The Michigan Dept. of Transportation is installing the last units of a 16-station network of corrected GPS control stations, whose data is upgraded every second and posted on the Internet for statewide survey control.

The system offers more corrections than the Continuously Operating Reference Stations (CORS), which the National Geodetic Survey, Washington, D.C., has been developing for eight years. That system will be paired with MDOT's. The Michigan system collects data every second, rather than every 30 seconds. The frequency is required for aerial photogrametric surveying, says Andy Semenchuk, CORS systems administrator for MDOT. He said the agency invested the $35,000 per station because the system allows MDOT to contract out surveying while maintaining quality control.

"It's a good sign," says Richard Snay, CORS manager with the National Geodetic Survey. "It's something started by the federal government and now states and private industry say, 'this is great, lets do it on the local level.' "