Relative / True motion

Question 1

Inputs (heading & speed)
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 1

1. None required
2. Compass & Log, giving heading plus STW
3. Compass & GPS, giving COG plus SOG

Question 2

Assessment of CPA / TCPA
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 2

1. Direct and Easy (OA from start)
2. Resolution required (need to find OA)

3.Resolution required (need to find OA)

Question 3

Assessment of target course, speed and aspect
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 3

1. Resolution required (need to find WA)
2. Direct and easy (WA from start)
3. Resolution required, potentially misleading (WA from start but G/T!)

Question 4

Application
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 4

1. Simple collision avoidance
2. Better for collision avoidance than navigation
3. Better for navigation than for collision avoidance

Question 5

Information displayed relative to
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 5

1. Own vessel
2. The water
3. The ground

Question 6

Moving objects
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 6

1. Move on own respective speeds and courses
2. Move respective to the water (STW and heading)
3. Move respective to the ground (COG and SOG)

Question 7

Fixed objects
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 7

1. Appear to move
2. Appear stationary
3. Appear stationary

Question 8

Stopped vessels
1. Relative motion
2. True motion, Sea stabilised, True vectors
3. True motion, ground stabilised, True vectors

Answer 8

1. Reciprocal of own vessel course and speed
2. Move along a water track
3. Move along a ground track