GPS·C
GPS·C (GPS Correction) was a Differential GPS data source for most of Canada maintained by the Canadian Active Control System, part of Natural Resources Canada. When used with an appropriate receiver, GPS·C improved real-time accuracy to about 1–2 meters, from a nominal 15 m accuracy. Real-time data was collected at fourteen permanent ground stations spread across Canada, and forwarded to the central station, "NRC1", in Ottawa for processing. Visiting the external webpage for this service on 2011-11-04, there is only a note saying that the service had been discontinued on 2011-04-01. There is a PDF link on that page to possible alternatives.