Geography data

Descry's peak, pass, saddle, and ridge feature tiles are a derivative database of OpenStreetMap data, © OpenStreetMap contributors. The complete derivative database is publicly available, in the same form the app downloads, under the Open Database License (ODbL) 1.0.

Getting the data

Everything is served over plain HTTPS from https://data.getdescry.com/v2, with no authentication:

• index.json lists every published region (regionId, name, bounding box).
• regions/<regionId>/manifest.json lists every tile in that region, with its kind, grid index, size, and SHA-256.
• Each manifest entry of kind feature with grid index (tileX, tileY) is served at tiles/features/<tileX>_<tileY>.tfea. Terrain tiles are at tiles/dem/<tileX>_<tileY>.tdem and tiles/lod/<tileX>_<tileY>.tdel.
• ATTRIBUTION.txt carries the notices below.

Together, the feature tiles of all regions listed in the index are the entire derivative database. The format specification below documents each record: coordinates, elevation, kind, flags, importance score, and name.

Licenses

• Feature tiles (.tfea): derived from OpenStreetMap, © OpenStreetMap contributors, and made available under the ODbL 1.0. If you publicly use or redistribute this database, or a work produced from it, the ODbL's attribution and share-alike terms apply to you.
• Terrain tiles (.tdem, .tdel): produced using Copernicus WorldDEM-30, © DLR/Airbus DS, provided under Copernicus by the European Union and ESA, and subject to the Copernicus DEM terms. They contain no OpenStreetMap data.

All integers and floats are little-endian, with no padding. Coordinates are WGS84 decimal degrees; elevations are meters above the EGM2008 geoid.

Tile grid

Each .tfea file covers one 0.25° × 0.25° cell, indexed from the south-west corner of the world: tileX = floor((lon + 180) / 0.25), tileY = floor((lat + 90) / 0.25). Every feature lies inside its own cell, so each feature appears in exactly one tile.

File layout

A 20-byte header, followed by count records packed back to back.

Offset	Type	Field
0	4 bytes	magic, ASCII TFEA
4	u16	format version (2)
6	u16	reserved (0)
8	i32	tileX
12	i32	tileY
16	u32	count, number of records

Each record is 26 bytes plus the length of its name:

Offset	Type	Field
0	f64	latitude
8	f64	longitude
16	i16	elevation, meters
18	u8	kind: 0 peak, 1 saddle, 2 pass, 3 ridge point
19	u8	flags, see below
20	f32	importance score, higher is more notable
24	u16	nameLen, 0 if unnamed
26	nameLen bytes	name, UTF-8

Flags: bit 0 means the feature has an OpenStreetMap name; bit 1 means OpenStreetMap had no usable elevation, so it was sampled from the terrain model; bit 2 means the OpenStreetMap elevation and the terrain model disagree by more than 30 m. Records are sorted by descending score.

Manifests

Each entry in a region's manifest.json has a kind (feature, dem, or coarse), a tileX and tileY, the file's size in bytes, and a sha256 of the file as served. Neighbouring regions can share tiles.