Real Estate Salesperson · Real property characteristics, legal descriptions and property use · 6 min read
Rectangular Survey System and Lot and Block
- Understand the structure, reference lines, and subdivisions of the rectangular survey system, including townships and sections.
- Calculate acreage accurately for standard aliquot parts, combined parcels, and understand the role of fractional sections and government lots.
- Explain the components, creation, and recording process of the lot-and-block legal description system.
The Framework of the Rectangular Survey System
Real estate salespersons must understand how land is legally identified and described. While sales agents work under the guidance of a supervising broker, every licensee is expected to review and interpret legal descriptions with care. One of the primary methods used in the United States is the rectangular survey system, which is also known as the government survey system or the Public Land Survey System (PLSS). This system was originally established by the federal government to survey and describe public domain lands using a standardized grid.
The rectangular survey system is built on intersecting reference lines known as principal meridians and base lines. Principal meridians are imaginary survey lines that run true north and south, and each principal meridian has a unique identifying name. Base lines are imaginary survey lines that run true east and west. Each principal meridian is intersected by an assigned base line, and the specific geographic point where a principal meridian intersects its base line is called the initial point.
From this initial point, additional lines are surveyed at regular intervals to establish a uniform grid. Range lines run generally north and south at nominal six-mile intervals from a principal meridian; lines following true north converge rather than remain parallel. These range lines create north-south strips of land that are six miles wide, known as ranges. Ranges are numbered consecutively east or west of the designated principal meridian. Similarly, lines running parallel to the base line at six-mile intervals are called township lines. Township lines create east-west strips of land that are six miles wide, known as township tiers. Township tiers are numbered consecutively north or south of the designated base line.
Where township lines and range lines intersect, they form nominally square tracts of land called townships. A standard township measures 6 miles by 6 miles, covering an area of 36 square miles and possessing a perimeter of 24 miles. When writing or reading a legal description of a township, the description includes its tier designation, its range designation, and the name of its principal meridian.
| Line Type | Direction Run | Spacing Interval | Area Formed |
|---|---|---|---|
| Principal Meridian | True North and South | Designated reference line | Reference axis for ranges |
| Base Line | True East and West | Designated reference line | Reference axis for township tiers |
| Range Lines | True North and South | 6-mile intervals from meridian | Ranges (6-mile-wide north-south strips) |
| Township Lines | True East and West | 6-mile intervals from base line | Township tiers (6-mile-wide east-west strips) |
Common mistakes
- Dividing continuously through the word 'and' in acreage math problems instead of calculating each tract separately and adding the totals together.
- Assuming Section 36 is in the southwest corner of a township rather than the southeast corner, or forgetting that section numbering zigzags back and forth.
- Believing all sections contain exactly 640 acres, overlooking that fractional sections and government lots occur along northern and western township boundaries or along water bodies.
- Confusing range lines with township lines, or forgetting that ranges run north-south while township tiers run east-west.
Key points
- The rectangular survey system (PLSS) surveys public domain land using north-south principal meridians and east-west base lines intersecting at an initial point.
- Township lines run east-west at 6-mile intervals to form tiers, while range lines run north-south at 6-mile intervals to form ranges.
- A standard township is nominally 6 miles by 6 miles and is divided into 36 sections; actual township dimensions and section acreages can vary, including in fractional sections.
- Sections are numbered 1 to 36 in a snake-like pattern starting in the northeast corner and finishing with Section 36 in the southeast corner; Section 16 was historically reserved for school support.
- Curvature corrections occur every 24 miles via correction lines and guide meridians forming government checks, concentrating irregular acreage into fractional sections (1-6, 7, 18, 19, 30, 31) and government lots.
- For standard nested aliquot parts of a section, multiply the fractional denominators and divide 640 by the product; calculate parts joined by 'and' separately and add only nonoverlapping acreage.
- The lot-and-block (recorded plat) system originates from larger surveyed tracts, identifies lots and blocks on an approved and recorded county plat, and may include dedication of streets or parks.
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