XTE Cross Track Error

In maritime terminology, XTE cross track error is a way for sailors and navigators to tell at a glance what their distance to port (left) or starboard (right) of their intended straight track between two waypoints is.

These waypoints may be departure, arrival or transit points that are set on a chart. Cross track error (XTE) is most commonly caused by drift due to environmental reasons and corrective action should be taken as soon as possible.