Cross Track Error Calculator
Enter a planned track from waypoint A to waypoint B and your vessel position P. The calculator returns the cross track error (the perpendicular distance from your position to the track), the side of the track you are on (port or starboard), and your progress along the leg.
Track start (A)
Tip: paste a full pair here, for example 51.5074, -0.1278 or 51° 30′ N, 0° 07′ W
Track end (B)
Tip: paste a full pair here, for example 51.5074, -0.1278 or 51° 30′ N, 0° 07′ W
Vessel position (P)
Tip: paste a full pair here, for example 51.5074, -0.1278 or 51° 30′ N, 0° 07′ W
Calculate cross track error (XTE)
Cross track error (XTE) is the perpendicular distance from your position to the planned track — the great-circle line between two waypoints. It is computed with the standard spherical cross-track formula, the same method GPS receivers and chartplotters use.
The calculator also reports:
- Side of track — whether your position lies to port (left) or starboard (right) of the track, facing from A towards B.
- Along track from A — how far along the leg the point abeam of your position lies.
- Along track to B — the along-track distance remaining to the end waypoint.
Reading the result
A chartplotter shows XTE as a steering bar: the further off track, the more correction is needed. Steer towards the track to bring the error back to zero — if you are to starboard of the track, steer to port, and vice versa.
Notes
- The track is a great circle, not a rhumb line — over short coastal legs the difference is negligible.
- Works together with the Distance Calculator and Bearing Calculator, which share the same Point A / Point B inputs.
- For passage planning and study only — not for live navigation. The map is a road/satellite map, not a nautical chart: it shows no depths, hazards, or aids to navigation.