Boatnerd

Welcome to Great Lakes & Seaway Shipping Online’s Vessel Passage Maps. These AIS-derived maps show current vessel locations throughout the Great Lakes. The following are frequently asked questions about the maps

The Automatic Identification System (AIS) is a radio-based system used by ships and vessel traffic services to track the location of ships. Its primary purpose is collision avoidance. AIS uses digital radio signals transmitted over VHF maritime channels 87B (161.975 MHz) and 88B (162.025 MHz) to broadcast information about a ship including its name, position, speed, course, dimensions, destination, and status. The use of AIS is mandated for international ships over 300 gross tons under the International Convention for the Safety of Life at Sea (SOLAS). US and Canadian laws require its eventual use on the Great Lakes for ships over a certain tonnage. Some vessels, such as ferries operating on a constant route, are exempted.