If a target's range is decreasing while the relative bearing is constant, what does that indicate?

If a target's range is decreasing while the relative bearing is constant, what does that indicate?

• A. The target is moving away from your vessel
• B. The target is circling around your vessel
• C. The target is moving perpendicular to your vessel
• D. The target is closing in on your vessel along that bearing

Answer: (D)

In polar terms, track the target by its range and bearing. If the range is getting smaller while the bearing stays the same, the target’s motion has a component directly toward your vessel along that fixed line of sight. In other words, the target is moving along the radial line toward you, so you are closing in on it along that bearing. If the bearing stayed the same but the range increased, it would be moving away along that line. If the bearing changed, it would indicate motion off that line (circling or moving perpendicular). So the observed changes indicate the target is closing in along that bearing.

In polar terms, track the target by its range and bearing. If the range is getting smaller while the bearing stays the same, the target’s motion has a component directly toward your vessel along that fixed line of sight. In other words, the target is moving along the radial line toward you, so you are closing in on it along that bearing. If the bearing stayed the same but the range increased, it would be moving away along that line. If the bearing changed, it would indicate motion off that line (circling or moving perpendicular). So the observed changes indicate the target is closing in along that bearing.