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Land Surveying Units

All measurements for Land surveying must be referenced to the Standard United States or metric measurements.

Distance and Elevation must comply with the U.S. Survey Foot and/or metric units and sub units of the same.  Angles must be referenced in degrees, decimal degrees, radians, azimuths, or bearings.  If any other standards of measurement are used it must be referenced and a conversion factor must be noted as well (ex.  chains, rods, poles, perches).

Land Survey Unit

Common Land Survey Measurement Units

Acre - The English acre is a unit of area equal to 43,560 square feet, 10 square chains, or 160 square poles. It originates from a plowing area that is 4 poles wide and a furlong (40 poles) long. A square mile is 640 acres. A Scottish acre is 1.27 English acres. An Irish acre is 1.6 English acres.

Arpent - Unit of length and area used in Louisiana, Canada and France.  As a unit of length, an arpent is approximately 191.8 feet. The (square) arpent is a unit of area, approximately 0.845 acres, or 36,802 square feet.

Chain - Unit of length usually understood to be Gunter’s chain, see also Rathborn chain. The name comes from the heavy metal chain of 100 links that surveyors used to measure property bounds.

Compass - One toise.

Engineer's Chain - A 100 foot chain containing 100 links of one foot a piece.

Furlong - Unit of length equal to 40 poles (220 yards). The name originates from "furrow long", the length of a furrow that oxen can plow before they are rested and turned. See Gunter's chain.

Ground - A unit of area equal to 2400 sq. ft., or 220 sq. meters.  This unit of measurement is often used in India.

Gunter's Chain - Unit of length equal to 66 feet, or 4 poles. Developed by English polymath Edmund Gunter in the early 1600's, the standard measuring chain revolutionized surveying. Gunter's chain was 22 yards long, one tenth of a furlong.  This was a common unit of length used in the old days.  An area one chain wide by ten chains long was exactly an acre. In 1595 Queen Elizabeth I redefined the mile from the old Roman value of 5000 feet to 5280 feet in order for it to be an even number of furlongs. A mile is 80 chains.

Hectare - Metric unit of area equal to 10,000 square meters, or 2.471 acres, or 107,639 square feet.

Hide - A very old English unit of area, a hide was of variable size depending on the quality of the land. It was the amount of land to support a family, and ranged from 60 to 180 acres. After the Norman conquest in 1066 it became standardized at around 120 acres.

Hundred - An adminstrative area larger than a village and smaller than a county. In England it was 100 hides in size, and the term was used for early settlements in Virginia, Maryland, and Delaware.

Labor - The labor is a unit of area used in Mexico and Texas. In Texas it equals 177.14 acres (or 1 million square varas).

League (legua) - Unit of area used in the southwest U.S., equal to 25 labors, or 4428 acres (Texas), or 4439 acres (California).  League’s can be used as a unit of length as well, one league is equal to approximately three miles.

Link - Unit of length equal to 1/100 chain (7.92 inches).

Morgen - Unit of area equal to about 0.6309 acres. It was used in Germany, Holland and South Africa, and was derived from the German word Morgen ("morning").  It represented the amount of land that could be plowed in a morning.

Out - an 'out' is a single extension of a chain in the field.  Therefore, if you measured a course 20 chains long with a 2 pole chain there would be 40 'outs'.  Ten chain lengths is a tally.  The surveyor usually carried 'tally pins', tallies, to count the number of chain lengths in a given line. Tally pins looked like a 14 inch bar-b-que skewer and sometimes with a lead weight near the pointed end and a bit of red cloth tied to the ring at the top end.

Perch - See pole.

Point - A point of the compass. There are four cardinal points (North, South, East, West), and 28 others yielding 32 points of 11.25 degrees each. A survey line's direction could be described as a compass point, as in "NNE" (north northeast).  To improve precision, the points would be further subdivided into halves or quarters as necessary, for example, "NE by North, one quarter point North". In some areas, "and by" meant one half point, as in "NE and by North".

Pole - Unit of length and area.  Also known as a perch or rod.  As a unit of length, one pole is equal to 16.5 feet.  A mile is 320 poles.  As a unit of area, one pole is equal to a square with sides one pole long. An acre is 160 square poles.  It was common to see an area referred to as "87 acres, 112 poles", meaning 87 and 112/160 acres.

Pueblo - A Spanish grant of less than 1000 acres.

Rancho - A Spanish grant of more than 1000 acres.

Rathbone's Chain - A measuring chain two poles, or 33 feet, in length.

Rod - See pole.

Rood - Unit of area usually equal to 1/4 acre.

Toise - Traditional French unit of length equal to 6 old French 'pieds' or feet, or 6.4 English feet.

Vara - Unit of length (the "Spanish yard") used in the U.S. southwest.  The vara is used throughout the Spanish speaking world and has values around 33 inches, depending on locale.  The legal value in Texas was set to 33 1/3 inches early in the 1900's.

Virgate - An old English unit of area, equal to one quarter of a hide.  The amount of land needed to support a person.

Land Survey Units

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