Ever wonder how that radar unit in you dashboard does its job?

Consult Chapman Piloting & Seamanship and you find that radar (which is actually an acronym, short for Radio Detection and Ranging) measures distance by sending out radio pulses, which strike objects around the boat – vessels, land, icebergs, whatever. The unit then measures the time it takes for these pulses to reflect back, and that information is processed and translated into the video image we all know so well.

While radar can see in the dark and in bad weather, it is limited to line-of-sight operation, much like a television remote control. It cannot see through land or around corners. A radar unit's range is determined largely by the height of its antenna, with the unit's power level and the size of the antenna also playing a role.

The antenna, usually mounted on a pilothouse roof or mast, should not be located anywhere where it can pick up interference from other systems on your boat – including the crew. As the book says, "The beam of energy should pass well clear of the heads and bodies of persons on board"¦."

– Theodore J. Sawchuck