Base Line
An east-west reference line running through an initial point, from which townships are numbered north and south.
Detailed Definition
A base line is a surveyed line running east and west (parallel to the equator) through an initial point, serving as the primary reference for measuring townships in the Public Land Survey System (PLSS).
Characteristics: - Runs due east and west (parallel of latitude) - Passes through the initial point - Serves as the zero line for township numbering - Intersects the principal meridian at the initial point
Function in PLSS: - Townships are numbered north and south from the base line - Example: T3N means Township 3 North of the base line - Combined with range numbers to locate land - Forms the horizontal axis of the survey grid
Survey procedure: - Surveyed as a true parallel of latitude - Standard parallels (correction lines) run parallel at 24-mile intervals - Compensates for convergence of meridians toward poles
Relationship to other lines: - Township lines run parallel to the base line - Range lines run perpendicular to the base line - Together they create the township grid
Base lines and principal meridians form the foundational framework for all PLSS land descriptions.
Related Terms
PLSS
The Public Land Survey System, a method of subdividing and describing land in the United States using townships, ranges, and sections.
Township, Range, and Section
The hierarchical land description system within PLSS, identifying land by its position relative to principal meridians and base lines.
Initial Point
The geographic starting point from which all PLSS surveys in a given region originate, established by astronomical observation.
Principal Meridian
A north-south reference line running through an initial point, from which ranges are numbered east and west.