ABSTRACT
The current Federal Communications Commission (FCC) Rules for distance calculations use two methods: "flat-earth" and "spherical-earth." The spherical-earth method uses conventional spherical trigonometry to determine the distance. In August 1987, the Canadian government adopted the truncated and fudged arc-length formulas, which had been implemented by the FCC in Docket 80–90. The August 11, 1992, US-Mexican frequency modulated (FM) Agreement specifies the spherical-earth method exclusively; there is no provision for using the FCC flat-earth method for short to moderate distances. The Mexican Agreement further specifies that azimuths are to be calculated on a spherical-earth basis. There continues to be an inconsistency in rounding practices between the FCC FM and TV Rules. With the widespread availability of low-cost Global Positioning System (GPS) receivers and the termination of "selective availability," a technique formerly used to deny the full accuracy of GPS to parties not friendly to the United States, a typical consumer-grade GPS receive.
