What does it mean when your GPS displays that you are off course?

When your GPS indicates that you are off course, it typically refers to a cross track error. This is a measure of how far your actual position deviates from the intended or planned track. In nautical navigation, the intended route is pre-defined, and the GPS continuously checks your current position against that route. If you drift away from the designated track line, the GPS will register this deviation as a cross track error, which is crucial for navigating back to the intended course.

Understanding cross track error is essential for safe navigation. It informs the navigator that they need to adjust their heading or make corrections to align back with the planned route. This kind of information aids in maintaining situational awareness, ensuring that you remain on course and can manage any potential drift due to currents, wind, or other navigational factors.

In contrast, positioning error usually pertains to inaccuracies in the GPS signal itself, navigational drift describes shifts away from a position over time due to environmental factors, and routing failure indicates issues with the planned path rather than the real-time position concerning that path.