The files in this directory are extracts derived from OpenStreetMap data,
made available under the Open Database License (ODbL) 1.0:
https://opendatacommons.org/licenses/odbl/1-0/

© OpenStreetMap contributors — https://www.openstreetmap.org/copyright

- land.pmtiles      Coastline/land polygons (via osmdata.openstreetmap.de),
                    tiled with tippecanoe. Vector tiles, PMTiles v3 format.
- land_mask.png     14400x7200 1-bit land/water grid rendered from the
                    simplified land polygons (EPSG:4326, lon -180..180 west
                    to east, lat 90..-90 top to bottom; white = land).
- tz_index.png      3600x1800 RGB index of IANA time-zone regions built with
                    timezone-boundary-builder data (also OSM-derived); pixel
                    color indexes into tz_zones.json.
- tz_zones.json     IANA zone identifiers referenced by tz_index.png.

These are byte-identical copies of the database files shipped inside the
MarCast iOS app, published to satisfy ODbL share-alike (sections 4.6/4.7).