What is the function of EBL and VRM in ARPA?

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Multiple Choice

What is the function of EBL and VRM in ARPA?

In ARPA, you measure a target’s position in polar coordinates—angle and distance—using specialized markers on the radar display. An Electronic Bearing Line is a rotatable line that emanates from your own-ship symbol; you align it so it passes through the target. The angle of that line relative to your heading gives the relative bearing to the target, which is how far off to one side the target is. A Variable Range Marker is a marker you set along the radar’s range scale from your ship outward. You move it until it sits at the target’s position, and the distance from your ship to the target is read directly from the range scale. In practice, you use the EBL to lock in the bearing and the VRM to lock in the range, which together let you plot the target’s position and track its relative motion. These tools are fundamental for ARPA plotting and collision avoidance, as they provide the basic bearings and distances needed for predicting target courses and speeds. The other options describe functions not related to EBL or VRM—wind measurements, target size or vessel type displays, or unrelated features—so they don’t fit what EBL and VRM do.

In ARPA, you measure a target’s position in polar coordinates—angle and distance—using specialized markers on the radar display. An Electronic Bearing Line is a rotatable line that emanates from your own-ship symbol; you align it so it passes through the target. The angle of that line relative to your heading gives the relative bearing to the target, which is how far off to one side the target is.

A Variable Range Marker is a marker you set along the radar’s range scale from your ship outward. You move it until it sits at the target’s position, and the distance from your ship to the target is read directly from the range scale. In practice, you use the EBL to lock in the bearing and the VRM to lock in the range, which together let you plot the target’s position and track its relative motion.

These tools are fundamental for ARPA plotting and collision avoidance, as they provide the basic bearings and distances needed for predicting target courses and speeds. The other options describe functions not related to EBL or VRM—wind measurements, target size or vessel type displays, or unrelated features—so they don’t fit what EBL and VRM do.

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