Introduction ECDIS is a real-time navigation system that integrates a variety of chart and navigation-related information. More than simply a replacement for a paper nautical chart, ECDIS is capable of continuously determining a vessel’s position in relation to land, charted objects, aids-to-navigation, and unseen hazards. Increasingly, ECDIS is being used for both navigation and collision avoidance tasks. In this regard, there is growing concern about the display of ever-increasing amounts of chart and navigation-related information. When it comes to using ECDIS, more information is not necessarily better. Too much information can clutter the display and confuse the user. In this regard, there is a need to “harmonise” the simultaneous display of both chart and navigation-related information.