The survey grid

Sections of township

Fractions of a section

Converting section fractions to acres

To institute the system, all affected land was surveyed using latitude (east-west) and longitude (north-south) lines. The object was to create uniform grids of squares, called townships, which would have equal size and be given a numerical reference for identification.

The rectangular survey system works well for describing properties that are square or rectangular in shape, since these can be described as fractions of sections. However, for an irregular shape, such as a triangle, the rectangular system is inadequate as a method of legal description. The full description has to include a metes and bounds or lot and block description.

The survey grid         

The following exhibit shows a portion of the rectangular survey system.

Meridian. The north-south, longitudinal lines on the survey grid are meridians. The principal meridian is the single designated meridian for identifying townships in the principal meridian’s geographical “jurisdiction.” There are 37 principal meridians in the national survey. In the exhibit, the principal meridian is the Tallahassee Principal Meridian.

Parallel. The east-west, latitudinal lines are called parallels. The base parallel or base line is the designated line for identifying townships. There is a base parallel for each principal meridian

Correction lines. Because the earth is curved, meridians (including all range lines and north-south section lines) converge toward one common point at the north pole. Using meridians without correction would result in the north end of every township (and section) being narrower than its south end. To maintain a rectangular survey pattern on the earth’s curvature, adjustments need to be made every 24 miles by a longitudinal shift of the standard parallels. The adjusted lines, called correction lines or standard parallel lines, restore the meridians to their original spacing, resulting in a slight eastward or westward shift between each row of quadrangles or every fourth township line.

Range. The north-south area between consecutive meridians is called a range. The area labeled “B” in the exhibit is a range. A range is identified by its relationship to the principal meridian. All ranges are six miles wide.

The principal meridian divides all ranges into east ranges and west ranges.  A range to the west of the principal meridian is identified by an “R” for range, a number representing its ordinal position from the principal meridian, and a “W” representing that it is west of the principal meridian.  For example, the third range west of the principal meridian would be denoted “R3W.”  A range east of the principal meridian is designated “E” instead of “W.”  Thus the fifth range east of the principal meridian would be identified as “R5E.”

Tier. The east-west area between two parallels is called a tier, or a township strip. The area marked “C” in the exhibit is a tier. A tier is identified by its relationship to the base parallel. All tiers are six miles wide.

The principal base line in a survey area divides tiers into north tiers and south tiers.  A tier is identified by a “T” for tier, a number representing its ordinal position from the base line, and an “N” or “S” for north or south, respectively, of the base line.  Thus the eighth tier to the north of the base line would be identified as “T8N.”

Township. A township is the area enclosed by the intersection of two consecutive meridians and two consecutive parallels, as the shaded square marked “A” in the exhibit illustrates. Since the parallels and meridians are six miles apart, a township is a square with six miles on each side. Its area is therefore 36 square miles.

Individual townships are identified by their tier and range identification taken together, with the tier designation named first.  For example, a township two tiers south of the base line and three ranges east of the principal meridian would be denoted as “T2S, R3E.”

Sections of a township                  

The rectangular survey system divides a township into thirty-six squares called sections. Each side of a section is one mile in length. Thus the area of a section is one square mile, or 640 acres. As the next exhibit illustrates, the sections in a township are numbered sequentially starting with Section 1 in the northeast corner, proceeding east to west across the top row, continuing from west to east across the next lower row, and so on, alternately, ending with Section 36 in the southeast corner.

Fractions of a section                   

A section of a township can be divided into fractions as the next exhibit shows.

Describing a section fraction. A fraction of a section is legally described by indicating its size and location within successively larger quarters or halves of the section.  In other words, the description proceeds from the smallest unit to the largest.

In the exhibit, the area marked “A” is one quarter of Section 8, located in the section’s southeast corner.  Its legal description first indicates its location (SE) in the next larger unit, in this case, the section.   Second, the description states the fractional portion (1/4) of the next larger unit.  Third, the description identifies the next larger unit, Section 8, and ends.  Thus, the description is:

The SE 1/4 of Section 8

The area marked “B” consists of the western half of the northwest quarter of the section.  Its legal description is:

The W 1/2 of the NW 1/4 of Section 8

Area C consists of the eastern half of the northeast quarter of the northeast quarter of the section.  Its legal description is:

The E 1/2 of the NE 1/4 of the NE 1/4 of Section 8

In sum, the method of describing a fraction of a section is:

  • Proceed from the smallest unit to the largest, ending with the section.
  • First name the location of the unit within the next larger unit, then its fraction of the next larger unit.
  • Repeat step (2) until you reach the section itself.  Give the section number.

 Converting section fractions to acres. The size in acres of a subsection of a township is a fraction of 640 acres, since there are 640 acres in a section.

For example, the SW 1/4 of a section is one quarter section. Thus, its acreage is one quarter of 640, or 160 acres. Going further, the E 1/2 of the SW 1/4 is one half of that one quarter, or 80 acres. The E 1/2of the SW 1/4of the SW ¼ is 20 acres.

A quick method of calculating the acreage of a parcel from its legal description is as follows:

  • Multiply the denominators of the fractional descriptions together.
  • Divide 640 by the resulting number.

Applying this method to the foregoing descriptions, we get: