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# How Does Marine RADAR Work?

by Steve Smith

### Echoes and Pings

A marine RADAR is a ranging and detection system that picks up signals from objects several hundred feet or several miles away from your boat. The RADAR system sends out a signal in the form of a sound wave. This pulse is sent out from the RADAR dish on top of your boat. When the signal is reflected by an object, the RADAR computer determines how far away it is and where it is located. It requires two types of readings for this to occur.

### Distance

Let's say that a boat is a mile off your starboard bow. The RADAR signal is sent out and comes in contact with this boat, it then bounces off the boat and registers on the receiver. The receiver sends this signal to the computer, which measures the time it took for the signal to reflect back. If the computer knows how fast the beam is traveling, the speed of the reflection can be applied to a formula to find the distance.

### Position

The RADAR unit can determines a boat's position because the computer keeps track of where the RADAR unit is located when it receives a ping. The unit is constantly spinning on top of your boat, so the RADAR beam is actually being swept across the water all around you. When a ping registers, the computer can tell where the object is located by the position of the RADAR unit. If the ping registers when the unit is facing 90 degrees to the south, then it plots that object 90 degrees to the south on the screen.