The Radio Navigational Aids (Publication 117) publication contains a detailed list of selected worldwide radio stations that provide services to the mariner.^[1] The publication is divided into chapters according to the nature of the service provided by the radio stations.^[1] The services include Radio direction finder and Radar Stations; stations broadcasting navigational warnings, time signals or medical advice; communication traffic for distress, emergency and safety including the Global Maritime Distress Safety System (GMDSS) and long range navigational aids.^[1] It also contains chapters describing procedures of the AMVER System, and the interim emergency procedures and communication instructions to be followed by U.S merchant vessels in times of crisis.^[1] A new edition of Publication 117 is published annually.^[1] This publication is available in its entirety on the website and there are also database queries available for much of the data contained within.^[1]