Knowledge Bank

In June 1986 a 1° x 1° mean free-air anomaly data file containing 48955 anomalies was completed. In August 1986 a 30' x 30' mean free-air anomaly file was defined containing 31787 values. For the past three years data has been collected to upgrade these mean anomaly files. The primary emphasis was the collection of data to be used for the estimation of 30' mean anomalies in land areas. The emphasis on land areas was due to the anticipated use of 30' anomalies derived from satellite altimeter data in the ocean areas. There were 10 data sources in the August 1986 file. Twenty-eight sources were added based on the collection of both point and mean anomalies from a number of individuals and organizations. A preliminary 30' file was constructed from the 38 data sources. This file was used to calculate 1° x 1° mean anomalies. This 1° x 1° file was merged with a 1° x 1° file which was a merger of the June 1986 file plus a 1° x 1° file made available by DMA Aerospace Center. Certain bad 30' anomalies were identified and deleted from the preliminary 30' file leading to the final 30' file (the July 1989 30' file) with 66990 anomalies and their accuracy. These anomalies were used to again compute 1° x 1° anomalies which were merged with the previous June 86 DMAAC data file. The final 1° x 1° mean anomaly file (the July 89 1° x 1° data base) contained 50793 anomalies and their accuracy. The anomaly data files were significantly improved over the prior data sets in the following geographic regions: Africa, Scandinavia, Canada, United States, Mexico, Central and South America. Substantial land areas remain where there is little or no available data.