Rod (unit)

Not to be confused with a surveyor's pole, upon which a survey instrument is mounted; a ranging rod used for sighting; or, a level staff, which may also be called a leveling rod.

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. The rod is useful as a unit of length because integer multiples of it can form one acre of square measure (area). The 'perfect acre'^[2] is a rectangular area of 43,560 square feet, bounded by sides 660 feet (a furlong) long and 66 feet (a chain) wide (220 yards by 22 yards) or, equivalently, 40 rods by 4 rods. An acre is therefore 160 square rods or 10 square chains.

rod
Unit system	imperial/US units
Unit of	length
Conversions
1 rod in ...	... is equal to ...
Imperial/US units	16+1⁄2 ft
metric (SI) units	5.0292 m

The name perch derives from the Ancient Roman unit, the pertica. The measure also has a relationship with the military pike of about the same size. Both measures^[1] date from the sixteenth century,^[3] when the pike was still utilized in national armies. The tool has been supplanted, first by steel tapes and later by electronic tools such as surveyor lasers and optical target devices for surveying lands. In dialectal English, the term lug has also been used, although the Oxford English Dictionary states that this unit, while usually of 16+1⁄2 feet, may also be of 15, 18, 20, or 21 feet.^[4][5][6]

In the United States until 1 January 2023, the rod was often defined as 16.5 US survey feet, or approximately 5.029 210 058 m.^[7]

History

The sign included in Pieter Aertsen's painting A Meat Stall with the Holy Family Giving Alms reads in Flemish: "behind here are 154 rods of land for sale immediately, either by the rod according to your convenience or all at once".

In England, the perch was officially discouraged in favour of the rod as early as the 15th century;^{[8][better source needed]} however, local customs maintained its use. In the 13th century, perches were variously recorded in lengths of 18 feet (5.49 m), 20 feet (6.1 m), 22 feet (6.71 m) and 24 feet (7.32 m); and even as late as 1820, a House of Commons report notes lengths of 16+1⁄2 feet (5.03 m), 18 feet (5.49 m), 21 feet (6.4 m), 24 feet (7.32 m), and even 25 feet (7.62 m).^[9] In Ireland, a perch was standardized at 21 feet (6.4 m), making an Irish chain, furlong and mile proportionately longer by 27.27% than the "standard" English measure.^[10]

Until English King Henry VIII seized the lands of the Roman Catholic Church in 1536,^[1] land measures as we now know them were essentially unknown.^[1] Instead a narrative system of landmarks and lists was used. Henry wanted to raise even more funds for his wars than he'd seized directly from church property (he'd also assumed the debts of the monasteries^[1]), and as James Burke writes and quotes in the book Connections that the English monk Richard Benese "produced a book on how to survey land using the simple tools of the time, a rod with cord carrying knots at certain intervals, waxed and resined against wet weather." Benese poetically described the measure of an acre in terms of a perch:^[3]

an acre bothe of woodlande, also of fyldlande [heath] is always forty perches in length, and four perches in breadth, though an acre of woodlande be more in quantitie [value, i.e. was more valued commercially] than an acre of fyldelande

The practice of using surveyor's chains, and perch-length rods made into a detachable stiff chain, came about a century later when iron was a more plentiful and common material. A chain is a larger unit of length measuring 66 feet (20.1168 m), or 22 yards, or 100 links,^[11] or 4 rods (20.1168 meters). There are 10 chains or 40 rods in a furlong (eighth-mile), and so 80 chains or 320 rods in one statute mile (1760 yards, 1609.344 m, 1.609344 km); the definition of which was legally set in 1593 and popularized by Royal surveyor (called the 'sworn viewer'^[12]) John Ogilby only after the Great Fire of London (1666).

