 The use of radial lines on a map for measurement, planning, and regulation of radio transmissions is called the "radial method".It has no relation to grounding radials described above.In the field of transmission planning, radials are evenly spaced points (vectors) along evenly spaced lines (bearings) from a common point on a map, which are used to determine the average elevation above mean sea level (AMSL) within a radio station's broadcast range (including broadcast stations and cellphone base stations, among others).