The U.S. Coast Guard is the United States government agency responsible for providing navigation services to civil and military users in the marine environment. (The environment consists of phases of navigation identified as high seas navigation, coastal and confluence navigation, and harbor and harbor entrance navigation.) This Coast Guard responsibility stems from federal law (14 USC 81), and covers aids to navigation including fixed and floating visual marks (which may carry radar reflectors or radar beacons, sound warning signals) and radio aids to navigation which include marine radiobeacons, Loran‐A, Loran‐C, and OMEGA. The paper provides an update of these radionavigation systems, and takes note of the developing Navigation Satellite Timing and Ranging, Global Positioning System (NAVSTARGPS).