Icons
The icons on the map are used to categorized the vessels based on their basic type (Cargo,Tanker,Tug,etc)
The colors are
Unknown Vessel Type
Tug, Pilot
High Speed
Passenger
Cargo
Tanker
Fishing
Yachts and Other
Air Craft
Base Stations
Navigation Aid
Also each vessel's icon has a small color bar that indicates when the last position was received
(Green) Received < 5m ago
(Orange) Received >5m and < 15m ago
(Red) Received > 15m ago
Moving VS Not moving
Vessel is moving
Vessel is NOT moving