What feature can help radar units to filter out noise and improve accuracy?

Digital signal processing is the correct choice because it utilizes algorithms and techniques to manipulate and analyze information in a digital format. This processing allows radar units to effectively filter out background noise that can interfere with accurate speed measurements. By converting the radar signals into a digital format, systems can apply various filters and enhancements to distinguish between relevant signals and noise, leading to improved accuracy in speed detection.

In contrast, while analog signal processing can also be utilized in radar systems, it generally lacks the advanced filtering capabilities found in digital signal processing. Visual identification, while valuable for confirming findings or assessing a situation, does not enhance the radar unit's technical accuracy. Manual calibration is important for ensuring equipment is set correctly but does not improve the inherent noise filtering capabilities of the radar itself. Overall, digital signal processing is essential for maximizing the precision and reliability of radar speed detection systems.