An acre is defined as the area of 10 square chains (that is, an area of one chain by one furlong), and derives from the shapes of new-tech plows^[2] and the desire to quickly survey seized church lands into a quantity of squares for quick sales^[3] by Henry VIII's agents; buyers simply wanted to know what they were buying whereas Henry was raising cash for wars against Scotland and France.^[3] Consequently, the surveyor's chain and surveyor rods or poles (the perch) have been used for several centuries in Britain and in many other countries influenced by British practices such as North America and Australia. By the time of the industrial revolution and the quickening of land sales, canal and railway surveys, et al. Surveyor rods such as used by George Washington were generally made of dimensionally stable metal—semi-flexible drawn wrought iron linkable bar stock (not steel), such that the four folded elements of a chain were easily transportable through brush and branches when carried by a single man of a surveyor's crew. With a direct ratio to the length of a surveyor's chain and the sides of both an acre and a square (mile), they were common tools used by surveyors, if only to lay out a known plottable baseline in rough terrain thereafter serving as the reference line for instrumental (theodolite) triangulations.

The rod as a survey measure was standardized by Edmund Gunter in England in 1607 as a quarter of a chain (of 66 feet (20.12 m)), or 16+1⁄2 feet (5.03 m) long.

In ancient cultures

The perch (pertica) as a lineal measure in Rome (also decempeda) was 10 Roman feet (2.96 metres), and in France varied from 10 feet (perche romanie) to 22 feet (perche d'arpent—apparently 1⁄10 of "the range of an arrow"—about 220 feet). To confuse matters further, by ancient Roman definition, an arpent equalled 120 Roman feet. The related unit of square measure was the scrupulum or decempeda quadrata, equivalent to about 8.76 m² (94.3 sq ft).^[13]

In continental Europe

A standard at the City Hall in Münster, Germany from 1816; the bar shown is one "Prussian Half Rod" (1.883 m) long.

Units comparable to the perch, pole or rod were used in many European countries, with names that include French: perche and canne, German: Ruthe, Italian: canna and pertica, Polish: pręt and Spanish: canna. They were subdivided in many different ways, and were of many different lengths.

Rods and similar units in continental Europe^{[dubious – discuss]}

Place	Local name	Local equivalent	Metric equivalent (meters)
Aachen	Feldmeßruthe	16 Fuß	4.512[14]
Amsterdam	Roede	13 Voet	3.681[15]
Aubenas, Ardèche	canne	8 pans	1.985[14]
Baden, Grand Duchy of	Ruthe	10 Fuß	3.0[14]
Basel, Canton of	Ruthe	16 Fuß	4.864[14]
Bern, Canton of	Ruthe	10 Fuß	2.932[14]
Barcelona	canna	8 palmos	1.581[14]
Braunschweig	Ruthe	16 Fuß	4.565[14]
Bremen	Ruthe	8 Ellen or 16 Fuß	4.626[14]
Brussels	Ruthe	20 Fuß	4.654[14]
Cagliari, Sardinia	canna	10 palmi	2.322[14]
Calenberg Land	Ruthe	16 Fuß	4.677[14]
Cassel, Hessen	Ruthe	14 Fuß	4.026[14]
Denmark	Ruthe	10 Fuß	3.138[14]
Canton of Geneva	Ruthe	8 Fuß	2.598[14]
Hamburg	Geestruthe	16 Fuß	4.583[14]
Hamburg	Marschruthe	14 Fuß	4.010[14]
Hannover	Ruthe	16 Fuß	4.671[14]
France	Perche	3 toises	5.847[14]
France	Perche (for woodland)	3+2⁄3 toises	7.145[14]
Genoa	canna	10 palmi	2.5[14]
Jever, Oldenburg	Ruthe	20 Fuß	4.377[14]
Mallorca	canna	8 palmos	1.714[14]
Malta	canna	8 palmi	2.08[14]
Mecklenburg	Ruthe	16 Fuß	4.655[14]
Menorca, but not Mahón	canna		1.599[14]
Menorca, city of Mahon	canna	8 palmos	1.714[14]
Messina, Sicily	canna	8 palmi	2.113[14]
Montauban, Tarn-et-Garonne	canne	8 pans	1.783[14]
Morocco	canna	8 palmos	1.714[14]
Naples	canna (for cloth)	8 palmi
Naples, Kingdom of: Apulia, Calabria, Eboli, Foggia, Lucera	percha	7 palmi	1.838[14]
Naples, Kingdom of: Capua	percha	7+1⁄5 palmi	1.892[14]
Naples, Kingdom of: Fiano, Naples	percha	7+1⁄2 palmi	2.014[14]
Naples, Kingdom of: Caggiano, Cava, Nocera, Rocce, Salerno	percha	7+2⁄3 palmi	1.971[14]
Nuremberg, Bavaria	Ruthe	16 Fuß	4.861[14]
Oldenburg	Ruthe	20 Fuß	5.927[14]
Palermo, Sicily	canna	8 palmi	1.942[14]
Parma	Pertica	6 bracci	3.25[14]
Poland	Pręt	7+1⁄2 łokci or 10 pręcików	4.320[14]
Prussia, Rheinland	Ruthe	12 Fuß	3.766[14]
Rijnland	Roede	12 Voet	3.767[15]
Rome	canna (for cloth)		2[14]
Rome	canna (for building)		2.234[14]
Saragoza	canna		2.043[14]
Saxony	Ruthe	16 Leipziger Fuß	4.512[14]
Sweden	Ruthe	16 Fuß	4.748[14]
Tortosa	canna		1.7[14]
Tuscany, Grand-Duchy of (Florence, Pisa)	canna	5 bracci	2.918[14]
Uzès, Gard	canne	8 pans	1.98[14]
Waadt, Canton of	Ruthe or toise courante	10 Fuß	3[14]
Württemberg	Reichsruthe	10 Fuß	2.865[14]
Württemberg	old Ruthe	16 Fuß	4.583[14]
Venice, Republic of	Pertica	6 piedi	2.084[14]
Zürich, Canton of	Ruthe	10 Fuß	3.009[14]

