All conversions are based on the 7-parameter-Helmert transformation. 637 control monuments were used to calculate the 7 parameters and outliers were removed by means of statistical methods (ca. 10 % per transformation set). The ATS77 coordinates were than transformed to WGS84 by using the software package Transdat and to NAD83 coordinates by using the Nova Scotia Coordinate Transformation Web Application. To calculate the transform parameters, the 4 datasets for the control monuments were used. Because the elevations of the control monuments were not known in DEVCO coordinates as well as in ATS77 coordinates, it was assumed that the area covered by the coordinates is flat and no elevation correction is necessary.
Furthermore, the movement of the North American tectonic plate was not taken into account. WGS84 is based on the earth center of mass whereas NAD83 and ATS77 are based on the North American tectonic plate. Since the orignial definition of NAD83 and ATS77 the North American plate moved and consequently there might be a difference of 1 between WGS84 and the other coordinates.
The template must not be used to convert between ATS77, WGS84 and NAD83. Please use the Nova Scotia Coordinate Transformation Web Application.
© Christian Wolkersdorfer 2010