Furuno FEA-2807 Operator's Manual page 152

8. Vector Chart Material
Linked objects
Often a group of chart objects are linked together. The most common example of this practice is a beacon or buoy,
in which the body and the top mark are defined separately. Another example is lights and recommended track. Still
another example is measurement mile. There are also other similar cases.
Body and top hat of a beacon or buoy
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