Switzerland map — data sources and attribution
==============================================

Built from Swiss federal geodata published by the Federal Office of Topography
swisstopo on https://data.geo.admin.ch. swisstopo free geodata may be used,
redistributed, modified and used commercially, but SOURCE ATTRIBUTION IS
MANDATORY:

    (c) Bundesamt fuer Landestopografie swisstopo

Datasets used
-------------
Elevation   ch.swisstopo.swissaltiregio (swissALTI Regio, 10 m national DEM)
            https://data.geo.admin.ch/ch.swisstopo.swissaltiregio/swissaltiregio/swissaltiregio_2056_5728.tif
            Read as a Cloud-Optimized BigTIFF; overview level 2 (80 m) only.
            swissALTIRegio merges foreign DEMs outside Switzerland, which must
            be credited as well:
              TINITALY / INGV (Italy), geoland.at (Austria), RGE ALTI / IGN
              (France), DGM1 Bayern and the Baden-Wuerttemberg / EU-DEM data
              (Germany).

Borders     ch.swisstopo.swissboundaries3d, release 2026-01
            https://data.geo.admin.ch/ch.swisstopo.swissboundaries3d/swissboundaries3d_2026-01/swissboundaries3d_2026-01_2056_5728.shp.zip
            Layers: TLM_LANDESGEBIET (national outline = the coastline),
            TLM_KANTONSGEBIET (the 26 cantons), TLM_HOHEITSGEBIET
            (municipalities with population, for the canton spawn points).

Lakes       ch.swisstopo.swisstlmregio, release 2025 (GeoPackage)
            https://data.geo.admin.ch/ch.swisstopo.swisstlmregio/swisstlmregio_2025/swisstlmregio_2025_2056.gpkg.zip
            Layer tlmregio_hydrography_lake.

Geometry
--------
Projection      EPSG:2056 (CH1903+ / LV95), the official Swiss projection --
                conformal and metric, so no latitude aspect correction is used.
Grid            2000 x 1264 tiles at 175 m/tile (350.0 x 221.2 km)
Origin          tile (x,y) covers E = 2484634 + 175*x, N = 1296201 - 175*y
Elevation curve magnitude = round(unsharp(elevation) / 120 m), clamped 0..31,
                where unsharp = e + 2*(e - gaussian(e, sigma = 2 tiles)).
                Terrain band cuts therefore fall at 1200 m (Plains/Highland)
                and 2400 m (Highland/Mountain).
Latitude        row 0 = 47.8 N, last row = 45.8 N (crates/of_app/src/view.rs).

Lake policy     A lake under ~1.2 km2 is not represented, at any resolution
                (40 tiles at full res, 10 at 4x, 3 at 16x); such bodies are
                filled back to land at the surrounding ground height. Applied
                to map4x.bin/map16x.bin after the plurality-vote downsample,
                which otherwise left 46 and 40 disconnected one- and two-tile
                fragments of the narrow arms of real lakes.

Climate (climate.bin)
---------------------
Source      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: figshare, doi:10.6084/m9.figshare.6396959 (Beck_KG_V1.zip, no login),
            Beck_KG_V1_present_0p0083.tif (present day, 1980-2016, ~1 km).
            Licence CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/):
            attribution required; the classes were turned into moisture values
            and reprojected (changes made).
Grid        the map16x grid, 500 x 316: one byte per 16x tile, 0 = driest, 255 = wettest,
            on the terrain shader's own moisture scale (x 255).
Method      each Koppen class -> a moisture (table below); reprojected with the map's
            projection, each 16x tile the area average of the 1 km cells in it; the sea
            and the neighbours (water on this map) take the nearest own land's value;
            Gaussian smoothing, sigma 8 km (11.4 tiles of 0.70 km).
Classes     BWh, BWk 0.06; BSh, BSk 0.28; Csa 0.34; Dsa 0.40; Csb, Csc, Dsb 0.46;
            Dsc, Dsd 0.48; Aw, ET, EF 0.50; Cwa, Cwb, Cwc, Dwa, Dfa 0.52;
            Cfb, Cfc, Dwb, Dwc, Dwd, Dfb 0.53; Dfc, Dfd 0.58; Cfa 0.60; Am 0.66; Af 0.76.
            The shader's temperate ladder: desert under 0.22, steppe to 0.33, grass
            to 0.56, forest above; in hot country savanna from 0.24, grass from 0.45,
            jungle above 0.56. Tundra and snow come from the temperature.
Land        the largest classes by 16x land tile: Dfb 48%, ET 23%, Dfc 18%, Cfb 10%.
            As the temperate ladder reads it: desert 0.0%, steppe 0.0%,
            grass 99.4%, forest 0.6% (before the shader's noise, heat
            and altitude).