US satellite-based radionavigation system providing position, velocity, and time data worldwide to marine and other users.
Quick facts
Regulation
SOLAS Chapter V
In practice
The OOW must understand the accuracy limitations of GPS: position error increases near steep terrain that can mask satellite signals, in polar regions with poor satellite geometry, and in areas where adversaries deploy jammers or spoofers. The Admiralty Manual of Navigation recommends cross-checking GPS positions against independent methods—visual fixes, radar ranges, and depth soundings—whenever proceeding in coastal or restricted waters. Flag states increasingly require bridge teams to demonstrate proficiency in recovering position by traditional means should GPS become unreliable, a competency examined under STCW Table A-II/1.
Regulatory detail & full definition
The Global Positioning System (GPS) is a US Department of Defense satellite constellation providing continuous, worldwide position, velocity, and time data to an unlimited number of receivers. At sea, GPS has become the primary source of vessel position for chart plotting, ECDIS, autopilot steering, AIS transponder input, VDR, and LRIT. Under SOLAS Chapter V and IMO Resolution A.953(23) on the world-wide radionavigation system, GPS is recognised as one of the core components of the integrated navigation system, though no single navaid is to be relied on exclusively.
The OOW must understand the accuracy limitations of GPS: position error increases near steep terrain that can mask satellite signals, in polar regions with poor satellite geometry, and in areas where adversaries deploy jammers or spoofers. The Admiralty Manual of Navigation recommends cross-checking GPS positions against independent methods—visual fixes, radar ranges, and depth soundings—whenever proceeding in coastal or restricted waters. Flag states increasingly require bridge teams to demonstrate proficiency in recovering position by traditional means should GPS become unreliable, a competency examined under STCW Table A-II/1.