Point of Beginning

Web Exclusive! The Surveyors Rod

November 25, 2002
An often repeated and published myth within the surveying profession concerns the origin of the measuring tool known as the rod. The surveyor’s rod, also known as a pole or a perch, is a particularly important piece of material culture. Essentially a long wooden staff of 16 1/2 English feet, this standardized length allowed early surveyors to measure distances accurately. More importantly, this length was the basis of a system of area calculation that also allowed the early surveyor to very accurately lay out a specified area of land without complicated calculation. This particular length of 16 1/2 feet has had an enormous influence on surveying and land development, although the rod itself has not been in common use for over two centuries.

The classic text Boundary Control and Legal Principles by Brown, et al. (1986:30), notes that in the 16th century, the rod was established as the length of the left feet of the first 16 men out of church one Sunday morning. Brown cites, "The Amazing Story of Measurements." This same story is often repeated in surveying texts and publications. Indeed, it is a part of the folklore of the surveying profession.

While the story that the rod was originally meant to represent 16 human feet is probably true, the reality is that the rod had been in common use many centuries earlier than Brown suggested. As early as 1270, Edward I of England issued a Royal ordinance titled “Assize of Weights and Measures,” which at this date defined into law the length of a “Perch.” This indicates that the perch was in use prior to this time. (1,4,5)

Usually, a larger measurement is defined in terms of being an equal number of a smaller measurement, much in the sense that one pound is considered to be 16 ounces. And yet as early as 1270, the perch is not considered as 16 feet but rather specifically defined as 16 1/2 feet. This is a critical point to consider when attempting to date the origins of the rod itself. The parties who considered this issue in the 1270s were actually unwilling to define the pole in terms of an even number of feet. It is as if that even by this early date, a pole of a particular length, an inconvenient 16 1/2 English feet, had been established for so long that it was not considered feasible to define it otherwise.

It is worth special note that the English rod or perch is within .03 feet of equaling 16 old Danish “fods,” and is within a similar tolerance to equaling 16 old Prussian “Rheinfuss” (7), both of which are lengths of measure slightly longer than, but no doubt corresponding in origin with, the English foot. We can therefore speculate, but not document, that the origin of the rod may go back as far as the Germanic Invasions of England around the 9th century, when the rod may well have equaled 16 “fods.” Several scholars have noted that the old North German land measure of 16 Rhineland feet, the “ruthen,” is similar to the rod in length and may have been introduced into England by the Saxons (Berriman 1953; Richeson 1965:16-18,250. The use of the term perch for this tool is most likely derived from the Latin word “Pertica.”(Taylor 1947:128).

Use of the Pole as an Area Calculator

The use of the pole as a calculator for land area clearly was standardized by the early 14th century and probably well before that period. Again under Edward I, an act of English Law in 1305 defined an acre of land as 160 square perches, and defines a perch as 3.5 yards. This standardization allowed early surveyors to easily lay out parcels of land with a specified area. An acre could be a rectangle of 20 poles x 8 poles, for instance, or 10 x 16 if desired. Again note how the land is defined in terms of an even number of perches, but the uneven value of the perch in terms of the smaller “yard” is identified and maintained.

It is, therefore, very likely that the perch had been so long established by the early 14th century that it would have been impractical to change it — even by this early date. Subsequently, however, all lengths of measure longer than the perch were redefined in terms of the perch. An Act of Elizabeth I in the year 1592 reads, “A mile shall contain 8 furlongs, every furlong 40 poles, and every pole shall contain 16 feet and a half.” (Berryman 1953:170; Zupko 1985:309).

The rod, therefore, represents the oldest standard measure of length in the English system. The foot did change from the longer Germanic definition into a shorter English definition. But the length of the rod was kept static. Indeed, the old Roman term “mile,” or 1,000 strides, was redefined as 320 poles and the old Roman term “acre” was defined as 160 square poles. While most modern surveyors associate early distance measuring with the 66-foot Gunter’s Chain, invented in the 17th century, (Denny 1996; Richeson 1966:108-109) it is clear that the chain was simply a new device of efficient choice for surveying in a system devised and perfected centuries before, based upon the standard rod.

With the rod, the surveyor had the ability to efficiently measure and accurately lay out specified areas, both small lots and large acreage and to measure lengthy distances. This surveying system became firmly established with agrarian land reforms in 16th century England (Darby 1933; Richeson 1966; Taylor 1930; 140-161). By the time of the English settlement of North America, this system had been established and evolving for over 300 years.

The length of a mile and the size of an acre are values that many people can almost visualize. Both of these values are based on the length of the rod. By extension, the size of a standard township, and of the sections within the township, are also based on the length of this rod. As a object of material culture, the surveyor’s rod of 16 1/2 feet, a value expressed in wood, standardized over 700 years ago, has certainly withstood the test of time.

References Cited:

(1) Berriman, A.E.
1953 Historical Metrology, J.M. Dent and Sons, LTD, London

(2) Brown, Curtis M., et al.
1986 Boundary Control and Legal Principles, Third Edition, John Wiley and Sons, New York

(3) Denny, Milton E.
1996 The Making of a Chain, Point of Beginning, May 1996, 21(6):58-59

(4) Nicholson, Edward
1912 Men and Measures, A History of Weights and Measures, Ancient and Modern, Smith, Elder & Co., London

(5) Richeson, A.W.
1966 English Land Measuring to 1800: Instruments and Practices, The Massachusetts Institue of Technology Press, Cambridge.

(6) Taylor, E.G.R.
1930 Tudor Geography, 1485-1583, Methuen & Co., Ltd., London.

(7) Zupko, Ronald Edward
1977 British Weights and Measures, A History from Antiquity to the Seventeenth Century. The University of Wisconsin Press, Madison

(8) 1985 A Dictionary of Weights and Measures for the British Isles: The Middle Ages to the Twentieth Century.
American Philosophical Society, Philadelphia.