terrain.party README
====================

Hooray! You've exported some stuff from terrain.party v1.2!

If you should want to export this again for any reason:
  http://terrain.party/api/export?name=GardenValley&box=-120.679709,38.908745,-120.910595,38.729082

Now: what did you get?


Height Maps
-----------

  * GardenValley Height Map (ASTER 30m).png

    ASTER is the most recent public survey of elevation on Earth. It has high
    coverage and high (~30m) resolution. However, the instrument can get
    confused by high concentraions of clouds and mountains, creating gaps in
    the data that need to be repaired by hand.
    http://asterweb.jpl.nasa.gov/gdem.asp


  * GardenValley Height Map (Merged).png

[!] If you look at one height map, look at this one. [!]

    This is a mix of ASTER (~30m), USGS NED (~10m), and SRTM30+ (~900m). It
    provides good global elevation data (ASTER) and better US elevation data
    (USGS NED) with hole-filling and bathymetry from SRTM30+.


  * GardenValley Height Map (SRTM3 v4.1).png

    SRTM data was originally provided by the Shuttle Radar Topography Mission
    but SRTM3 v4.1 is the result of considerable effort from CGIAR-CSI. It has
    a ~30m resolution in the US and a ~90m resolution elsewhere.
    http://www.cgiar-csi.org/data/srtm-90m-digital-elevation-database-v4-1


  * GardenValley Height Map (SRTM30 Plus).png

    SRTM30+ data is very, very coarse (~900m). This might be useful if you'd
    like to follow the general contours of the land (and seafloor!) without
    having every single contour. (But really, it's here because... why not?)
    http://topex.ucsd.edu/WWW_html/srtm30_plus.html


  * GardenValley Height Map (USGS NED 10m).png

    The National Elevation Dataset is provided by the US Geological Survey. It
    has a ~10m resoution throughout the United States, and it generally has
    extremely good quality.
    http://ned.usgs.gov/


Elevation Adjustment
--------------------

The original elevation models for this area contained elevations ranging from
200 through 1401 meters.

These elevation values need to get transformed into a grayscale images. This
section describes how that translation was done in this particular case.

(The game isn't yet released, so what follows is a guess, but I think it's a
pretty good guess. If this turns out to be wrong, please use the link above to
re-export this data once we figure out what the deal is.)

Cities: Skylines supports terrain from 0m to 1024m. It represents elevations as
16-bit unsigned integers, which can be read directly from 16-bit height maps.
Each level therefore corresponds to 1/64th of a meter: 0 is 0m, 64 is 1m, etc.
Cities: Skylines maps default to having sea level at 40m, with typical terrain
starting at 60m.

These heightmaps were adjusted such that 200m (actual) is equal to 40m in
game. All other elevations are relative to that.

Again, the lowest point in these height maps is now 40m in game; all other
terrain is even higher. You will likely want to adjust the water level as a
result.

One other gotcha -- the area selected for export here has an exceptionally large
range of elevations. These real-world elevations were compressed into the
available range of in-game elevations, which will makes things appear flatter
than they are in reality. This is unfortunate, but there aren't a lot of great
alternatives; C:S only supports 1024m of elevations in total.


Enjoy!
http://terrain.party/
