Since 2004, the International Maritime Organization has required all vessels of 300 or more gross tons to carry an AIS transponder, which transponder transmits position, speed and course and other information about the ship. MarineTraffic.com takes that data and plots it on a map. The data is updated every hour — close enough to real-time. Think about it: this is a near-real-time map of every ship on the planet above a certain size. Mind-boggling. Via Cartophilia.

Previously: ESA Maps European Shipping Routes.