The Loran-C Radionavigation System, managed by the U.S. Coast Guard, is the federally provided radionavigation system for civil marine use in the U.S. coastal waters. It is also designated by the Federal Aviation Administration (FAA) as a supplementary system in the National Airspace System (NAS). This system provides accurate radionavigation and timing services to users in the United States of America and Canada. Loran-C is also being used and developed by several other countries in Europe and Asia. Estimates of Loran-C system accuracy must take into consideration the transmitted signal, signal propagation, signal reception, interference or errors from outside sources such as natural and man-made electromagnetic noise, skywave contamination, geometric dilution of precision, other Loran-C signals, communication information superimposed on the navigation signal, and coordinate conversion.