Map guide & units
AIS reports update at different times. Report age is the time since the latest position was received.
The vector line shows where a ship would be after the selected number of minutes if its course and speed stay the same.
The map legend shows vessel length colours. Select a ship to read its reported length; an outline without a fill means length is unavailable.
The red and blue outlines identify selected ships A and B. Warning symbols mark projected close approaches; they do not confirm a collision.
SOG (Speed over Ground) is speed over the Earth's surface. COG (Course over Ground) is the direction of travel. MMSI identifies a ship's AIS radio.
NM = nautical miles (1 NM = 1,852 m). kn = knots (1 nautical mile per hour). min = minutes.
The green boundary marks the data subscription area.
Inland water exclusion zone: red areas reduce excessive close-encounter alerts from dense inland and port traffic. Vessels remain visible but are excluded from encounter analysis.
Metric definitions and calculation
Experimental viewer for learning and exploration. Do not use it for navigation or safety decisions. Read the limitations.