DATUM: A FORTRAN 77 computer program for datum shift and conversion of geographical coordinates between different cartographic systems

A computer program is described for the datum change of geographical coordinates over large areas. The transformation to geocentric coordinates and ordinary least-squares techniques are applied to a set of coordinates of points (minimum three) in the two reference systems. The parameters of rotation, translation, and scaling between the two ellipsoids are output, and are suitable to be tabulated to provide for further shifting of data in the same area. The results indicate that accuracies of a few meters can be achieved over an entire country by using a single set of parameters. Higher accuracies may be obtained by local conversion procedures. The program also is used for accurate direct and inverse geographical-to-metric coordinate conversion for nine most used mapping projections. Mathematical expressions and the FORTRAN 77 source listing are provided. © 1989.