CMRT CMRT Target Tracking & ARPA 2 — Questions and Answers
Question 1: What initial data does ARPA require from its own-ship sensors to compute accurate target tracks?
- Own ship's speed and heading (Correct answer)
- Only the compass heading
- Only the GPS position
- Target's AIS data
Correct answer: Own ship's speed and heading
ARPA needs own-ship heading (from gyrocompass) and speed (from log or GPS) to resolve relative target motion into true target motion.
Question 2: How long does IMO performance standard require an ARPA to establish a steady-state track on a new target?
- Within 1 minute for 10 knots and within 3 minutes for all targets (Correct answer)
- Within 30 seconds for all targets
- Within 5 minutes regardless of target speed
- Within 10 radar scans
Correct answer: Within 1 minute for 10 knots and within 3 minutes for all targets
IMO standards require ARPA to display a target's predicted motion within 1 minute for targets on steady courses at up to 10 knots, and within 3 minutes for all other targets.
Question 3: A technician notices ARPA vectors consistently point in incorrect directions even though targets are correctly positioned. Which sensor is most likely faulty?
- Gyrocompass heading sensor (Correct answer)
- Radar transceiver
- Log speed sensor
- GPS receiver
Correct answer: Gyrocompass heading sensor
Incorrect vector directions with correct target positions indicate a bad heading input, because the ARPA uses heading to convert relative to true bearings.
Question 4: What does 'acquisition' mean in the context of ARPA?
- The process of selecting a radar return and beginning to track it (Correct answer)
- The procedure for purchasing a new radar system
- Locking the radar beam onto a satellite signal
- Storing a target's data in long-term memory
Correct answer: The process of selecting a radar return and beginning to track it
Acquisition is the process by which the ARPA selects a radar echo (manually or automatically) and initiates a tracking algorithm on it.
Question 5: In a sea-stabilized ARPA display, a target's vector shows the target moving directly toward your vessel. What does this indicate?
- The target is on a collision course with zero CPA (Correct answer)
- The target is maneuvering to avoid your vessel
- The target is stopped in the water
- The target's track data is corrupted
Correct answer: The target is on a collision course with zero CPA
A true vector pointing directly at own ship in sea-stabilized mode indicates the target is heading straight for you, yielding a CPA of zero.
Question 6: What is the primary advantage of AIS integration with ARPA in a modern radar system?
- AIS provides vessel identity and voyage data to correlate with tracked radar targets (Correct answer)
- AIS replaces ARPA tracking when radar range is reduced
- AIS improves radar antenna rotation speed
- AIS eliminates sea clutter from the radar display
Correct answer: AIS provides vessel identity and voyage data to correlate with tracked radar targets
Fusing AIS data with ARPA tracks allows the operator to associate a target's name, MMSI, and voyage info with the radar return.
CMRT CMRT Target Tracking & ARPA 2
What initial data does ARPA require from its own-ship sensors to compute accurate target tracks?