This effect can be observed when a person shouts in a valley. The sound waves travel to the nearby mountains and get reflected. The person thus hears back his own voice. The time taken by the sound waves to return back depends upon the distance between the persons and the mountains. The similar concept is applied in RADAR. Here radio waves are emitted by the RADAR which travel in all directions. If an object comes in the way of these waves they get reflected back with the speed of light and detected by the RADAR. By knowing the time elapsed between sending and receiving back the waves, the position of the object can be determined by calculating the distance the wave has travelled.
Now in order to calculate the speed of an object the concept of Doppler shift plays its role. When a wave is reflected by a moving object its nature depends upon the movement of that object. If the object is moving towards the source of the wave, then the pitch of the wave will be higher than if it is moving away from it. This can be observed in case of a car blowing its horn. When a moving car approaches a person the horn seems to be louder and when it moves away it become s somewhat fainter. Knowing the pitch of the sound wave the speed of the car can be detected. This principle is applied in case of RADAR where a radio wave is used instead of a sound wave. The pitch of the reflected radio wave determines the speed and the direction of motion of the object. Combining the Echo and Doppler Shift, we can exactly determine the position, speed and direction of motion of an object in the sea with the help of a Navigational RADAR.
Components of Marine Navigational RADAR
There are five main components of a Marine Navigational RADAR.
A transmitter is a device which transmits radio waves into the air. These waves are generated inside the RADAR.
It allows waves to be omitted as pulses (Integrated Publishing, n.d.).
An antenna is used to give direction to the radio waves being transmitted. These waves are sent as 'beams'. The antenna is always in rotating condition so that the whole of the area is covered.
It receives back the reflected waves from the objects and converts the information into usable data (Integrated Publishing, n.d.).
It is a device on which the received information is plotted. It shows the position of the object in the form of a mark on a screen.
The standard indicator that is used mainly is known as Plan Position Indicator (PPI). It