Editing World Geodetic System (section)

==={{anchor|WGS66}}WGS&nbsp;66===
Improvements to the global system included the Astrogeoid of [[Irene Fischer]] and the astronautic Mercury datum. In January 1966, a World Geodetic System Committee composed of representatives from the United States Army, Navy and Air Force was charged with developing an improved WGS, needed to satisfy [[map]]ping, charting and geodetic requirements. Additional surface [[gravity]] observations, results from the extension of [[triangulation]] and [[trilateration]] networks, and large amounts of [[Doppler radar|Doppler]] and [[optical]] satellite data had become available since the development of WGS 60. Using the additional data and improved techniques, WGS 66 was produced which served DoD needs for about five years after its implementation in 1967. The defining parameters of the WGS 66 Ellipsoid were the flattening ({{frac|1|298.25}} determined from satellite data) and the semimajor axis ({{val|6378145|u=meters}} determined from a combination of Doppler satellite and astro-geodetic data). A worldwide 5° × 5° mean free air [[gravity anomaly]] field provided the basic data for producing the WGS 66 gravimetric geoid. Also, a geoid referenced to the WGS 66 Ellipsoid was derived from available astrogeodetic data to provide a detailed representation of limited land areas.