TRANSFORMATION OF COORDINATES BETWEEN 2 HORIZONTAL GEODETIC DATUMS

The following topics are discussed in this paper: the geocentric coord inate system and its different realizations used in geodetic practice; the definition of a horizontal geodetic datum (reference ellipsoid) a nd its positioning and orientation with respect to the geocentric coor dinate system; positions on a horizontal datum and errors inherent in the process of positioning; and distortions of geodetic networks refer red to a horizontal datum. The problem of determining transformation p arameters between a horizontal datum and the geocentric coordinate sys tem from known positions is then analysed. It is often found necessary to transform positions from one horizontal datum to another. These tr ansformations are normally accomplished through the geocentric coordin ate system and they include the transformation parameters of the two d atums as well as the representation of the respective network distorti ons. Problems encountered in putting these transformations together ar e pointed out.