One important point to clear up is that corner and monument are not synonymous. A corner is a point on the earth's surface determined by the surveying process. Its location is marked by a monument which is the object or physical structure that marks a corner point. For that reason an existent corner does not necessarily mean that the monument is still there. An existent corner is one whose position can be identified by verifying the evidence of the monument, or its accessories by reference to the description in the field notes, or by an acceptable supplemental survey record, some physical evidence or valid witness testimony.

An obliterated corner is a point which has no remaining traces of the monument, or its accessories, but whose location has been perpetuated or can be recovered beyond reasonable doubt by the acts and testimony of interested land owners, competent surveyors, other qualified local authority or witnesses, or by some acceptable record evidence. But if a corner monument can be destroyed or covered over, and still there is an existent or obliterated corner point, what then is a lost corner?

A lost corner is a point of a survey whose position cannot be determined, beyond reasonable doubt, either from traces of the original marks or from acceptable evidence or testimony that bears upon the original position, and whose location can only be determined by reference to one or more interdependent corners. Such an interdependent corner is also called a control corner or controlling corner. It has been identified as an original interdependent corner and thus, can be used to control the proportionate position of a lost corner.

The definitions of existent, obliterated and lost corners can be found in the manual at 5-5, 5-9, and 5-20, respectively. As an aide, the Glossaries of Surveying and Mapping Terms is included with this course and can be accessed at anytime by selecting the Glossary button on the navigation bar.

At this point in the course, you will have an opportunity to recall and apply what you have learned.

Next, get ready for a review exercise!