A hectare is defined as ten thousand square meters. Since one meter is about 39.4 inches, one can use these numbers, along with the definition of an acre as 43,650 square feet, to find that one hectare is equal to 2.471 acres. Because a hectare is defined by using meters, we see that it is a relatively modern definition with a solid foundation. Next, a trick question for you. Which is larger, a hectare or an acre?
The books written specifically for surveyors in the Sixteenth and Seventeenth Centuries are guides to the changing nature of the profession. They chart the shifting focus of a surveyor’s duties and illustrate the difficulties to be overcome before scientific land mensuration was possible. The many pages devoted to basic instruction in mathematics testify to the paucity of formal education relevant to training surveyors. Sixteenth Century books often also included tables to assist those who could not multiply, divide, or use fractions. Even as late as 1688, John Love’s " Geodaesia " devoted over one-fourth of its pages to instruction in " vulgar arithmetick ", basic geometry, conversion of one unit of linear measure to another, and calculation of superficial areas.
Authors in this period found it necessary to refute prevalent false notions of geometry. Among the common errors were the assumptions that all four sided figures had right angles and the belief that the area of a field of irregular shape could be computed by adding the lengths of all sides, dividing by four, and squaring the result. (This practice was equivalent to finding the average length of a side and multiplying it by itself as though the field were a square.)
Before 1550, English surveyors relied upon wooden rods or knotted cords (treated with wax and rosin to limit stretching and shrinking) to survey by line-measurements only. No angle-measuring instruments were used. Though small pocket magnetic compasses were available, their use was apparently limited to providing orientations in poor weather. Field notes were kept on notched sticks or stray sheets of paper. No plots were drawn of the boundaries.
In the next seventy years after 1550, enormous progress was made in the construction of instruments and in the perfection of techniques for measuring in the field. These new instruments permitted the measurement of angles and the sighting of a straight line. Many of these were borrowed from navigators and astronomers, who in turn had borrowed heavily from the Arabs. The technicians at work in Germany, France, and Italy were ahead of the English.
When angles were first measured, the unit was not degrees but the directions of the wind as northeast or east by northeast. The circle was divided into thirty-two parts, eight to each 90-degree sector. Again, we see the borrowing of techniques from the mariners.
(02 Mar 05)
We gratefully acknowledge the work of John Blankenbaker who published over 2,500 Germanna History Notes via the Germanna-L@rootsweb.com email list from 1997 to 2008. We are equally thankful to George Durman (Sgt. George) for hosting the list and republishing the notes via rootsweb.com.