CMRT Navigation & Chart Integration 1 — Questions and Answers
Question 1: What does ARPA stand for in marine radar systems?
- Automatic Radar Plotting Aid (Correct answer)
- Advanced Radar Processing Array
- Automated Range and Position Adjuster
- Analog Radar Pulse Amplifier
Correct answer: Automatic Radar Plotting Aid
ARPA stands for Automatic Radar Plotting Aid, a system that automatically tracks radar targets and calculates collision risk data.
Question 2: What is the primary purpose of radar overlay on an ECDIS display?
- To add color to the chart
- To superimpose live radar returns onto the electronic chart for correlated situational awareness (Correct answer)
- To replace the paper chart backup
- To increase the radar transmission power
Correct answer: To superimpose live radar returns onto the electronic chart for correlated situational awareness
Radar overlay on ECDIS superimposes live radar returns onto the electronic navigational chart, enabling direct comparison of radar contacts with charted features.
Question 3: In radar navigation, what does 'true motion' display mode show?
- All targets moving relative to own ship
- Own ship and targets moving according to their actual courses and speeds over ground (Correct answer)
- Only stationary land targets
- Only vessels under 300 gross tons
Correct answer: Own ship and targets moving according to their actual courses and speeds over ground
True motion mode moves own ship across the display according to its actual course and speed, while stationary objects remain fixed and moving targets reflect their real movement.
Question 4: What is the purpose of a parallel index (PI) line in radar navigation?
- To measure the radar beam width
- To maintain a safe passing distance from a navigational hazard by tracking a fixed bearing line (Correct answer)
- To calibrate the radar's north alignment
- To set the pulse repetition frequency
Correct answer: To maintain a safe passing distance from a navigational hazard by tracking a fixed bearing line
A parallel index line is drawn parallel to the intended track at a set distance from a hazard, allowing the navigator to monitor safe clearance continuously.
Question 5: What is MARPA, as distinguished from full ARPA, in marine radar?
- A manual plotting system requiring paper charts
- Mini Automatic Radar Plotting Aid, a simplified target-tracking feature found on smaller vessel radars (Correct answer)
- A military-grade radar system
- A radar frequency band used in coastal waters
Correct answer: Mini Automatic Radar Plotting Aid, a simplified target-tracking feature found on smaller vessel radars
MARPA (Mini Automatic Radar Plotting Aid) provides limited automatic target tracking on smaller, less powerful radars compared to full ARPA systems.
Question 6: Which NMEA sentence is most commonly used to transfer radar target data to an ECDIS or chartplotter?
- NMEA 0183 TTM (Tracked Target Message) (Correct answer)
- NMEA 2000 PGN 127250
- NMEA 0183 GLL
- IEC 61162-1 VHW
Correct answer: NMEA 0183 TTM (Tracked Target Message)
The NMEA 0183 TTM (Tracked Target Message) sentence transmits ARPA/MARPA tracked target data including bearing, range, CPA, and TCPA to connected navigation systems.
CMRT Navigation & Chart Integration 1
What does ARPA stand for in marine radar systems?