What is the term for an imaginary line running in a North-South direction that intersects with the base line?

The term for an imaginary line running in a North-South direction that intersects with the base line is known as a meridian line. Meridians are crucial in the field of surveying and geographical mapping, as they help establish a reference frame for determining locations on the Earth's surface.

In a survey system, the base line serves as a parallel line that runs East-West and provides a foundational reference point for establishing meridian lines, which extend vertically from that base line. This relationship is vital in the rectangular survey system used in land descriptions, often referred to in terms of township and range.

Other terms mentioned, such as the prime meridian, refer specifically to the meridian at 0 degrees longitude, which is significant in global geography but does not generally describe the concept of meridians in relation to a base line. The equator line represents the 0-degree latitude line, running East-West, and is not relevant to North-South orientation. Thus, the recognition of a meridian line as the correct term stems from its specific role and definition within the context of directional surveying.