Evaluation of Gravity Data within the Department of Defense Gravity Library.
DEFENSE MAPPING AGENCY AEROSPACE CENTER ST LOUIS AFS MO
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The Department of Defense Gravity Library DODGL maintains an automated file of worldwide surface gravity observations. The gravity information in the database has been acquired from numerous sources including many scientific and government organizations, educational institutions, and private companies. To establish the quality of the gravity data in the database the data is subjected to review and evaluation and referenced to a common datum, the International Gravity Standardization Net of 1971 IGSN 71. The data evaluation process is designed to eliminate duplicate data and reduce errors to a minimum. Error sources include instrument and recording errors, horizontal or vertical positioning errors, data correction reduction errors, and uncertainties in base station connections and the IGSN 71. Relationships and fit between individual data sets are also a consideration. Based on results from the evaluation process, gravity data is deleted, modified, or adjusted to obtain the most error free data possible. An accuracy value is assigned to each gravity observation based upon all findings from the evaluation. When the evaluation of a data set has been completed, the database is updated to reflect the evaluated data. Due to ongoing gravity data acquisition, evaluation is a continuing process.
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