In Britain and Ireland

Land for sale in Gortavaura, County Galway, Ireland: the area is 48 acres, 3 roods and 29 perches. In metric units, this is 19.8 hectares.

In England, the rod or perch was first defined in law by the Composition of Yards and Perches, one of the statutes of uncertain date from the late 13th to early 14th centuries: tres pedes faciunt ulnam, quinque ulne & dimidia faciunt perticam (three feet make a yard, five and a half yards make a perch).^[16]

The length of the chain was standardized in 1620 by Edmund Gunter at exactly four rods.^[17][18] Fields were measured in acres, which were one chain (four rods) by one furlong (in the United Kingdom, ten chains).^[19]

Bars of metal one rod long were used as standards of length when surveying land. The rod was still in use as a common unit of measurement in the mid-19th century, when Henry David Thoreau used it frequently when describing distances in his work, Walden.^[20]

In traditional Scottish units, a Scottish rood (ruid in Lowland Scots, ròd in Scottish Gaelic), also fall measures 222 inches (6 ells).^[21]

Modern use

The rod was phased out as a legal unit of measurement in the United Kingdom as part of a ten-year metrication process that began on 24 May 1965.^[22]

Sign near a historic site in Indiana, with its location given as "80 rods east", equivalent to roughly 400 m or 1⁄4 mile.

In the United States, the rod, along with the chain, furlong, and statute mile (as well as the survey inch and survey foot) were based on the pre-1959 values for United States customary units of linear measurement until 1 January 2023. The Mendenhall Order of 1893 defined the yard as exactly 3600⁄3937 meters, with all other units of linear measurement, including the rod, based on the yard. In 1959, an international agreement (the international yard and pound agreement), defined the yard as the fundamental unit of length in the Imperial/USCU system, defined as exactly 0.9144 metres. However, the above-noted units, when used in surveying, may retain their pre-1959 values, depending on the legislation in each state. The U.S. National Geodetic Survey and National Institute of Standards and Technology have replaced the definition for the above-mentioned units by the international 1959 definition of the foot, being exactly 0.3048 meters.^[23][24]

Despite no longer being in widespread use, the rod is still employed in certain specialized fields. In recreational canoeing, maps measure portages (overland paths where canoes must be carried) in rods; typical canoes are approximately one rod long.^[25] The term is also in widespread use in the acquisition of pipeline easements, as the offers for an easement are often expressed on a "price per rod".^[26]

