Vertical Reference Systems

• Canadian Geodetic Vertical Datum of 2013 (CGVD2013)
• Canadian Geodetic Vertical Datum of 1928 (CGVD28)
• North American Vertical Datum of 1988 (NAVD88)

Canadian Geodetic Vertical Datum of 2013 (CGVD2013)

The Canadian Geodetic Vertical Datum of 2013 (CGVD2013) will be officially release in November 2013 and will replace the Canadian Geodetic Vertical Datum of 1928 (CGVD28). CGVD2013 is a gravimetric datum defined by the equipotential surface W0 = 62,636,856.0 m2s-2, representing the average potential of coastal mean sea level at tide gauges across North America. The definition and geopotential value come from an agreement between Canada and USA.  Heights in terms of CGVD2013 are in the orthometric height system.

The Canadian Gravimetric Geoid Model of 2013 (CGG2013) will be the first realization of the vertical datum.  CGG2013 will be available in NAD83(CSRS) and ITRF2005 for the ellipsoid of GRS80 in the binary format byn. Software GPS-H, which converts ellipsoidal heights to orthometric heights using a geoid model, will allow the transformation of CGG2013 to any other ITRF realizations and reference ellipsoids. CGVD2013 is consistent with Global Navigation Satellite Systems (e.g., GPS and GLONASS).

The levelling networks (mainland, Prince Edward Island, Newfoundland, Vancouver and other islands) will be readjusted in conformity with CGVD2013 by constraining the levelling measurements to stations with precise ellipsoidal heights in NAD83(CSRS).  The CGVD2013 heights at the benchmarks will not be considered official because they will be coming from an adjustment of legacy data.  NRCan is not in a position to be able to confirm stability of the benchmarks. The official height at a benchmark will be determined by GNSS technique and the CGG2013 geoid model.

Canadian Geodetic Vertical Datum of 1928 (CGVD28)

The Canadian Geodetic Vertical Datum of 1928 (CGVD28) is the vertical datum for Canada.   It was officially adopted by an Order in Council in 1935.  CGVD28 is a tidal datum defined by the mean water level at five tide gauges: Yarmouth and Halifax on the Atlantic Ocean, Pointe-au-Père on the St-Lawrence River, and Vancouver and Prince-Rupert on the Pacific Ocean.  In addition, the definition includes an elevation at a benchmark in Rouses Point, NY (next to Lake Champlain) accepted as fixed by the US and Canada in 1925.  The datum is propagated in land using geodetic levelling measurements.  The vertical datum is accessible through benchmarks anchored to the ground and stable structures.  The heights in terms of CGVD28 are in normal-orthometric system. 

North American Vertical Datum of 1988 (NAVD 88)

The North American Vertical Datum of 1988 (NAVD 88) is the vertical datum for the USA. It was affirmed as the official vertical datum in the National Spatial Reference System (NSRS) for the Conterminous United States and Alaska in 1993.  NAVD88 is a tidal datum defined by the mean water level at the tide gauge in Rimouski, Québec.  The datum is propagated in land using geodetic levelling measurements.  The vertical datum is accessible through benchmarks anchored to the ground and stable structures.  The heights in terms of NAVD 88 are in Helmert orthometric.

Canada did not adopt the North American Vertical Datum of 1988; however, NAVD88 heights are available on a subset of the Canadian levelling network.