Once within reach of only the most affluent boaters, marine radar has enjoyed increased popularity due to lower prices, improved designs, and the relatively recent ability to interface with other navigation instruments such as GPS chartplotters and autopilots. Anyone who has found themselves trying to navigate through dense fog or pick out navigation lights against the cluttered background lights ashore can appreciate the additional safety factor that marine radar brings to coastal and offshore navigation. Whether interfaced with other navigation instruments or not, radar is a powerful navigation device that can be used in any situation. How Radar Works

Radar systems are made up of a display and a revolving antenna (or scanner). A stream of short pulse radio waves are transmitted through the antenna and a computer inside the radar receiver measures the time delay of the echo received and calculates the distance to an object or landmass while the rotating scanner determines the bearing. The results are then displayed on the radar screen. Navigating with Radar Boaters equipped with radar can more confidently expand their cruising grounds without feeling completely at the mercy of darkness or the sudden approach of squalls. Radar allows boaters to see landmasses, other vessels, or navigational aids which might ordinarily be hidden from view by darkness or weather conditions. While rain and other precipitation considerably shorten it’s effective operational range, this sensitivity to precipitation also tends to make radar a useful detector of approaching bad weather. Most users operate radar in the Relative Presentation/Heading Up mode because it's the easiest to interpret at a glance. This means that the top of the display screen is always oriented with the bow of the boat, and targets on the screen are always relative to the vessel’s heading.

Another display mode, True Presentation/North Up is oriented like a chart with the boat in the center and the top of the screen pointing north. This makes it possible to observe how navigation aids move on the screen as the boat remains on its intended track. Radars with a north-up mode are usually interfaced with an electronic compass.

The latest and most versatile option is the Course Up mode, which receives navigation input from a GPS or Loran and/or an autopilot (optional). With this mode the top of the screen is relative to the rhumb line course of a selected waypoint. If the heading line of the boat drifts off the rhumb line from either pilot error or current, the resulting movement will show the XTE (cross track error), which can then be easily corrected. This mode is also ideal for avoiding collisions.