01: Basic Knowledge
Global Positioning System (GPS)
GPS is a constellation of 24 satellites orbiting the Earth. These satellites have very accurate clocks and use radio signals to broadcast location information. Using satellites, a GPS receiver on the ground picks up the signals from the satellites to determine a location anywhere in the world. By adding sophisticated software, a base station and communications link, location can be accurately determined to the centimeter level.
Lasers are used in a range of applications to accurately determine level, grade, vertical alignment and distance. Spinning lasers emit a rotating 360-degree beam of light that is used as vertical, grade or horizontal reference, a difficult-to-establish yet critical datum for engineering and construction projects. Lasers are also used for measuring distance at high accuracy by determining phase shift or beam return time.
Optics are an integral part of an essential surveying instrument called a total station. This instrument enables the surveyor to compare locations in relation to one another. Optics allow survey and construction professionals to accurately pinpoint the exact feature to be measured while lasers measure the distance. In the past, making sure the optic lenses were positioned correctly within the instrument was an art. Today, sophisticated software helps calibrate these sensitive instruments, improving the accuracy and productivity of the surveyor.
Inertial technology senses changes in motion and is primarily used when GPS signals are obstructed. Starting with an initial location based on a landmark, inertial technology uses accelerometers and gyroscopes to determine the successive position based on movement. Inertial technology complements GPS and is currently used for aerial photogrammetry, vehicle tracking, high-end road construction and marine applications.