In the United Kingdom, the sizes of allotment gardens continue to be measured in square poles in some areas, sometimes being referred to simply as poles rather than square poles.^[27]

In Vermont, the default right-of-way width of state and town highways and trails is three rods 49 ft 6 in (15.09 m).^[28] Rods can also be found on the older legal descriptions of tracts of land in the United States, following the "metes and bounds" method of land survey;^[29] as shown in this actual legal description of rural real estate:

LEGAL DESCRIPTION: Commencing 45 rods East and 44 rods North of Southwest corner of Southwest 1/4 of Southwest 1/4; thence North 36 rods; thence East 35 rods; thence South 36 rods; thence West 35 rods to the place of beginning, Manistique Township, Schoolcraft County, Michigan.^[30]

Area and volume

The terms pole, perch, rod and rood have been used as units of area, and perch is also used as a unit of volume. As a unit of area, a square perch (the perch being standardized to equal 16+1⁄2 feet, or 5+1⁄2 yards) is equal to a square rod, 30+1⁄4 square yards (25.29 square metres) or 1⁄160 acre. There are 40 square perches to a rood (for example a rectangular area of 40 rods times one rod), and 160 square perches to an acre (for example a rectangular area of 40 rods times 4 rods). This unit is usually referred to as a perch or pole even though square perch and square pole were the more precise terms. Rod was also sometimes used as a unit of area to refer to a rood.

However, in the traditional French-based system in some countries, 1 square perche is 42.21 square metres.

As of August 2013, perches and roods are used as government survey units in Jamaica.^{[citation needed]} They appear on most property title documents. The perch is also in extensive use in Sri Lanka, being favored even over the rood and acre in real estate listings there.^[31] Perches were informally used as a measure in Queensland real estate until the early 21st century, mostly for historical gazetted properties in older suburbs.^[32]

Volume

A traditional unit of volume for stone and other masonry. A perch of masonry is the volume of a stone wall one perch (16+1⁄2 feet or 5.03 metres) long, 18 inches (45.7 cm) high, and 12 inches (30.5 cm) thick. This is equivalent to exactly 24+3⁄4 cubic feet (0.92 cubic yards; 0.70 cubic metres; 700 litres).

There are two different measurements for a perch depending on the type of masonry that is being built:

1. A dressed stone work is measured by the 24+3⁄4-cubic foot perch (16+1⁄2 feet or 5.03 metres) long, 18 inches (45.7 cm) high, and 12 inches (30.5 cm) thick. This is equivalent to exactly 24+3⁄4 cubic feet (0.916667 cubic yards; 0.700842 cubic metres).
2. a brick work or rubble wall made of broken stone of irregular size, shape and texture, made of undressed stone, is measured by the (16+1⁄2 feet or 5.03 metres) long, 12 inches (30.5 cm) high, and 12 inches (30.5 cm) thick. This is equivalent to exactly 16+1⁄2 cubic feet (0.611111 cubic yards; 0.467228 cubic metres).^[33]

