What is the term for the vertical line used as a reference for land surveys?

The term for the vertical line used as a reference for land surveys is indeed the principal meridian. In land surveying, principal meridians are the primary reference lines that run north-south and are used in conjunction with baselines, which run east-west. This grid system is critical for establishing a framework for land descriptions and is particularly essential in the rectangular survey system, also known as the Public Land Survey System (PLSS).

Understanding how principal meridians function assists in accurately defining land boundaries and provides a standardized method for mapping and identifying properties. This is vital for both legal descriptions and property transactions. The other terms listed refer to different concepts. For instance, subdivision plat pertains to the layout of a specific development, power of attorney is a legal document allowing one person to act on behalf of another, and primary mortgage market refers to the arena where loans are originated. Each of these terms plays a significant role in real estate, but they do not relate to the reference lines used in land surveying.