This data is then distributed over the Internet for download and archived for future use. Working 24 hours a day, seven days a week, CORS continuously receive GPS radio signals and integrate their positional data into the National Spatial Reference System. The NCN is a network of a couple thousand stationary, permanently operating GPS receivers operated by NGS and its partners, which are located throughout the United States and its territories. To provide measurements at this level of accuracy, NGS developed the NOAA Continuously Operating Reference Stations (CORS) Network (NCN). But there are many scientific, military, and engineering activities that require much higher levels of positioning accuracy - often to within a few centimeters or less! This level of accuracy may be adequate for a hiker in the woods or someone driving a car. Considering that the Earth is almost 25,000 miles in circumference, the difference of a few meters may not seem important. As advanced as GPS technology is, most commercially available GPS receivers are only accurate within several meters. In a field of study that is thousands of years old, GPS represents a quantum leap in geodesy.
