Longitude

Longitude is the east–west coordinate of a vessel’s position, expressed in degrees east or west of the Prime Meridian at Greenwich. Lines of longitude run from pole to pole and, when paired with latitude, give a precise position for plotting on nautical charts, electronic chartplotters, and navigation systems.

For boaters, accurate longitude is essential for fixing position, checking distance off hazards, entering waypoints, and confirming progress on passage. It works with Latitude, GPS, and a Chartplotter to keep routes aligned with safe water, traffic separation, tide gates, and weather windows. A small longitude error can put a vessel miles from its intended track, especially offshore.

In PredictWind, longitude is used whenever you set a start point, destination, waypoint, forecast location, or tracking position. Weather Routing combines your coordinates with wind, wave, current, and tidal data to calculate safe, efficient routes, while the Offshore App and DataHub can use GPS-derived longitude for position reports and forecast downloads at sea.