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Although link chains were later superseded by the steel ribbon tape (a form of tape measure), its legacy was a new statutory unit of length called the chain, equal to 22 yards (66 feet) of 100 links. [8] This unit still exists as a location identifier on British railways, as well as all across America in what is called the public land survey ...
Even so, the Mendenhall Order length of the yard continues in use even in 2013 in the United States as the basis for the survey foot. The prior land survey data for North America of 1927 (NAD27) had been based on the survey foot, and a new triangulation based on the metric system (NAD83) was not released until 1986.
The rod, perch, or pole (sometimes also lug) is a surveyor's tool [1] and unit of length of various historical definitions. In British imperial and US customary units, it is defined as 16 + 1 ⁄ 2 feet, equal to exactly 1 ⁄ 320 of a mile, or 5 + 1 ⁄ 2 yards (a quarter of a surveyor's chain), and is exactly 5.0292 meters.
A standard chord length is used: in the UK this is conventionally 30 metres, or sometimes 20 metres. Half chords, i.e. 15 metre or 10 metre intervals, are marked on the datum rail using chalk. The string, which is one full chord long, is then held taut with one end on two marks at each end of a chord, and the offset at the half chord mark measured.
This 1988 BLM map depicts the principal meridians and baselines used for surveying states (colored) in the Public Land Survey System. The Public Land Survey System (PLSS) is the surveying method developed and used in the United States to plat, or divide, real property for sale and settling.
C L is the corrected length of the line to be measured or laid out; M L is the measured length or length to be laid out; N L is the nominal length of the tape as specified by its mark; K L is a known length; Corr is the ratio of measured to actual length , determined by measuring a known length.
The chain is the unit of linear measurement for the survey of the public lands as prescribed by law. All returns of measurement in the rectangular system are made in the true horizontal distance in links, chains, and miles. The only exceptions to this rule are special requirements for measurement in feet in mineral surveys and townsite surveys ...
Traverse networks involve placing survey stations along a line or path of travel, and then using the previously surveyed points as a base for observing the next point. Connected survey lines form the framework and the directions and lengths of the survey lines are measured with an angle measuring instrument and tape or chain. [2]