ARPA

Question 1

What are 8 IMO requirements for ARPA?

Answer 1

1. ARPA must be able to track at least 20 targets automatically and 10 manually.
2. ARPA should be able to display history - minimum of 4 positions over at least 8 minutes
3. ARPA should indicate lost targets
4. ARPA should have a trial manoeuvre function
5. Range and bearing info must be quickly available for objects appearing on an ARPA display.
6. Data requirements are Target Range, Bearing, Predicted CPA, Predicted TCPA, True Course and True Speed
7. ARPA data should be clearly visible to more than one person on the bridge during the day and at night.
8. ARPA must provide laid down accuracy within 1 and 3 minutes.

Question 2

What are some ARPA alarms?

Answer 2

1. A selected target breaches user defined CPA/TCPA limits
2. A tracked target is lost
3. An input failure (Gyro, speed etc.)
4. A target enters the guard zone (that isn’t already being tracked)
5. Picture freeze

Question 3

What is the order of information from ARPA?

Answer 3

1. Target range, Bearing, Predicted CPA, Predicted TCPA, True course, True speed

Question 4

Name some problems with ARPA (6 factors)

Answer 4

1. ARPA will not question any faulty data inputs from own vessel i.e speed, heading - this will change the vector triangle calculation therefore giving potentially dangerous incorrect data
2. Range and bearing discrimination still exists
3. Ice, small targets and floating objects may not appear and remain undetected
4. False echoes may give rise to false situations
5. Lost targets, in sea state or rain banks
6. Target swap (when a target plotted by an ARPA loses its ‘tag’ to another passing vessel or static radar target)
7. Over-reliance in the technology