On discussion of equivalent earth's radius

There are two different definitions of equivalent earth's radius, and the rationality of the two definitions and application scope are controversial. In this paper, the two different definitions of the equivalent earth's radius were introduced, the signification of the equivalent earth's radius was construed in detail, the mapping relationship of the ray parameters of the equivalent earth and the true earth is given, the differentia and relationship between the two definitions are discussed thoroughly, as well as the applications limitations.