# effective Earth radius

**effective Earth radius:** The radius of a hypothetical Earth for which the distance to the radio horizon, assuming rectilinear propagation, is the same as that for the actual Earth with an assumed uniform vertical gradient of atmospheric refractive index. (188) *Note:* For the standard atmosphere, the effective Earth radius is 4/3 that of the actual Earth radius.

This HTML version of FS-1037C was last generated on Fri Aug 23 00:22:38 MDT 1996