Index of Gravity Surveys - Geoscience Australia

EXPLANATORY NOTESThe following notes describe each of the fields listed in the Index.Access Code:Indicates whether data from the survey are open file or confidential.Contractor:Country:‣ A – These data are restricted to users inside GA. Data cannotbe released to the public without proper authorisation from theowner.‣ C – Confidential data. The use of these data is restricted tousers with approved access.‣ D – Deactivated data. Usually because data are incompatiblewith adjoining data sets.‣ O – Open file data. There are no restrictions on these data.‣ R – Restricted data which cannot be released to the publicwithout the owner’s approval.The organisation which acquired the survey data.The country in which the survey was located.Geodetic Datum:‣ ATA – Antarctica.‣ AUS – Australia.‣ NZL – New Zealand.‣ PNG – Papua New Guinea.The mathematical surface on which coordinates used in the survey arebased. For example, older GA surveys use the AGD66 datum whichis based upon the regional Australian National Spheroid (ANS). Since1990s, most surveys recorded horizontal coordinates with respect tothe Geocentric Datum of Australia (GDA94). The GDA94 datum hasbeen adopted in Australia since the beginning of 2000.Gravity Acc:Gravity Datum:‣ AGD66 – Australian Geodetic Datum 1966.‣ AGD84 – Australian Geodetic Datum 1984.‣ ANG – Australian National Grid (used prior to 1966).‣ GDA94 – Geocentric Datum of Australia 1994.‣ WGS84 – World Geodetic System 1984.The accuracy or error, expressed in units of micrometres per secondsquared in the observed gravity readings.The gravity datum to which the original survey has been tied.Grd Elev Acc:Grd Elev Datum:‣ I – International Gravity Standardisation Net 1971 (IGSN71)Datum using the Geodetic Reference System 1967 (GRS67)formula.‣ N – Isogal84 based on IGSN71 using the GRS67 formula.‣ O – Isogal65 Datum using the 1930 formula.‣ P – Potsdam Datum using the 1930 normal gravity formula.The accuracy or error, expressed in metres, in determining the stationground elevation.The height datum to which ground elevations are referenced.27 January 2006 © Copyright Geoscience Australia 2006 ix