CGS provides access to NAD83(CSRS) coordinates for about 150 stations of the Canadian Base Network (CBN) and about 3,000 vertical control benchmarks observed with GPS. In addition, elevations in CGVD28/2013 and horizontal coordinates in NAD83(Original) are made available for over 100,000 points of the conventional first order networks. An interactive map of the passive control networks is available through the NRCan Passive Control web application.
Canadian Base Network (CBN)
CBN monuments were established in the 1990’s to complement the CACS and anchor the densification of provincial high-precision networks. The CBN stations have stable pillars with forced-centering plates intended for multi-epoch high-accuracy GNSS positioning. On average, the pillars are at 200 km spacing in most of southern Canada, 500 km in the northern part of the larger provinces, and 1000 km in the Territories. All stations of the CBN have now been observed at least 4 times, at intervals of 5-7 years, to estimate coordinate changes at the sites and derive a national velocity grid. This velocity grid has now become an essential tool to convert geodetic coordinates between adopted epochs of NAD83(CSRS) and account for the systematic effect of crustal motion within the Canadian portion of the North-American plate.
GPS on Benchmarks (High-precision SuperNet)
This extended network consists of approximately 3,000 3D stations that were observed with GPS and tied to NAD83(CSRS) at epochs 1997 or 2002. The federal HPN network (Supernet) was observed to verify the accuracy of geoid models and help to produce the HTv2* height transformation. In this High Precision Network, various older monuments originally tied using traditional surveying methods were re-observed with GPS.
*Height transformation version 2.0 (HTv2) is a hybrid geoid model based on the earlier geoid model of CGG2000 that has been distorted to fit with CGVD28 benchmarks published elevations.