Final answer:
In radar terminology, the unwanted echoes are referred to as clutter. Clutter includes reflections from objects such as waves, land, or other vessels that are not the primary targets of interest.
Step-by-step explanation:
The unwanted echoes referred to in the scenario with multiple radar targets at different ranges are commonly known as clutter. Clutter in the context of radar refers to radar reflections that are not of interest to the observer and can potentially interfere with the detection and accurate location of desired targets. In this specific situation, the radar targets to the starboard side are the unwanted echoes, which could be caused by various objects such as waves, land masses, or other vessels that the radar system picks up inadvertently.
Radar systems use the reflection of radio waves to determine the distance and location of objects by measuring the round-trip time it takes for a radar pulse to return after hitting an object. Clutter can be minimized or filtered through various techniques to ensure more accurate readings for navigation and safety purposes.