Land Surveyors' Equipment - Basic Use of a Total Station

by Ray Eddings

Have you ever seen a land surveying team using a camera-like devise on top of a tripod? Here's a quick explanation of that device, called a total station, and how it works.
A total station is a land-surveying tool used to accurately measure distances, architecture and geological land forms such as mountains. The device is extremely accurate, with some able to measure distances up to 0.1 millimeter or 1/1000 of a foot. Most surveyors don't need that much accuracy (which necessitates a higher cost out-of-pocket) and opt for a less expensive model accurate to 1 millimeter or 1/100 of a foot.
The total station itself looks a bit like a camera. You may have seen them mounted on a tripod -- they are often used at highway construction zones to measure the distance of an expansion, new on-ramp or other change to the traffic pattern. The standard unit includes a second piece attached to a pole.
This second piece is the reflector, and it is usually manned by a second surveyor. Matching the exact height of the total station relative to the reflector is extremely important to ensure accurate measurements, so often surveyors will do several trial runs before they note the points they're measuring. To aid in accuracy, the reflector point has a leveling bubble on its top, so that the person in charge of that end of the process can be sure the device is completely level.
Leveling the reflector is extremely important to ensure it matches the total station's height and gives an accurate distance reading that isn't skewed to the left or right, up or down.
Some newer total stations, including the Topcon total station, offer reflectorless measuring devices. These pinpoint an object using a scope in a view-finder chosen by the surveyor using the device. The Topcon total station then emits a modulated microwave or infrared signal that bounces off the target and back to the device, allowing it to measure distances out to about 1.5 miles (or 2 km).
Total stations are finding uses beyond land surveying. Police departments have begun using the devices to precisely measure and record elements of crime scenes. The data collected can offer a valuable record and even produce new information about the crime scene when processed through a computer.
About the Author
This article was written on behalf of http://southernphoto.com. For more information about land surveyors' equipment and land surveying visit their website.