To determine collision risk from a moving target on radar which two measurements are most important?

To determine collision risk from a moving target on radar which two measurements are most important?

• A. Bearing to the target and speed
• B. Relative speed and course
• C. Relative bearing and range
• D. Range and color

Answer: (C)

Determining collision risk with a moving target on radar comes down to knowing where the target is relative to your vessel and how that position is changing. The two measurements that give you that information most directly are the target’s relative bearing and its range. Relative bearing tells you the direction of the target off your bow, while range tells you how far away it is. Together, they define the target’s relative position in polar coordinates. By watching how both numbers change over time, you can judge whether the target is converging on your path. If the range is decreasing while the bearing indicates the target is on a line that could intersect your own track, collision risk is present. If the range increases or the bearing shifts away, the risk is lower. Other data like speed or course can help supplement your picture, but they don’t alone give you the immediate sense of where the target is and how its path relates to yours. Color isn’t a relevant factor for collision assessment.

Determining collision risk with a moving target on radar comes down to knowing where the target is relative to your vessel and how that position is changing. The two measurements that give you that information most directly are the target’s relative bearing and its range.

Relative bearing tells you the direction of the target off your bow, while range tells you how far away it is. Together, they define the target’s relative position in polar coordinates. By watching how both numbers change over time, you can judge whether the target is converging on your path. If the range is decreasing while the bearing indicates the target is on a line that could intersect your own track, collision risk is present. If the range increases or the bearing shifts away, the risk is lower.

Other data like speed or course can help supplement your picture, but they don’t alone give you the immediate sense of where the target is and how its path relates to yours. Color isn’t a relevant factor for collision assessment.