Which reference systems affect the information displayed on the ECDIS?

• A. All of the above
• B. GPS
• C. AIS
• D. Radar overlay

Answer: (A)

ECDIS combines data from several reference sources to build what you see on the screen. The own-ship position and movements come from GPS, so the vessel’s location on the chart is tied to GNSS data. AIS provides information about other vessels—their identifiers, positions, courses, and speeds—and this data can be shown as targets on the chart. Radar overlay lets you superimpose radar returns onto the electronic chart, which requires precise alignment with the chart’s reference frame so echoes appear in the correct places relative to charted features. Since each of these systems can alter what is displayed, all of them influence the information shown on the ECDIS.