SEAG data format

SEAG1 -- Free-air gravity anomaly, date, GMT, and latitude and longitude in radians. South latitude and west longitude are negative. Data were processed using the 1930 International Gravity formula. If data are merged with depth information (output of program MRGDS), data will include depth values and a simple Bouguer anomaly.
There are no SEAG1 data on this disk.

SEAG2 -- Free-air gravity anomaly, date, GMT, and latitude and longitude in radians. South latitude and west longitude are negative. Data were processed using the 1967 International Gravity formula.

Basic format with gravity processing and computed free-air gravity anomaly as output from program ATS3. If depth data were collected during the cruise, it would have been merged with the SEAG data generated by program ATS3 by program MRGDS to compute a simple Bouguer anomaly. If program MRGDS was run, the SEAG format would also include the depth values.

     COLS      FIELD NAME                         FORMAT
     ----      ---------------------------        ------
     1         record type indicator = 2            I1
     2-3       day                                  I2
     4-5       month                                I2
     6-7       year                                 I2
     8-11      time of day (GMT as HHMM)            I4
     8-9       hour of day                          I2
     10-11     minute of day                        I2
     12-14     time zone                            I3
     15-23     latitude (radians)                   F9.6
     24-32     longitude (radians)                  F9.6
     33-37     ship's velocity north (knots)        I5
     38-42     ship's velocity east (knots)         I5
     43-49     observed gravity (milligals)         F7.1
     50-54     free-air anomaly (milligals)         F5.1
     55-59     Bouguer anomaly (milligals)          F5.1
     60-64     current velocity north (knots)       I5
     65-69     current velocity east (knots)        I5
     70-74     corrected depth (meters)             I5
     75-77     depth correction (meters)            I5
     78-79     Matthews' table correction number    I2
     80-84     observed magnetic value (gammas)     I5
     85-89     Eotvos correction (milligals)        F5.1

OBSERVED GRAVITY: Total gravity field in milligals. The value is corrected for the Eotvos factor and may have been corrected for gravity-meter drift and for bias. Free-air and Bouguer anomalies have not been applied.
FREE-AIR ANOMALY: The calculated gravity anomaly, in milligals, at the data point. If data not available, the field equals 9999.
BOUGUER ANOMALY: If depth data are present, the Bouguer anomaly, in milligals, at the data point. If data not available, field equals 9999.
VELOCITY OF CURRENT NORTH & EAST: The difference between velocities calculated from the navigation fixes and those taken from the EM log.
MATTHEWS' TABLE: Matthews' table reference number 1-52.
OBSERVED MAGNETIC VALUE: If available, observed magnetic value for data point.
EOTVOS CORRECTION: The computed Eotvos correction that was applied to the raw gravity data.
Record Types:

1 = data processed using 1930 International gravity formula

2 = data processed using 1967 International gravity formula

9 = end of reel or data

SEAG example output of program ATS3:

          1         2         3         4         5         6         7         8         9
 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
 ------------------------------------------------------------------------------------------
 222 6761020  0  .550922-1.400567  616   769794496   13 9990  -78   55    0  0 00   0   91   
 222 6761025  0  .551052-1.400527  614   909794501   12 9990  -78   55    0  0 00   0   99   
 222 6761030  0  .551181-1.400483  608  1129794502    6 9990  -78   55    0  0 00   0  113   
 222 6761035  0  .551310-1.400436  611  1069794503    1 9990  -78   55    0  0 00   0  109   
 222 6761040  0  .551440-1.400392  616   989794504   -3 9990  -78   55    0  0 00   0  104   
 222 6761045  0  .551569-1.400349  621   879794508   -5 9990  -84   54    0  0 00   0   96   
 222 6761050  0  .551700-1.400311  621   779794511   -8 9990  -84   54    0  0 00   0   89   
 222 6761055  0  .551818-1.400245  525  2769794527    2 9990  -84   54    0  0 00   0  223   
 222 6761100  0  .551924-1.400144  515  3259794545   15 9990  -84   54    0  0 00   0  255   
 222 6761105  0  .552027-1.400037  511  3209794552   17 9990  -84   54    0  0 00   0  252

SEAG example output of program MRGDS:

          1         2         3         4         5         6         7         8         9
 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
 ------------------------------------------------------------------------------------------
 222 6761020  0  .550922-1.400567  616   769794496   13   38  -78   55   36  1 90   0   91
 222 6761025  0  .551052-1.400527  614   909794501   12   37  -78   55   36  1 90   0   99
 222 6761030  0  .551181-1.400483  608  1129794502    6   31  -78   55   36  0 90   0  113
 222 6761035  0  .551310-1.400436  611  1069794503    1   26  -78   55   36  0 90   0  109
 222 6761040  0  .551440-1.400392  616   989794504   -3   22  -78   55   36  0 90   0  104
 222 6761045  0  .551569-1.400349  621   879794508   -5   20  -84   54   36  0 90   0   96
 222 6761050  0  .551700-1.400311  621   779794511   -8   17  -84   54   36  1 90   0   89
 222 6761055  0  .551818-1.400245  525  2769794527    2   28  -84   54   37  1 90   0  223
 222 6761100  0  .551924-1.400144  515  3259794545   15   41  -84   54   38  2 90   0  255
 222 6761105  0  .552027-1.400037  511  3209794552   17   43  -84   54   37  2 90   0  252

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U.S. Department of the Interior, U.S. Geological Survey
URL: http://pubs.usgs.gov/of/1997/of97-512/htmldocs/formats/seag.htm
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Last modified: 09:37:54 Tue 18 Sep 2001
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