7.92 inches are 1 link.
25 links are 1 rod.
4 rods or 100 links are 1 chain.
A rod is 16 1/2 feet.
A chain is 66 feet or four rods.
A mile is 320 rods, 80 chains or 5,280 feet.
An acre contains 43,560 square feet.
An acre contains 160 square rods.
An acre is 208.71 feet square.
Square chains x 0.10=acres.
40 chains equal 160 rods or 2,640 feet.

Units of Measure   

Acre - The (English) acre is a unit of area equal to 43,560 square feet, or 10 square chains, or 160 square poles. A square mile is 640 acres. The Scottish acre is 1.27 English acres.  

Arpent - Unit of length and area used in France, Louisiana, and Canada. As a unit of length, approximately 191.8 feet (180 old French 'pied', or foot). The (square) arpent is a unit of area, approximately .845 acres, or 36,802 square feet. 

Chain - Unit of length usually understood to be Gunter's chain, but possibly variant by locale. Chains equal to 2 poles (one half the standard length) are found in Virginia. The name comes from the heavy metal chain of 100 links that was used by surveyors to measure property bounds. 

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

Furlong - Unit of length equal to 220 yards. Its name derives from "furrow long", the length of a furrow. 
 

Gunter's Chain - Unit of length equal to 66 feet, or 4 poles. This unit was apparently defined as one tenth of a furlong, a common unit of length in the old days. The mile was redefined from the old Roman value of 5000 feet to 5280 feet in order to be an even multiple 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.

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).

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

Morgen - Unit of area equal to about .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.

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, equal to 16.5 feet. A mile is 320 poles. As a unit of area, 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. 

Rod - See pole 

. 
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. 


Surveying Terms   

Aliquot - The description of fractional section ownership used in the public land states. A parcel is generally identified by its section, township, and range. The aliquot specifies its precise location within the section, for example, the northwest quarter of the southeast quarter. 

Benchmark - A survey mark made on a monument having a known location and elevation, serving as a reference point for surveying. 

Call - Any feature, landmark, or measurement called out in a survey. For example, "two white oaks next to the creek" is a call. 

Chain carrier - An assistant to the surveyor, the chain carriers moved the surveying chain from one location to another under the direction of the surveyor. This was a position of some responsibility, and the chain carriers took an oath as "sworn chain carriers" that they would do their job properly. 

Condition - See Conditional line. 

Conditional line - An agreed line between neighbors that has not been surveyed, or which has been surveyed but not granted. 

Corner - The beginning or end point of any survey line. The term corner does not imply the property was in any way square. 

Declination - The difference between magnetic north and geographic (true) north. Surveyors used a compass to determine the direction of survey lines. Compasses point to magnetic north, rather than true north. This declination error is measured in degrees, and can range from a few degrees to ten degrees or more. Surveyors may have been instructed to correct their surveys by a particular declination value. The value of declination at any point on the earth is constantly changing because the location of magnetic north is drifting. More information about historical values of declination is available. 

First station - See Point of Beginning

Gore - A thin triangular piece of land, the boundaries of which are defined by surveys of adjacent properties. Loosely, an overlap or gap between properties.

Landmark - A survey mark made on a 'permanent' feature of the land such as a tree, pile of stones, etc. 
 

Line Tree - Any tree that is on a property line, specifically one that is also a corner to another property. 
 

Meander - "with the meanders of the stream" means the survey line follows the twists and turns of the stream. 
 

Merestone - A stone that marks a boundary. See monument. 
 

Monument - A permanently placed survey marker such as a stone shaft sunk into the ground. 
 

Out - An 'out' was ten chains. When counting out long lines, the chain carriers would put a stake at the end of a chain, move the chain and put a stake at the end, and so on until they ran "out" of ten stakes.

Point of Beginning - The starting point of the survey 
 

Plat - A drawing of a parcel of land. 
 

Witness Tree - Generally used in the U.S. public land states, this refers to the trees close to a section corner. The surveyor blazed them and noted their position relative to the corner in his notebook. Witness trees are used as evidence for the corner location. 

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