Radar and ARPA Part 2

Question 1

Use a sketch of a radar display to show how a Parallel Index line can be used to monitor the track of a vessel.

Answer 1

Question 2

Parallel index lines - Explain how the OOW would regain track and then remain on track

Answer 2

Alter course (into the tide) until the vessel regains track with the PI off the headland.

Adjust heading to make good the required ground track.

Question 3

What should be checked when parallel indexing and position fixing?

Answer 3

• Heading marker alignment
• Gyro error and gyro input
• Alignment of radar with gyro input
• Positive identification of
  navigational objects of interest

Question 4

What is a SART used for and what type of radar would you expect to see its transmissions?

Answer 4

A Search and Rescue Transponder is used for locating a casualty.

It can be seen on a 3cm (X-band) radar

Question 5

Describe the use of a True Vector

Answer 5

It indicates the direction a target is moving in (heading on a sea stabilised radar)

Question 6

Describe the use of a Relative Vector

Answer 6

It gives indication of risk of collision if in the direction of own ship

Question 7

List the five factors to take into account when setting the CPA/TCPA alarm on the radar?

Answer 7

The state of visibility
Traffic density
Manoeuvrability of the vessel
Proximity of navigational hazards Master’s standing orders

Question 8

How many targets can the OOW expect to be able to track at one time?

Answer 8

Between 20 and 40 depending on the size of vessel

Question 9

List, in order, the six pieces of information ARPA is required to give about a target

Answer 9

Present Range
Present Bearing
Predicted CPA
Predicted TCPA
Calculated True course Calculated True speed

Question 10

After acquiring a target how long should the OOW wait before being given reliable information based
on steady state tracking?

Answer 10

3 minutes

Question 11

Explain what can happen when two acquired targets are moving close to each other on the display and what action the OOW should take.

Answer 11

As two targets get close to one another their tracking gates may overlap.

The radar may get confused and stop tracking one target with the other one given its vector

One vector should be deleted from this target

The target should be re-acquired