Radio Detection and Ranging (RADAR) emits radio waves that detect nearby objects. As we discussed in Chapter 1, The Foundations of Self-Driving Cars, RADAR has been used in the field of autonomous vehicles for many years. RADAR help cars avoid collisions by detecting vehicles in the car's blind spots. RADAR also performs significantly when detecting moving objects. RADAR uses the Doppler effect to measure the distance between objects, as well as their positioning. The Doppler effect measures the change in waves when an object moves closer or further away. You can read more about the Doppler effect at https://en.wikipedia.org/wiki/Doppler_effect.
 RADAR cannot categorize an object, but it is good at detecting its speed and position.
