Boatnerd Discussion Forum

One would be a 3 cm and the other would be a 10 cm. Each has its advantages. 3 cm can paint a more accurate coastline although it is more affected by precipitation. A 10 cm gives much less accuracy of shorelines but is better in precipitation. The cm refers to the wavelength of the signal transmitted in centimeters.

Modern radar units are versatile and flexible tools. Having more than one unit allows the bridge crew to simultaneously scan at different ranges and for different things. For instance while operating in an area where there may be dangerous debris, deadheads, glacial ice, or lots of small craft, the bridge crew might use one radar set at a very close range and tuned correctly to scan for small objects, and use the other radar to scan farther away to pick up the shoreline and other large vessels.

Each radar unit has particular strengths and weaknesses, so multiple units can compliment each other in that way as well.

I believe one is usually for river navigation (more sensitive - higher detail) than a standard broad coverage radar.

I notice many ships have two radars turning atop the wheelhouse. Sometimes one is higher then the other and/or one is bigger then the other. Is one just a backup or do they serve different purposes? Thanks!