Where the data comes from

Every measurement in the Atlas was published by somebody else first. These are the 21 sources whose mapping was harvested, reconciled into one schema and — where their terms permit redistribution — republished here with the citation of the map each row came from.

Sources whose terms do not permit redistribution are counted in the record of each compile but never shipped. "Convention stated" is the share of a source's records that declare their own azimuth convention in the published data rather than leaving it to be inferred.