Data Sources

Data Sources

Arnis combines quite a few open datasets. OpenStreetMap is the base for everything man-made, and the rest fills in the terrain, what the ground looks like and where OSM has gaps. This page lists every source, when it's used and where it's cached.

Source	What it gives Arnis	When
OpenStreetMap	buildings, roads, railways, water, land use, almost every object	always on Earth (except below scale 0.3)
Overture Maps	extra building footprints and building heights	Additional Buildings, on by default
Mapterhorn	terrain height	default on Earth
AWS Terrain Tiles	terrain height (older, coarser)	fallback, or Legacy terrain
NASA PDS	terrain height of the Moon and Mars	Moon and Mars worlds
ESA WorldCover	land cover: forest, fields, built-up, water and so on	always on Earth
Meta/WRI canopy height	where trees stand and how tall they are	Real Tree Cover, on by default
Köppen climate, RESOLVE ecoregions	climate, biomes, plant and tree species	always on Earth (bundled, no download)
Mapillary	street-level photos for building facades	only with a token
3DMR, Wikimedia Commons	3D models of landmarks	3D Models & Props, on by default
Nominatim	city search and area names	GUI search, world names

OpenStreetMap

OpenStreetMap is a free map of the world that anyone can edit. It's the reason Arnis exists at all: services like Google Maps don't give their data out like this.

The Arnis tile archive

By default, Arnis doesn't query OSM live. Instead it reads from its own tile archive at https://tiles.arnisproject.com/v1: one PMTiles file per continent, baked from the OSM planet file by a separate tool (arnis-tiles). The archive is split into zoom-13 tiles (about 5 km across), and a run only downloads the tiles its area covers, using HTTP range requests. That's a lot faster and more reliable than Overpass, and it doesn't put load on public OSM servers.

This means the data is as fresh as the last bake, not live. If you fix something on openstreetmap.org, it shows up in Arnis once the archive has been rebuilt.

The archive serves areas up to 25,000 km² at scale 1 (smaller at a larger scale).

Overpass fallback

If the tile archive isn't reachable or has no data for the area, Arnis falls back to the Overpass API. It only uses its own instance at api.arnismc.com. Public instances were taken out because Arnis' traffic was too much for them (see #1347). --no-tile-archive uses Overpass directly.

Local files

On the command line, --file reads OSM data from a local .osm/.xml file or an Overpass JSON file instead of downloading anything. Without --bbox, the area is taken from the file. PBF files aren't supported.

Overture Maps

Overture Maps publishes building footprints from several sources, including machine learning detection from satellite images (Microsoft, Google Open Buildings, Esri). In places where few buildings are mapped in OSM (rural Africa or parts of Asia for example), this helps a lot.

Arnis uses it in two ways:

• Missing buildings: footprints that don't come from OSM and don't sit inside an OSM building are added.
• Heights: OSM buildings without height or building:levels get the height Overture has for them.

The data is read either from Overture's PMTiles vector tiles or from its GeoParquet files (--overture-source), from the newest release that's online. Satellite detection isn't perfect, so now and then a building shows up that doesn't exist. Turn off Additional Buildings if that bothers you.

Elevation

The elevation grid has one sample per block. How it's turned into terrain is explained on the Ground Generation page.

• Mapterhorn (default): a global terrain dataset built from the Copernicus GLO-30 model, plus national high resolution elevation and LiDAR data in many countries, partly down to 1 m. Arnis picks the zoom level from the size of a block in the world, so at scale 1 in a country with LiDAR you get very detailed terrain, and a large area at a low scale downloads far less.
• AWS Terrain Tiles (about 30 m): the older source. Arnis falls back to it on its own if Mapterhorn fails or returns mostly holes. Legacy terrain (--aws-only-elevation) uses only AWS, which helps when Mapterhorn downloads get stuck. Mapterhorn is served through Cloudflare, which is throttled by some internet providers.
• NASA PDS: LRO LOLA for the Moon and MGS MOLA for Mars, both at 128 pixels per degree. Only a window of the global files is read, again with range requests.

