Source maps in this folder come from the OpenFront map generator assets and are
licensed CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/).
Attribution and share-alike apply if the game is distributed with them.

The Greece, Yugoslavia, USA and Egypt maps (greece/, yugoslavia/, usa/, egypt/)
were built for this game from public data, not from the OpenFront generator:
  * Borders, regions, lakes and spawn towns: Natural Earth 1:10m vectors,
    public domain (https://www.naturalearthdata.com, "Made with Natural Earth").
  * Relief and coastlines: AWS Open Data Terrain Tiles
    (https://registry.opendata.aws/terrain-tiles/), which credit:
      SRTM and GMTED2010 terrain data courtesy of the U.S. Geological Survey;
      Global ETOPO1 terrain data U.S. National Oceanic and Atmospheric
      Administration;
      Europe terrain data produced using Copernicus data and information
      funded by the European Union - EU-DEM layers (Greece and Yugoslavia).
Each of these folders has a SOURCES.txt with the exact layers, projection,
latitude range and where every nation's spawn comes from.

The climate.bin in the Switzerland, Greece, Yugoslavia, USA and Egypt folders
(each map's moisture, which draws its deserts, steppes, grass and forest) is
derived from:
  Beck, H.E., N.E. Zimmermann, T.R. McVicar, N. Vergopolan, A. Berg,
  E.F. Wood: Present and future Koppen-Geiger climate classification maps at
  1-km resolution, Scientific Data 5, 180214 (2018),
  doi:10.1038/sdata.2018.214; data doi:10.6084/m9.figshare.6396959.
  Licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/);
  attribution required. Changed: the climate classes were turned into
  moisture values, reprojected onto each map's grid and smoothed (the Climate
  section of each SOURCES.txt gives the table and the method).

The colour.png in the Egypt folder (the land's real colours, which the game
draws under its own light and relief when Settings' Real map colours is on) is
derived from NASA's Blue Marble Next Generation (Reto Stockli, NASA Earth
Observatory; 500 m, 2004), public domain (NASA imagery is not copyrighted;
credit: NASA Earth Observatory), fetched as tiles of the WMTS layer
BlueMarble_NextGeneration from NASA's Global Imagery Browse Services
(https://gibs.earthdata.nasa.gov). 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). Changed: reprojected onto
the map's grid, its water left out and filled from the nearest land (the
Colour section of SOURCES.txt gives the method).
Egypt's Lake Nasser is SRTM's flattened water surface from the same AWS
Terrain Tiles as its relief.