What are NAD27 and ATS77?
Historically, New Brunswick has been in a continuous evolution with respect to its choice of datum. Since the late fifties, New Brunswick is up to the third datum selection. The two datum that were used and discarded are: • NAD27 (North American Datum of 1927) is based on the Clarke ellipsoid of 1866. This ellipsoid was adopted for the entire continent of North America as a basis for all geodetic computations. The datum is defined in terms of the values of the station Meade’s Ranch, State of Kansas. • ATS77 (Average Terrestrial System of 1977) is a geocentric ellipsoid of revolution. It was decided at the time that this mathematical figure most conveniently represents the size and shape of the earth for the Maritimes. ATS77 was in place for over 20 years. Similarly to NAD27, new technological tools like GPS (Global Positioning System) and GIS (Geographic Information Systems) came along and GPS data was not compatible with ATS77 thus forcing users to constantly perform transformation of
