Researchers improving GPS accuracy in 3D
Researchers who are working to fix global positioning system (GPS) errors have devised software to take a more accurate measurement of altitude – particularly in mountainous areas.
The software is still under development, but in initial tests it enabled centimeter-scale GPS positioning – including altitude – as often as 97 percent of the time.
Researchers hope the software will help to improve the vertical accuracy of measurements in potentially hazardous regions at high altitudes, such as areas of soft, loose land that may be prone to landslides. They also claim that their software could be used to measure how quickly glaciers at high altitudes are melting.
The GPS is most commonly known for its ability to provide on-the-spot locations for drivers, but this application is just one of many possible uses, explained Dorota Grejner-Brzezinska, professor of civil and environmental engineering and geodetic science at Ohio State University. As the level of GPS precision increases, so do potential applications for scientific research.
While drivers are generally concerned with tracking their own location in two dimensions on the earth’s surface, the third dimension of altitude has always been available through GPS – just with lower accuracy than that of the horizontal coordinates.
Recently, Grejner-Brzezinska and her colleagues from the University of Warmia and Mazury in Poland have developed software that will allow GPS to relay locations to within a few centimeters’ accuracy, including altitude. While this high level of precision is not necessary for driving directions, it is necessary for recognizing small shifts in topsoil that may lead to dangerously destructive landslides.
She explained that a lot is going on behind the scenes during a typical use of GPS.
GPS satellites transmit information in the form of radio waves to the GPS receiver held by the user. At the same time, the signals must also travel to at least one other ground-based receiver to obtain a location reference, which allows the user’s receiver in turn to accurately calculate its own position in 3D. Before the satellite signals reach the receivers, they must travel through Earth’s atmosphere, which results in time delays that affect accuracy.
When the user’s receiver and the reference receiver reside at drastically different altitudes, however, each location experiences different amounts of time delay, which complicates matters even further. So, in mountainous regions where height differences can vary greatly over a short distance, acquiring the altitude of locations to within a few centimeters is difficult.