97 Sep 22


To: Professionals of Surveying, Engineering, and GIS in Ohio, Kentucky, and Indiana


NCAD continues its second year providing a high-quality Continuously Operating Reference Station (CORS) for your use as part of the CORS Program administered by the National Geodetic Survey (www.ngs.noaa.gov/CORS/cors-data.html).

Global Positioning System (GPS) data collected by this CORS site, "erla," is available via the Internet from the National Geodetic Survey (NGS) or from NCAD. Beyond Erla, the nearest CORS sites are in Detroit, St. Louis, and Ashville, NC (det1, stl3, ashv). NCAD is the first non-governmental provider of a CORS.

GPS is the result of a multi-billion-dollar investment by the Department of Defense. The March, 1996, Presidential Decision Directive provides the guarantee of stable, expanding use by civilians of this utility primarily serving defense purposes.

At erla, GPS signals are received and processed by the Ashtech Choke-Ring antenna and Z12 dual-frequency receiver. The output data is recorded on the NCAD 6200 Server, operating with Microsoft Windows NT 4.0 Server, and then made available via FTP.

To use the CORS, you need only buy one receiver for "rover" activities such as navigation, mapping centerlines, and locating points. After you collect rover data in the field, you may download the corresponding reference data from the Erla CORS and post-process the rover data against the reference data. This will allow you to achieve highly accurate rover locations. How accurate? The rated capability of your rover determines the level of expected accuracy. For example, if you have an Ashtech Z-12 dual frequency receiver, you may expect accuracy of less than 1 cm. With the Ashtech Reliance Decimeter receiver, accuracies of 4 in. are obtainable.

NCAD is a private corporation committed to public service providing complete computer solutions for modeling, design, and information management of our developing world. We welcome your inquiry and look forward to assisting your implementation of this new utility.