What is the Difference between lost and obliterated corners?

Answer 1

According to the 1974 edition of "Restoration Of Lost Or Obliterated Corners & Subdivision Of Sections a guide for surveyors:

A lost corner is a point of a survey whose position cannot be determined, beyond a reasonable doubt, either from traces of the original marks of from acceptable evidence of testimony that bears upon the original position, and whose location can be restored only by reference to one or more interdependent corners.

An obliterated corner is one at whose point there are no remaining traces of the monument, or it's accessories, but whose location has been perpetuated, or the point for which may be recovered by the acts of testimony of the interested land owners, competent surveyors, or other qualified local authorities, or witnesses, or by some acceptable record evidence.