMETSAT copyright
- Credit
- Copyright (year) EUMETSAT (H SAF snow product)
- Terms
- https://hsaf.meteoam.it/