Which of the following may be used to satisfy the EPFS requirement of an ECDIS?

• A. GNSS
• B. All of the Above
• C. DGPS
• D. Radar overlay

Answer: (B)

Electronic Position Fixing System (EPFS) means the source that provides the vessel’s position to the ECDIS so the chart can be correctly georeferenced. GNSS gives a direct position fix with precise timing, which is a standard EPFS source. DGPS enhances GNSS by correcting errors in real time, improving accuracy and integrity, so it also satisfies EPFS requirements. Radar overlay isn’t a position source by itself, but in an integrated ECDIS setup it is anchored to the chart using the position data from GNSS or DGPS; when the system is configured to accept radar overlay as part of the navigational fix, it contributes to the EPFS solution. Because an ECDIS can accept any of these as part of its position reference, all of the above are valid ways to satisfy the EPFS requirement.