Circa: processed historical-basemaps outlines
==============================================

historical-basemaps-processed.geojson.gz holds 10,308 historical region outlines that Circa
(samarchive.com/circa) uses to choose the region a click selects. They are derived from
historical-basemaps by Andre Ourednik and contributors:

  https://github.com/aourednik/historical-basemaps
  at commit da7a4b735ecef70aebdc9c73e409d8a2500d50f3

historical-basemaps is licensed under the GNU General Public License, version 3. This derived data is
released under the same license; the full text is in GPL-3.0.txt next to this file.

What was changed from the source files:
- Each world_<year>.geojson snapshot was given the years closest to it (from_year and to_year, historical
  numbering: 1 BCE is -1, and there is no year 0).
- Features without a name were dropped. One name mangled in the source, "M?ori" in world_1878, was
  corrected to "Māori", the spelling of the neighbouring snapshots.
- Names the site's owner struck were dropped: see etl/struck-names.json in the source code.
- Shapes were simplified at 0.02 degrees and coordinates rounded to 3 decimal places.

Each feature's properties are name, from_year and to_year. The outlines are approximate and are not maps
of record. The code that made this file is the etl/ folder of Circa's source repository.