Development of Surveying Technology BY yan93 Surveying is believed to be the third oldest profession in the world. To a surveyors, the link chain symbolizes a rugged era, in terms of evolution of surveying technology and equipments. The chain was a precision part of a surveyor’s equipment for years. Then the Renaissance in education and scientific knowledge provided the necessary intellectual foundation for the development of modern surveying. With the advent of the electronic distance meter, GPS, GIS, and computer-controlled Land Surveying, the profession of surveyors has turned from a labor-intensive type into a more sedate one.
A brief chronology of surveying instruments provided here, traces the history of surveying: Around 1400 B. C. , the Egyptians first used the predecessors of modern surveying instruments to accurately divide land into plots for the purpose of taxation and to engineer many feats, from canals to pyramids. An ancient Egyptian survey crew used measuring ropes, plumb bobs, sighting instruments, and leveling instruments. The ancient Egyptian measuring rope was stretched taut between stakes and then rubbed with a mixture of beeswax and resin.
Some of the ropes depicted in hieroglyph were graduated by knots tied at intervals. Image courtesy: www. surveyhistory. org/images/egyptian. JPG Diopter Around 120 B. C. , Greeks developed the science of geometry and were using it for precise land division. Greeks developed the first piece of surveying equipment (Diopter). In a work entitled Diopter, Hero of Alexandria, describes it as a portable instrument, an application of the cogwheel, screw, and water level, for taking terrestrial and astronomical measurements.
Because of some similarities, Hero’s diopter is usually recognized as the ancestor of the modern theodolite. Image courtesy: http://vitruvio. imss. fl. it/foto/sim/simapprart/ imapprart-201203_1 50. Jpg Magnetic Compass during the Qin dynasty (221-206 B. C. ) Lodestones (a mineral composed of an iron oxide which aligns itself in a north-south direction) turned out to be better at pointing out real directions, leading to the first compasses. They designed the compass on a square slab which had markings for the cardinal points and the constellations.
The pointing needle was a lodestone spoon-shaped device, with a handle that would always point south. Magnetized needles used as direction pointers instead of the spoon-shaped lodestones appeared in the 8th century AD, gain in China, and between 850 and 1050 they seem to have become common as navigational devices on ships. Image courtesy: www. rockingham. kl 2. va. us/JWES/China/chinacompass. gif Sextant Two men independently rediscovered the sextant around 1730: John Hadley (1682-1744), an English mathematician, and Thomas Godfrey (1704-1749), an American inventor.
A sextant is a navigation instrument used for measuring angles, primarily altitudes of celestial bodies. Originally, the sextant had an arc of 600, or 1/6 of a circle, from which the instrument derived its name. Because of the double- eflecting principle used, such an instrument could measure angles as large as 1200. The image shown is of an early sextant by John Bird which was invented in 1759. The frame is mahogany with an ivory scale. It is so large and heavy that it needed a support that fitted into a socket on the observers belt.
Image Courtesy:www. mat. uc. pt/??”helios/Mestre/NovembOO/H61 _fl 1 . JPG Theodolite The Jesse Ramsden theodolite is a large theodolite which was specially constructed for use in the first Ordnance Survey of Southern Britain in 1787. In 1791 Ramsden’s theodolite with a 3 ft. ircle reading to 1″ built was used for the angle observations and despite its weight of about 300 lbs. good progress was obtained in the triangulation. It is certainly among the 4 or 5 greatest technological advances ever in geodetic surveying.
In the field of general surveying however, the invention by the French of the repeating theodolite about 1790 is of equal importance for it is the basis for the instrument most surveyors have employed. Image courtesy: www. sciencemuseum. org. uk/images/1016/10279344. aspx Alidade The term alidade can refer to the sighting mechanism of any instrument used for sed with a plane table for topographical work??”that is, for mapping the surface features of the earth. Early alidades were simple bars with open sights at either end.
Telescopic alidades came into use in Europe in the early 19th Century, and were soon introduced to American practice. In 1865 the United States Coast Survey stated that the plane table with telescopic alidade was the “principal instrument for mapping the topographical features of the country,” and noted that it was “universally recognized as the most efficient and accurate means for that purpose. ” The image showm is of the High-post alidade, made by Gurley in 1914. Courtesy: www. orbitals. com/pic/survey/big/s026-041 Jpg Dumpy Level William Gravatt introduced the dumpy level in 1830.
