Global Position Systems (GPS) are an indispensable tool for construction surveyors and land surveyors alike. GPS surveying may best be described as having 3 segments. The space segment, the control segment, and the user segment.
The space segment
The space segment consists of at least 24 satellites at an altitude of approximately 20,000 kilometer from the surface of the earth. The satellites are configured for optimal coverage so at least 4 satellites are visible at one time from any position on earth. The satellites contain extremely precise clocks that allow them to stay synchronized with other satellites and the ground control system. All satellite’s broadcast a unique PRN code (Pseudo Range Noise) that allows the user’s receiver on earth to make time based measurements to a satellite.
The control segment
The control segment consists of monitoring stations continuously tracking GPS at various locations throughout the world, and a master control station in the United States. The control stations transmit and receive data to and from the satellites. The control stations monitor performance, determine their orbits, model the atomic clock behaviour, and inject each satellite with their broadcast data.
The user segment
The user segment includes any equipment equipped with a GPS receiver capable of using GPS signals to determine positioning. In the basic mode the user’s receiver shifts a replica of the PRN code into alignment with the incoming signal from the satellites, and scaling their time shift by the speed of light to determine the distance to each satellite.
You may see GPS systems at work throughout Kelowna doing topographic surveys, construction layout surveys, legal surveying, and land surveying.
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