Explanation: The Global Positioning System (GPS) is a worldwide satellite-based navigation system that provides precise, continuous position, velocity, and time information. GMDSS (Global Maritime Distress and Safety System) equipment, such as DSC radios, Inmarsat terminals, and some EPIRBs, relies on an accurate and constantly updated vessel position to effectively transmit distress alerts and facilitate search and rescue operations. A GPS receiver integrated into or interfaced with GMDSS equipment supplies this crucial positioning data. COSPAS-SARSAT is an international satellite system for detecting and locating distress beacons, not a source of continuous navigation for a vessel. An EPIRB is a distress beacon that transmits position data in an emergency, it doesn't *provide* continuous position *to* other GMDSS equipment. Inmarsat-B is a communication service, not a positioning system itself.