See also

• Anthropic units
• English units

References

1. Burke, James (1978). "Chapter 9". Connections: Alternative History of Technology. Macmillan. p. 304. ISBN 978-0-333-29066-8.
2. Connections, pbk. p.63
3. Connections, pbk. p.263
4. Bonten, JHM (19 January 2007). "Anglo-Saxon and Biblical to Metrics Conversions". Surveyor + Chain + British-Nautical. Retrieved 1 November 2010.
5. Rowlett, Russ (15 December 2008). "lug [1]". How Many? A Dictionary of Units of Measurement. University of North Carolina at Chapel Hill. Retrieved 1 November 2010.
6. "lug, n.1". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
7. "U.S. Survey Foot: Revised Unit Conversion Factors". National Institute of Standards and Technology. 23 September 2019. Retrieved 3 January 2023.
8. Encyclopædia Britannica, English measure
9. House of Commons Report (Second) of Commissioners to Consider the Subject of Weights and Measures. Parliamentary Papers. Vol. HC314. 13 July 1820. pp. 473–512.
10. "Units: P". unc.edu.
11. Kirkpatrick, Elizabeth Mclaren (1990). The Cassell English Dictionary. London. p. 214. ISBN 0-304-34003-0.{{cite book}}: CS1 maint: location missing publisher (link)
12. "Connections", pbk. p.265
13. Smith, Sir William & Anthon, Charles (1851). A new classical dictionary of Greek and Roman biography, mythology, and geography partly based upon the Dictionary of Greek and Roman biography and mythology. New York: Harper & Bros. pp. 1024–1030.
14. Niemann, Friedrich (1830). Vollständiges Handbuch der Münzen, Masse, und Gewichte aller Länder der Erde fur Kaufleute, Banquiers ... in alphabetischer Ordnung [Complete handbook of coins, measures and weights of all countries in the world for merchants, bankers ... in alphabetical order] (in German). Quedlinburg und Leipzig: Gottfr. Basse. pp. 231–232, 286.
15. de Gelder, Jacob (1824). Allereerste Gronden der Cijferkunst [Introduction to Arithmetic] (in Dutch). ’s-Gravenhage (The Hague) and Amsterdam: de Gebroeders van Cleef. pp. 163–176. Retrieved 13 June 2017.
16. The statutes at large (in Latin). London: Charles Eyre & Andrew Strahan. 1794. p. 200.
17. Taylor, Thomas Ulvan (1908). "Chapter 1". Surveyor's hand book. McGraw-Hill. p. 1. Retrieved 28 November 2011.
18. Russell, Jeffrey S.; American Society of Civil Engineers (1 August 2003). Perspectives in civil engineering: commemorating the 150th anniversary of the American Society of Civil Engineers. ASCE Publications. p. 167. ISBN 978-0-7844-0686-1. Retrieved 28 November 2011.
19. Rowlett, Russ (3 December 2008). "acre (ac or A)". How Many? A Dictionary of Units of Measurement. University of North Carolina at Chapel Hill. Archived from the original on 20 December 2008. Retrieved 1 November 2010.
20. Thoreau, Henry David (1899). Walden: or, Life in the woods. H. Altemus. pp. 67, 113, 203, 204, 208, 290, 300, 309, 319, 339, 341, 356. Retrieved 27 November 2011.
21. ""fall, faw"". Dictionary of the Scottish Language – Dictionary of the Older Scottish Tongue.
22. Consumer and Competition Policy Directorate (1968). Report (1968) by the Standing Joint Committee on Metrication (PDF) (Report). Department of Trade and Industry. Archived from the original (PDF) on 25 June 2008. Retrieved 1 November 2010. {{cite report}}: |author= has generic name (help)
23. "NGS and NIST to Retire U.S. Survey Foot after 2022". National Geodetic Survey. 31 October 2019. Retrieved 4 March 2020.
24. "U.S. Survey Foot: Revised Unit Conversion Factors". NIST. 16 October 2019. Retrieved 4 March 2020.
25. "Canoe Glossary and Clickable Canoe". OutdoorPlaces.com. Michael Thiessen. Retrieved 1 November 2010.
26. "Pipeline Terms and Addendum". The Clark Law Firm. Archived from the original on 8 March 2015. Retrieved 24 October 2012.
27. "Allotments". Watford Borough Council. Archived from the original on 14 August 2009. Retrieved 5 October 2009.
28. "19 V.S.A. § 702: Width of highways and trails". The Vermont Statutes Online. Vermont General Assembly.
29. Shelton, Neil. "How to Read Land Descriptions". homestead.org. p. 5. Retrieved 7 May 2008.
30. "Lake View Parcel $198 Down $198 Month Incredible 8 Acre Parcel!". EagleStar. American Eagle Star. Retrieved 1 November 2010.
31. "Land For Sale". Sri Lanka Property Market. Archived from the original on 24 January 2018.
32. "Dutton Park real estate agent Archives". Bees Nees.
33. See McClurg, William M. & Shoemaker, Morrell M. (1970). The Building Estimator's Reference Handbook (17th ed.). Chicago: Frank R. Walker Company. p. 1644.