In terms of legal descriptions, what is a principal meridian?

A principal meridian is a reference point for measuring land, specifically in the context of the Public Land Survey System (PLSS) used in the United States. The principal meridian runs north and south, serving as a longitudinal baseline from which land can be surveyed and divided into townships and sections. This system is crucial for establishing precise locations and boundaries for property, allowing for organized land use and ownership documentation.

In this context, the other options do not define a principal meridian accurately. While a line defining latitude refers to lines that run east-west, a principal meridian specifically pertains to north-south orientation. Similarly, although surveyors do utilize landmarks as part of their work, the term "landmark" is not synonymous with principal meridian, which is a specific type of control line used in surveying. Lastly, a type of legal agreement does not relate to the geographical concepts of land measurement or surveying at all.