What is calculated as the distance between the planned route and the actual vessel position in ECDIS?

The distance between the planned route and the actual vessel position in an Electronic Chart Display and Information System (ECDIS) is referred to as Cross-Track Error. This term is crucial in navigation as it provides navigators with immediate information about how far their vessel deviates from the intended course.

Understanding Cross-Track Error enables mariners to make necessary course corrections to ensure safety and efficiency. It quantifies lateral displacement from the ideal track, which is significant for maintaining accurate navigation, especially in areas with critical navigational hazards or specific traffic patterns.

In contrast, terms like offset distance and navigation error might seem related but do not specifically describe the deviation from the planned route in the same way. Drift refers to the unintended movement of a vessel due to external forces like currents or wind, not the positional discrepancy from a planned route. Thus, Cross-Track Error directly and accurately characterizes the deviation from the intended route, making it the correct choice in this context.