Computer software to calculate the systematic coordinate differences between two geodetic datums

The high degree of accuracy now found using GPS observation techniques has led to worldwide acceptance of the geocentric datums, specifically the WGS84 datum as the mainstay for referencing in the geodetic community. Nevertheless, local datums are non-geocentric and if we want to use GPS on their positions, some disagreement will result. This report presents PC-based software to transform coordinates between any two arbitrary datums. Transformations between NAD27 and NAD83 are used as examples expanded with the development of maps which illustrate shifts between those two datums in Latitude, Longitude, and Geoidal Height. It should be stressed that these transformations are based upon the standard seven parameters (3 shifts, 3 rotations, and scale change) and changes in the semimajor axis and the flattening including second partial differentials. This software does not take into account any random distortions that may be present in the datum coordinates.