U.S. researchers working on the accuracy of GPS location say they have set their sights on the third dimension with software to improve altitude measurements.While most people are generally concerned with pinpointing their own location in two dimensions on Earth\'s surface, the third dimension of altitude has always been available through GPS -- but the accuracy has always been lower than that of the horizontal coordinates, researchers at Ohio State University said.They\'re working on software that in initial tests provided vertical accuracy to centimeter-scales -- a matter of inches, a university release said Wednesday. As the level of GPS precision increases, the researchers say, so do potential applications of the technology for scientific research, said Dorota Grejner-Brzezinska, OSU professor of civil and environmental engineering.For example, extremely accurate measurements in the vertical dimension could identify changes in hazardous regions at high altitudes, recognizing small shifts in soft, loose land that may be prone to landslides, researchers said.The software could be used to measure how quickly glaciers at high altitudes are melting, they said.