Effective Earth radius

In telecommunication, effective Earth radius is 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.

Note: For the standard atmosphere, the effective Earth radius is 4/3 that of the actual Earth radius.

References

 This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).