Raytheon Pathfinder ECDIS Operator's Manual page 278

ECDIS calculates the current cross−track error as the perpendicular
distance between your ship's position and the intended track.
The cross−track deviation limit establishes the width of the fairlanes and of the
vessel's searchlight. If the cross−track error is set to 0.5 NM, fairlane and
searchlight width would be equal to 1NM. Please see "The Ship's Heading
Vector and Anti Grounding Look Ahead", chapter 7.1.6.
When the alarm is triggered, ECDIS displays the message "Warning Cross−track
Error greater than value specified".
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Operator Manual
Cross Track Deviation Limit violation
ECDIS generates an alarm to indicate violation of cross−track limits
(the Cross Track Deviation Limit is defined in the Alarms dialog box
shown in Figure: 1−38 and can also be set in the Create/Change
Route dialog (see chapter 8.2.1.2 (7)).
Figure: 1−38 Cross−track Error
8−50
NOTE
Edition: 30.MAR.2007