CMRT CMRT Navigation Integration & Display Systems

Question 1

What is the primary purpose of ARPA (Automatic Radar Plotting Aid) in marine radar systems?

Accepted Answer

To automatically track targets and predict collision risk

Answer

ARPA automatically tracks radar targets, calculating their course, speed, and closest point of approach (CPA) to assess collision risk.

Question 2

In a radar overlay on an Electronic Chart Display (ECDIS), what must be synchronized between the two systems?

Accepted Answer

Position reference and heading data

Answer

Accurate radar overlay on ECDIS requires synchronized position (GPS) and heading data so radar returns align correctly with the chart.

Question 3

Which display mode shows radar targets relative to the vessel's bow and rotates as the ship turns?

Accepted Answer

Head-Up

Answer

Head-Up mode displays targets relative to the ship's bow, with the top of the screen always representing the direction the vessel is heading.

Question 4

What does 'sea clutter' on a radar display represent?

Accepted Answer

Returns caused by rough sea surface waves near the antenna

Answer

Sea clutter consists of radar returns from wave surfaces near the vessel, which can mask genuine targets at short range.

Question 5

Which NMEA sentence is most commonly used to feed GPS position data into a marine radar system?

Accepted Answer

NMEA $GPGLL or $GPRMC

Answer

$GPGLL (geographic position) and $GPRMC (recommended minimum data) both carry latitude/longitude and are standard feeds for radar position input.

(CMRT) Certified Marine Radar Technician Practice Test