If no elevation source works, the world is generated on flat ground.

Land cover

ESA WorldCover 2021 is a land cover map from Sentinel satellite images at 10 m resolution, with classes like tree cover, shrubland, grassland, cropland, built-up, bare ground, snow and ice, water, wetland, mangroves and moss. It covers latitudes from 60° south to 84° north.

It's used on every Earth world, also on flat ones, and decides what the ground is made of wherever OSM doesn't say. It's also where the sea comes from: Arnis doesn't use OSM coastlines, the land cover water is more reliable for that. OSM then corrects the land cover where they disagree (see Ground Generation). If it can't be downloaded, Arnis uses default ground blocks.

Canopy height

The Meta and World Resources Institute canopy height map estimates the height of the tree canopy worldwide at about 1 m resolution. Arnis uses it to place trees where real ones stand, at about their real height (Real Tree Cover, --canopy-height). Anything from 3 m up counts as a tree. If it's off or can't be downloaded, trees are placed from the land cover instead.

Climate and ecoregions

Two world grids are compiled into Arnis, so they don't need a download:

• Köppen-Geiger climate (Beck et al. 2023, 1991 to 2020) at 0.1°: decides arid and polar ground, biomes and how dense plants grow.
• RESOLVE Ecoregions 2017 (Dinerstein et al.) at one arc-minute: decides biomes, which plants and tree species grow and whether palms belong there.

Mapillary

Mapillary street-level photos are used for the Building Facades if you add a token. Arnis downloads the photo metadata, their 3D reconstructions and thumbnails around your area. The imagery is CC BY-SA 4.0 and every photo that's used is credited.

3D models

• 3DMR: elements with a 3dmr=* tag get their model from the 3D Model Repository.
• Wikimedia Commons: landmarks with a wikidata=* tag that's in a bundled index get their 3D model from Commons. There's no live Wikidata query, the index is part of Arnis, and it only includes permissively licensed models (CC0, public domain, CC BY).
• arnismc.com: a few generic models (e.g. for stadiums) and curated landmark models are hosted by Arnis itself.

See Element Processors for how they're placed.

Nominatim

The city search in the GUI uses OpenStreetMap's Nominatim. It's also used for reverse geocoding, to give worlds a name like "Arnis World 3: Munich" and for titles in the gameplay extras.

Other connections

• Update check: Arnis asks the GitHub API whether there's a newer release.
• Crash reports: only if you agreed to them, see the FAQ.
• Map backgrounds in the GUI (OpenStreetMap, Esri satellite, OpenTopoMap, Stadia, OpenFreeMap and the Moon and Mars maps) are only for picking your area and never end up in the world.

Caching

Everything Arnis downloads is cached, so generating the same area again (or a neighbouring one) is much faster. The caches live in your system's cache folder:

System	Cache folder
Windows	%LOCALAPPDATA%
macOS	~/Library/Caches
Linux	~/.cache

In there:

Folder	Contents	Cleaned up
arnis-tile-cache/	elevation tiles (Mapterhorn, AWS, Moon, Mars) and Mapillary imagery and facades	files older than 30 days, checked once a day at startup
arnis-landcover-cache/	ESA WorldCover	never
arnis-canopy-cache/	canopy height	row data after 30 days
arnis-overture-cache/	Overture buildings, per release	when a newer release is used
arnis/osm-tiles/	the OSM tile archive	when an archive is replaced
arnis/3dmr/, arnis/wikidata_models/, arnis/custom_models/	3D models	never

Clear Cache under Settings > Application empties all of them. It can't run while a generation is running.

Licenses and credits

The full list of sources, authors and licenses is in the app under License and Credits, and in src/gui/js/license.js in the repository. The credits for the 3D models and Mapillary photos used in a run are added there too. If you turn on the Arnis pause menu, the world also carries its data credits.

If you share worlds or screenshots, please keep the attribution, at least "© OpenStreetMap contributors".