It's a classic scene from World War II movies. The captain and his executive officer are hunched over the radar operator, the three of them staring intently at a glowing screen. A radar beam circles the blank screen once, twice, a third time. Then, suddenly, the screen lights up. "There he is," the captain exclaims. The captain turns and, with fire in his eyes, shouts, "we've got him this time! Battle stations!"
It's an exciting scene that pumps the adrenaline every time. It is also completely wrong.
Anyone who has spent any time staring into with a radar screen quickly discovers that there is a lot of information being presented – some of it useful, most of it not. According to the Rules of the Road, a mariner has to consider the limitations of his radar unit when making decisions, but most radar units don't include a list of these limitations in the owner's manual. A radar class will cover these limits, but there is no requirement for recreational boat owners to take such a class.
The limitations are sea and air clutter, minimum and maximum range resolutions, beam width and beam height. Although these may sound technical, the basic concepts are fairly simple – even intuitive.
