Simrad AP27 Manual page 148

Simrad AP26 and AP27 Autopilots
True bearing – Bearing relative to true north; compass bearing
corrected for compass error.
True heading – Heading relative to true north (the meridian).
Waypoint - A discrete point, stored in a navigator, located on
the surface of the earth. Normally this point will be identified by
Lat/Lon coordinates although in some systems it may be shown
by T.D.'s.
XTE - Cross Track Error - Used to identify a vessels position
relative to a straight line drawn between two waypoints. The
amount the vessel is off to the left or to the right of this line is
known as the track. It is normally displayed in thousands of a
nautical mile, equal to 6 ft or 1.85 m.
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