Gunter Chain / Surveyor's Chain







“What is the length of cricket pitch?”

 “It is equal to 22 yards”.


Cricket is a bat-and-ball game played between two teams of eleven players on a field at the center of which is a 22 yard pitch with a wicket at each end, each comprising two bails balanced on three stumps. 



Recalling the memories of childhood, we use to place the wickets by pacing out a distance of 22 paces by walking. At that time, we were not aware neither interested to know the exact length of cricket pitch. But this time, the question raised in my mind that why it is 22 yards!! ?? Why it is not like 22 meters or 25 yards or 20 yards?


Cricket Pitch
Cricket Pitch


The standard length of cricket pitch is simply one Gunter chain (Surveyor’s chain) since the first known code of Laws in 1744 and it is believed this length had been in use since the introduction of Gunter's chain  in 1620.

Throughout recorded history surveyors have used many devices for measuring distances such as rope, poles, grape vines, pacing, chains etc. Gunter Chain (also termed as Surveyors chain) was invented by well known English mathematician and astronomer in 1620. The chain was 66 feet long divided into 100 links made of steel, with round handles at either end. The chain was marked off into groups of 10 links by brass rings or tags which simplify intermediate measurement. Each link is thus 7.92 inches.

Gunter Chain & Tags
Gunter Chain & Tags

Gunter Chain
Gunter Chain

The basic "Gunter's" chain was the primary tool of surveyors to measure distance during Chain Surveying. Chain surveying is the type of surveying in which only linear measurements are made in the field. The main principle of chain surveying or chain triangulation is to provide a framework consist of number of well-conditioned triangles or nearly equilateral triangles. It is used to find the area of the field.

One chain = 22 Yards = 66 Feet.
Where
One yard = 3 Feet.

The Great Trigonometric Survey Of India begun in 1802 by the infantry officer William Lambton, under the auspices of the East India Company. Long baselines ranges from 5 to 10 miles were measured using Chains. The surveyors used to stretch a chain on coffers supporting on pickets. The chain is housed under shade to reduce errors due to thermal expansion. The alignment of the chain is controlled using a boning telescope. A sketch below portrays the measurement of the Calcutta baseline in 1832. 

Culcutta Base Line - Great Trigonometric Survey Of India
Culcutta Base Line - Great Trigonometric Survey Of India


Apart from the feet and yards, there are further linear units which are multiples of chains.
Unit
Chains
Feet
Yards
Rod/Perch/Pole
0.25
16.5
5.5
Furlong
10
660
220
Mile
80
5280
1760
League
240
15840
5280

Similarly, acre, the well known unit of area is also based on Gunter chain. It is traditionally defined as the area of one chain by one furlong (66 by 660 feet), which is exactly equal to 10 square chains, 1/640 of a square mile, or 43,560 square feet.


Comments

  1. Emonefe (CADGIS WHATSAPP GROUP)9 March 2020 at 02:51

    Thanks so much for the nice write up. The synergy between cricket game and the chain surveying. I thought chain surveying was for linear boundary delineation only not until now. Thanks

    ReplyDelete

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