ARPA RADAR
ARPA (Automatic Radar Plotting Aid) Radar is an advanced marine radar system that automatically tracks multiple targets and calculates their course, speed, Closest Point of Approach (CPA), and Time to CPA (TCPA). As required by SOLAS Chapter V, Regulation 19 and IMO performance standards, ARPA radar enhances collision avoidance and navigational safety.
Is ARPA radar mandatory under SOLAS?
Yes. SOLAS Chapter V, Regulation 19 requires:
Ships ≥300 GT to carry an ARPA radar or
An ATA (Automatic Tracking Aid) for smaller vessels
What is the main purpose of ARPA radar?
ARPA assists in collision avoidance by continuously tracking targets and providing CPA and TCPA data
How many targets can ARPA track?
IMO performance standards require ARPA to automatically track at least 20 targets.
What are signs that a radar antenna needs replacement?
Common indicators include:
Reduced detection range
Intermittent target loss
Abnormal noise or vibration
Increased magnetron or transmitter alarms
What information does ARPA provide?
ARPA provides:
Target course and speed
CPA & TCPA
Relative and true motion data
Collision warnings and alarms
What inputs are required for accurate ARPA operation?
ARPA requires inputs from:
Gyro compass (heading)
Speed log
Position source (GPS)
How is ARPA checked during PSC inspections?
Surveyors verify:
Target acquisition and tracking
Alarm functionality
Accuracy of CPA/TCPA
Correct sensor inputs
Why are two radar bands required on large vessels?
Using both bands improves detection reliability in varying weather conditions and provides redundancy for safety.
What happens if ARPA function fails?
The failure must be recorded, and manual plotting or alternative navigation methods must be used until repairs are completed.
What is the difference between X-Band and S-Band radar?
X-Band (9 GHz): High resolution, excellent for short range, small targets, and navigation in coastal waters.
S-Band (3 GHz): Better performance in rain, fog, and heavy seas, ideal for long-range detection and open-sea navigation.
Conclusion
ARPA radar is a critical SOLAS-mandated collision avoidance system that enhances situational awareness and navigational safety. When correctly installed, properly integrated, and operated by trained personnel in accordance with IMO guidelines, ARPA significantly reduces the risk of collision at sea.