The North American Datum of 1983 (NAD83) is the adopted reference coordinate system in both Canada (NAD83(CSRS)) and the United States (NAD83(NSRS)). It is a 3-dimensional representation of the NAD83 horizontal datum adopted in 1986. To comply with a resolution of the International Association of Geodesy (IAG), the North American plate fixed NAD83(CSRS) is rigorously related to the current International Terrestrial Reference Frame via a 6 parameter transformation (3 translations and three rotations). The ITRF scale was adopted for NAD83(CSRS) so that the two reference frames are very similar except for an approximate 2m difference in earth centre position.

Definition of NAD83(CSRS) and transformation to ITRF