The 'source' documents for this project are the .json files in sources. To add
a new imagery source, add a new file to this directory.
The format for sources is formally described in schema.json and can be checked
with make check.
Specifying reduced accuracy dates is complex. For simplicity, the schema allows
a subset of ISO 8601 defined in RFC 3339
except that a reduced precision date is allowed. For example, 2013-04-15T14:02:54.05+00:00
is a fully specified ISO 8601 date-time, 2013-04-15 could be used for just the date,
or 2013-04 for just the month, 2013 for just the year.
Implementations may round down the end date (e.g. consider 2013 the same as the
start of 2013 so to specify imagery taken sometime in 2013, use "start_date": "2013",
"end_date": "2014".
After you've made a modification, run make to generate imagery.xml, imagery.json,
and imagery.geojson. Generating these files requires Python.