Northrop Grumman Sperry Marine VisionMaster FT, User Manual

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Navigation Tools Radar/Chart Radar User Guide
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Clearing Lines
Clearing lines are bearing lines or range
lines used to approximate a position where
a danger to own ship lies.
The clearing line bearing or range value is
used to navigate around the dangerous
area such that the mariner would want
ownship to remain no less than or no
greater than the range or bearing of the
clearing lines.
The Clearing Lines sub menu includes the following tab folders:

Editor

Monitor

I/O
The Editor tab enables you to create, save, open, edit and delete one or
more sets of clearing lines.
The Monitor tab enables you to select a previously saved set of clearing
lines for monitoring against own ship's course.
The I/O tab enables you to import or export sets of clearing lines to and
from an external device such as a USB memory stick.
Editing Clearing Lines
There are two types of Clearing Line available:

Bearing Line

Range Line
Bearing lines are drawn as a single solid line with an arrowhead towards
the line's bearing. Range lines are drawn as a single arc with arrowheads
on both the start point and end point of the arc line.
The clearing line bearing or range value is shown in the same colour
beneath the line. The clearing line may also include a label defined by the
operator.
A clearing line may be selected as a Not More Than (NMT) or Not Less
Than (NLT) value. For example, in the figure below the mariner would want
to keep the ship's bearing no less than 294.2º and no more than 315.2º to
stay in safe water.