The Dumpy level was a simple device that was nothing more then a small telescope with a bubble level attached to it. Its telescope is short and fat (hence the name), and fixed in its supports. The level was considered the standard, uptil around the 1830’s when the transit level was invented. Image courtesy: http://celebrating200years. noaa. gov/foundations/leveling/ imagel . html Transit The transit was the most important surveying instrument in the United States in the 19th century. But William J. Young, who invented the form in 1831, did not see it as something new, but simply a modification of his new railroad compass.
In an advertisement in the American Railroad Journal for March 23, 1833, Young described the transit as “an Improved Compass, with a Telescope attached, by which angles can be taken with or without the use of the needle, with perfect accuracy. ” By 1837, the new instrument was known as a transit. Image courtesy: http://americanhistory. si. edu/collections/surveying/enlarge. cfm? recordnumber=746054 Solar Compass In 1835 The solar compass was invented by William Austin Burt of Michigan. The True North”.
By making observations on the sun or other stars, the latitude of the location can first be determined and then “True North” can be determined. The solar compass also has the ability to measure horizontal angles much like a transit. Image courtesy:www. surveyhistory. org/images/solar. JPG Gunter’s Chain 1839 onwards land surveyors in the colony of Queensland used the Gunter’s Chain to measure the boundaries of town allotments and country selections (farms). Originally manufactured in England. One hundred LINKS in length (approximately 20 metres. ) used for measurement of land boundaries up to 1880’s. Image courtesy: www. eom. unimelb. edu. au/collection/item_details_l . html Steel Measuring Band Steel measuring band was developed in Australia to suit local conditions in late 19th century. Common lengths were 300 feet, 500 links and 100 metres. Usually graduated with a brass tag at each unit of 10 and a copper tag at each 100. The last 10 at each end was graduated in smaller units. Image courtesy: www. geom. unimelb. edu. au/collection/item_details_2. html Geodimeter In 1953, the Geodimeter, the first EDM using visible light (laser) beams or radio frequencies to measure distances, was produced in Sweden by Erik Bergstrand.
This instrument, named the Geodimeter, would reduce the time required to measure base lines from weeks to hours, without any reduction in the accuracy of the line. Furthermore, it permitted the measurement of regular length triangulation lines, doing away with the costly and accuracy lessening expansion nets. Image Courtesy of Sokkia Total Station Beginning in the 1970’s, a virtual plethora of short range EDMI, modern transits and By the late 1980’s, most surveyors were equipped with at least one of the new instruments. There was one problem, EDMI require periodic accuracy evaluations nd verification of the instrument constant.
Image courtesy: www. geology. ucdavis. edu/??”gold/images/cowgill_ts. ]pg GPS The Global Positioning System (GPS) (officially named as NAVSTAR GPS) is the only fully functional Global Navigation Satellite System (GNSS). Using a constellation of 24 medium Earth orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its location, speed/direction, and time. In 1972, the US Air Force Central Inertial Guidance Test Facility (Holloman AFB) conducted developmental fight tests of two prototype GPS receivers over White Sands Missile Range, using ground-based pseudo-satellites.
By January 17, 1994 a complete constellation of 24 satellites was in orbit. The most recent launch was on 17 November 2006. The oldest GPS satellite still in operation was launched in August 1991. 3-D Laser Scanner The 3-D laser scanner is an active scanner that uses laser light to probe the subject. At the heart of this type of scanner is a laser range finder. The laser range finder finds the distance of a surface by timing the round-trip time of a pulse of light. A laser is used to emit a pulse of light and the amount of time before the reflected light s seen by a detector is timed.
The National Research Council of Canada was among the first institutes to develop the triangulation based laser scanning technology in 1978. The laser range finder only detects the distance of one point in its direction of view. Thus, the scanner scans its entire field of view one point at a time by changing the range finder’s direction of view to scan different points. Leica geosystems introduced the first handheld laser distance meter in 1993 Image courtesy: www. leica-geosystems. com/corporate/en/ndef/lgs_5574. htm september/58_3. htm
