The transit and tape permitted more precise measurements necessary in land surveying. The steel tape, usually 100 or 200 feet long and graduated in hundredths of a foot, provided an accuracy significantly greater than the Gunter’s Chain. While the compass was generally only able to measure the magnetic bearing of a line to the nearest one-quarter degree, a transit is able to measure the angles between lines to less than one minute of an arc. These early surveying tools were not very precise, but were sufficient in the days when land values were 50 cents per acre, or less.Įventually the use of the compass gave way to the transit, and the chain to the steel tape. The compass was either mounted on a tripod or a single pole, called a “Jacob Staff”. Other early units of measurement were called “rods” or “poles”, representing 16.5 feet for each unit. The modern steel and fiberglass measuring tapes used by surveyors are still referred to as “chains” in deference to these early methods of surveying. These units of measurement can still be found in many older deeds on record at the courthouse. 1 link is equal to 1/100 of a chain or 7.92 inches. The most common surveyor’s chain was 66 feet long and made up of 100 links. Old time surveyor with stadia rod transit and tape.įrom colonial times, though the 1800’s, surveying in this country was performed using a crude transit or a compass and a “chain”. The first person recorded to have used the compass as a navigational aid was Zheng He (1371-1435), from the Yunnan province in China, who made seven ocean voyages between 14. Magnetized needles used as direction pointers instead of the spoon-shaped lodestones appeared in the 8th century AD,again in China, and between 8 they seemed to have become common as navigational devices on ships. The pointing needle was a lodestone spoon-shaped device, with a handle that would always point south. They designed the compass on a square slab which had markings for the cardinal points and the constellations. Chinese fortune tellers used lodestones (a mineral composed of an iron oxide which aligns itself in a north-south direction) to construct their fortune telling boards.Įventually someone noticed that the lodestones were better at pointing out real directions, leading to the first compasses. The compass was probably invented by the Chinese during the Quin dynasty (221-206 BC). The magnetic compass is one of the most important instruments in the history of surveying. The plumb bob is still an indispensable tool in modern construction. But there is one thing the level can’t do easily, and that is to transfer an exact point from one height to another. It is quicker and easier to use and just as accurate. For establishing plumb and true horizontal the level is simply a better tool. The invention of the spirit level, and the beginnings of the Industrial Revolution that allowed the level to be manufactured, both accurately and cheaply, began the demise of the ancient plumb tools. These simplest of tools remained virtually unchanged for the next 4400+ years. These earliest bobs were stone and their shape, although often egg-like, really didn’t matter. The worker could then make a more precise visual judgement as to the trueness of plumb horizontal level. This was the first of the plumb bob, against a wood frame that paralleled the surface being measured. This observation made the plumb bob the earliest surveying instrument.īy 2600 BC, we know the Egyptians had taken this concept and created the earliest surveying instruments: the plumb board, the A-Level, T-Level and plumb square. The observation that a heavy object hanging from a string causes the string to hang perpendicular to the earth is easily made. ![]() Surveying is still the sign of progress in the development and use of the earth’s resources.Ī plumb, a square, and a square level from the tomb of Senedjem ![]() More recently, the large volume of general construction, numerous land subdivisions with better records required, and demands posed by the fields of exploration and ecology have entailed an augmented surveying program. Increased land values and the importance of exact boundaries, along with the demand for public improvements in the canal, turnpike, and railroad eras, bought surveing into a prominent position. Later its activities were expanded to include establishment of control monuments throughout the country. Initially its charge was to perform hydrographic surveys and prepare nautical charts. Coast and Geodetic Survey was established by an act of Congress in 1807. The need for maps and location of national boundaries caused England and France to make extensive surveys requiring accurate triangulation thus geodetic surveying began. In the 18th and 19th centuries the art of surveying advanced more rapidly. Geodesy (/dʒiːˈɒdɨsi/), also named geodetics, is the scientific discipline that deals with the measurement and representation of the Earth.
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