With bearings rounded to the degree the CPA is very sensitive to the echoes chosen: here the first and last echoes are used, giving 0.55 M; on a hand plot you may also read about 0.4 M. The target is heading the same way but slower: you overtake it and see its stern light, which is white.
Head Up display, 10-mile range scale. Your ship steers 355° at 20 knots. A target appears at 1110 at 9.0 M, relative bearing 008°; at 1116 at 8.0 M, 009°; at 1122 at 7.0 M, 009°. Is there a risk of collision? What are the target's course and speed?
- Display
- Head Up, own heading 355°, 20 kn
- Echo at 1110
- 9.0 NM, 008° relative
- Echo at 1116
- 8.0 NM, 009° relative
- Echo at 1122
- 7.0 NM, 009° relative
Solution worked out by us from the course material: to be checked by the instructor.