The results of the adjustment consisted of corrections to initial station coordinates and coefficients of the gravitational field.The largest collection of data ever used for WGS purposes was assembled, processed and applied in the development of WGS 72.The latter observational method is more suitable for global mapping. Air Force had each developed a world system by using different approaches to the gravimetric datum orientation method.Therefore, a motivation, and a substantial problem in the WGS and similar work is to patch together datums that were not only made separately, for different regions, but to re-reference the elevations to an ellipsoid model rather than to the geoid. To determine their gravimetric orientation parameters, the Air Force used the mean of the differences between the gravimetric and astro-geodetic deflections and geoid heights (undulations) at specifically selected stations in the areas of the major datums.After an extensive effort extending over a period of approximately three years, the Department of Defense World Geodetic System 1972 was completed.Selected satellite, surface gravity and astrogeodetic data available through 1972 from both Do D and non-Do D sources were used in a Unified WGS Solution (a large scale least squares adjustment).This geoid defines the nominal sea level surface by means of a spherical harmonics series of degree 360 (which provides about 100 km horizontal resolution).(Mathematical and Physical Theory of Physical Geodesy).
The electronic satellite data consisted, in part, of Doppler data provided by the U. Navy and cooperating non-Do D satellite tracking stations established in support of the Navy's Navigational Satellite System (NNSS).Approximately 45 percent of the 410 mean free air gravity anomaly values were determined directly from observed gravity data.The astrogeodetic data in its basic form consists of deflection of the vertical components referred to the various national geodetic datums.In January 1966, a World Geodetic System Committee composed of representatives from the United States Army, Navy and Air Force, was charged with the responsibility of developing an improved WGS needed to satisfy mapping, charting and geodetic requirements.
Additional surface gravity observations, results from the extension of triangulation and trilateration networks, and large amounts of Doppler and optical satellite data had become available since the development of WGS 60.
Additional electronic satellite data was provided by the SECOR (Sequential Collation of Range) Equatorial Network completed by the U. Data from the Smithsonian Astrophysical Observatory was also used which included camera (Baker Nunn) and some laser ranging.