Not all RTK guidance systems can use DOT RTK corrections, but most can, Lagerstedt says. Deere systems currently cannot use DOT RTK corrections because the company uses a proprietary communications protocol, says Beuligmann of Deere. But the company is looking into adding that capability.

Leica plans to add, to its mojoRTK product line, the ability to access DOT RTK corrections without an external modem or cell phone. Current survey-grade RTK receivers from Leica, Trimble and others typically have this capability.

For information about RTK networks in Michigan, visit www.mdotcors.org and click on RTK User Agreement. In Minnesota, go to www.olmweb.dot.state.mn.us/CORS.GPS/cors.html. In Ohio, send an e-mail to aerial@dot.state.oh.us or call the survey operations manager at aaaaaaaaaaaa614/275-1359a. Information about the Iowa DOT network is available at www.dot.state.ia.us/rtn.

Additional regional public and private surveying-based RTK networks also have been built in the Midwest. Individual locations and operators of these RTK base stations are listed on a Web site of the National Geodetic Survey (NGS), an arm of the National Oceanic and Atmospheric Administration (www.ngs.noaa.gov/CORS/sort_sites).

NGS coordinates a cooperative network of these stations, which it calls Continuously Operating Reference Stations (CORS). Additional information can be found by searching for “CORS RTK” with a Web search engine.