J. B. Crawford’s long essay on geodesy looks at the challenge of synchronizing the datums created by the various national surveys, giving the reader sufficient background technical information for understanding the culmination of those efforts: the North Atlantic Tie, by which the North American, British and European datums (NAD27, OSGB36 and ED50) were linked together, and the eventual creation of WGS60—just in time for satellite observations to take over. Worth a read.