Land surveying has been in practice almost since the beginning of civilization. Defining borders and knowing exactly how much land one owns is a basic human instinct, so the profession (some would call it the art) of land surveying developed to meet that need. Surveying is also used to triangulate the exact dimensions of a building or city before construction begins, so its importance can't be overstated.

In the beginning, land surveyors used lengths of chain, poles and complex mathematical equations to calculate the distance between two points in three dimensions. Over time, inventions have appeared that have made the land surveyor's job not only easier, but much more accurate. However, with the spread of digital, GPS and computer technology, sometimes surveyors can trade convenience for exact accuracy.

One of the earliest surveying tools was the theodolite. The first mention of the theodolite was found in the surveying text Pantometria, written in 1571 by Thomas Digges. A theodolite is an instrument that looks a bit like a small telescope mounted on a tripod.

The device can be used to calculate the distance from its location to a specified point -- usually a guy wearing a hard hat and holding a pole. The surveyor can look through the eyepiece of the theodolite, which contains mirrors and a small, etched piece of glass to measure distance, and gather the information he needs to triangulate the property. This device was the most widely used piece of surveying equipment for 200 years, until the invention of the total station in the 1970s.

The total stations of today use lasers to measure the distance from a known point to a prism in the field. Usually a total station will come equipped with a laser that is programmed to scan a small bar code or etched piece of glass inside the prism. Then, using trigonometry, the surveyor can calculate the coordinates on the X, Y and Z axes of the building, land site or construction site he's surveying. He then enters those coordinates into a data collecting device and downloads them onto his computer so that he can map the site in three dimensions.

Because boundaries are so important, and because the exact height, width and length of buildings can make the difference between a sound structure and one that will fall apart in 10 years, surveyors use technology to help them measure as accurately as possible. Digital levels measure the height of flat or sloping surfaces, and they can be used to measure the grade and ground profiles of a job site. They have the added advantage of being portable and lightweight, plus they can immediately send data straight back to the home office computer. High-quality digital levels will measure to a field of 30-40 centimeters.

Like digital levels, surveyors have adopted GPS technology to help them triangulate a point or position. GPS is still only accurate to about 3 or 4 meters, and surveyors take this into account when measuring a site. The GPS will usually be situated with a total station at a known point in space with exact coordinates -- latitude and longitude, for example. Then the surveyor will send a signal from the opposite point that the GPS will read and record. The total station can then give an approximate distance and measure height and width as well.

Surveyors use caution when relying upon GPS technology due to its large margin of error, but they applaud its invention as well. Mark Cheves, editor of Professional Surveyor magazine, says a job that used to require at least two people is now easy for one thanks to GPS. It's a good thing, too, Cheves says, because surveying is not the most popular profession. Making GPS even more vital is a shrinking number of experienced surveyors. More and more companies are requiring their new hires to have a four-year degree in a related field, and these graduates are highly coveted.