The Environmental Data Center in The University of Rhode Island's Department of Natural Resources Science has provided Global Positioning System (GPS) Base Station reference files to the public, free of charge, since 1991. GPS base station reference files allow advanced GPS users to achieve extremely high positional accuracies (even less than a centimeter!).
This service is sponsored by the University of Rhode Island's College of the Environment and Life Sciences, the URI Department of Natural Resources Science, the URI Environmental Data Center, the URI Geospatial Extension Program and the Rhode Island Renewable Resource Extension Act Program.
Up until July 2001, our system consisted of a Trimble Pathfinder Community Base Station receiver that was equipped to collect and serve single frequency, coarse acquisition (C/A) code GPS data. This GPS reference station was one of the first of its kind to operate in the Northeast United States, and supporting natural resource-based mapping applications requiring 2 to 5 meter accuracy.
Since then civilian use of GPS has grown exponentially, and demand for more precise positioning data has dramatically increased. The transportation, engineering, and environmental communities are employing high-order GPS field units capable of receiving the more precise carrier phase component of the GPS signal that may positional accuracies of less than 1 centimeter.
Through a grant from the University of Rhode Island Transportation Center, and in cooperation with Rhode Island Department of Transportation and Maine Technical Source, we upgraded in September 2001 to the high-order Trimble model 4700 reference station we still use today.
Our Continuously Operating Reference (CORS) station logs data from both L1 (C/A code) and L2 (carrier) frequencies at a 5 second interval, 24/7/365. The differential correction files are provided in several standard formats, and may be directly downloaded using software such as Trimble Pathfinder Office. This system is also an established node (URIL) in the national network of Cooperative CORS stations coordinated by the National Geodetic Survey.