Navigation & Chart Integration Flashcards

What is the VRM (Variable Range Marker) used for in radar navigation?

Answer: Measuring the range to a specific target or point of interest on the radar display

The VRM is an adjustable range ring that can be set to coincide with any target, allowing the navigator to read off an accurate distance to that target.

What does the EBL (Electronic Bearing Line) measure on a radar display?

Answer: The bearing from own ship to a specific target or landmark

The EBL is a rotatable line originating from own ship's position that allows the navigator to measure the bearing to any point on the radar display.

What does 'north-up' orientation mean on a radar display?

Answer: True north is always at the top of the display regardless of ship's heading

In north-up orientation, the radar picture is stabilized so that true north is always at the top of the display, making it easier to correlate with a north-up chart.

Under COLREGS Rule 7, what obligation does a vessel have regarding the use of radar?

Answer: Radar, if fitted and operational, must be used to obtain early warning of risk of collision

COLREGS Rule 7 states that every vessel shall use all available means including radar to determine if risk of collision exists.

What is the significance of the 'trial maneuver' function in ARPA systems?

Answer: It simulates the effect of a proposed course or speed change on CPA and TCPA before executing the maneuver

The trial maneuver function allows the watchkeeper to input a proposed course or speed change and see how it would affect predicted CPAs before actually maneuvering.

What is a radar blind sector, and how is it typically marked on a display?

Answer: An angular sector where the radar signal is blocked by a vessel's own superstructure; marked with sector lines or a warning note

A blind sector is an angular zone where the radar beam is obstructed by the ship's mast, funnel, or other superstructure, creating an area with no or degraded target detection.