Exporting - MGD77 (from Raw Data Manager)

Export to single file

This is an option to combine the MGD77 output of multiple files (selected in the Raw Data Manager) into a single file.
Typically MGD77 are separated line by line. However, if all the data for a line is not stored in one DB/RES file combination, either because DB files have been split (setting in Controller - Settings - Session Setup - Storage) or the line was shot in multiple pieces, there may be a need to combine the output in order to derive a single output file from multiple input files.

Selecting this option activates the Browse button which opens the Project Export folder. Give the combined MGD77 file a name.

Clicking on the Explore button also opens the Project Export folder for inspection only.

Export data from entire results file

All data is stored in the results file, from the first recorded fix to the last. Exactly what is stored depends on other settings. See below.

Export data partially, from fix number

By default the first and last fix recorded in the *RES file are displayed. This option allows the fix range to be modified, which might be the case when fixes on the line run-in and run-out are not required in the MGD77 file.

Export data for fix events only

*.DB files contain all the raw data recorded and *.RES files contain all positions calculated. This option restricts data output to the subset of positions computed at the time of each fix.

Export all inter-event data

*.DB files contain all the raw data recorded and *.RES files contain all positions calculated. This option exports all the positions calculated, the frequency of which is based on the triggering system used for the computation cycle.

Input Results File

Lists the *.RES file associated with the *.DB file selected in the Raw Data Manager.
If multiple *.DB files are selected, only one will be displayed.

The data record presents underway marine geophysical data in a correlative manner.  Geophysical data (bathymetry, magnetics, and gravity) and seismic identification (shot-point identification) are presented with a corresponding time and position. 

RECORD TYPE - Set to "4"
SURVEY IDENTIFIER
FORMAT ACRONYM - Set to"MGD77"
DATA CENTER FILE NUMBER
PARAMETERS SURVEYED CODE
FILE CREATION DATE (YYYYMMDD)
SOURCE INSTITUTION
SEQUENCE NUMBER - Set to "01"

COUNTRY
PLATFORM NAME
PLATFORM TYPE CODE
PLATFORM TYPE (e.g., "SHIP","PLANE", "SUB", etc.)
CHIEF SCIENTIST(S)
SEQUENCE NUMBER - Set to "02"

PROJECT (e.g., "SURVOPS 6-69", "INDOPAC, Leg3")
FUNDING (i.e. agency or institution)
SEQUENCE NUMBER - Set to "03"

SURVEY DEPARTURE DATE (YYMMDD)
PORT OF DEPARTURE (i.e. city, country)
SURVEY ARRIVAL DATE (YYMMDD)
PORT OF ARRIVAL (i.e. city, country)
SEQUENCE NUMBER - Set to "04"

NAVIGATION INSTRUMENTATION (e.g. "SAT/LORAN A/SEXTANT")
GEODETIC DATUM/POSITION DETERMINATION METHOD (e.g. "WGS84/PRIM - SATELLITE, SEC-LORAN A")
SEQUENCE NUMBER - Set to "05"

BATHYMETRY INSTRUMENTATION
ADDITIONAL FORMS OF BATHYMETRIC DATA (e.g., "MICROFILM","ANALOG RECORDS")
SEQUENCE NUMBER - Set to "06"

MAGNETICS INSTRUMENTATION (e.g., "PROTON PRECESSION MAG-GEOMETRICS G-801")
ADDITIONAL FORMS OF MAGNETICS DATA (e.g., "PUNCH TAPE","ANALOG RECORDS")
SEQUENCE NUMBER - Set to "07"

GRAVITY INSTRUMENTATION (e.g., "L and R S-26")
ADDITIONAL FORMS OF GRAVITY DATA (e.g., "MICROFILM", "ANALOG RECORDS")
SEQUENCE NUMBER - Set to "08"

SEISMIC INSTRUMENTATION
FORMATS OF SEISMIC DATA (e.g., "DIGITAL", "MICROFILM", "NEGATIVES", etc.)
SEQUENCE NUMBER - Set to "09"

FORMAT TYPE
FORMAT DESCRIPTION
SEQUENCE NUMBER - Set to "10"

FORMAT DESCRIPTION Continued
TOPMOST LATITUDE OF SURVEY
BOTTOMMOST LATITUDE
RIGHTMOST LONGITUDE
SEQUENCE NUMBER - Set to "11"

GENERAL DIGITIZING RATE OF BATHYMETRY
GENERAL SAMPLING RATE OF BATHYMETRY
ASSUMED SOUND VELOCITY
BATHYMETRIC DATUM CODE
INTERPOLATION SCHEME
SEQUENCE NUMBER - Set to "12"

GENERAL DIGITIZING RATE OF MAGNETICS
MAGNETIC SENSOR TOW DISTANCE
SENSOR DEPTH
HORIZONTAL SENSOR SEPARATION
REFERENCE FIELD CODE
REFERENCE FIELD (e.g., "IGRF-85")
METHOD OF APPLYING RESIDUAL FIELD
SEQUENCE NUMBER - Set to "13"

GENERAL DIGITIZING RATE OF GRAVITY
GENERAL SAMPLING RATE OF GRAVITY
THEORETICAL GRAVITY FORMULA CODE
THEORETICAL GRAVITY FORMULA (e.g., "INTERNATIONAL '30", "IAG SYSTEM (1967)", etc.)
REFERENCE SYSTEM CODE
REFERENCE SYSTEM (e.g., "POTSDAM SYSTEM", "SYSTEM IGSN 71", etc.)
CORRECTIONS APPLIED (e.g., "+0.075 MGAL PER DAY")
SEQUENCE NUMBER - Set to "14"

DEPARTURE BASE STATION GRAVITY
DEPARTURE BASE STATION DESCRIPTION
ARRIVAL BASE STATION GRAVITY
ARRIVAL BASE STATION DESCRIPTION
SEQUENCE NUMBER - Set to "15"

NUMBER OF 10-DEGREE IDENTIFIERS **
10-DEGREE IDENTIFIERS
SEQUENCE NUMBER - Set to "16"

10-DEGREE IDENTIFIERS (Continued)
SEQUENCE NUMBER - Set to "17"

ADDITIONAL DOCUMENTATION
SEQUENCE NUMBER ("18" thru "24")

Survey Identifier

Defaults to the identifier defined in DbSetup. If nothing was entered in DbSetup, enter up to 8 characters.
Identical to the identifier in the header record Sequence #1.

Reference Computation

Choose the computation to be used for output of positions. Computation listed are those defined under Controller - Settings - Computation Settings.

Reference Position

Choose which node to use as the reference position for output of positions. Nodes listed are those defined in DbSetup.

Bathymetric Correction Code

This code details the procedure use for determining the sound velocity correction to depth. Various formulas based on theoretical and empirical methods have been proposed since the 1920s. Please refer to A Brief History of Sound Velocity Corrections.
Choose which code was used for depth correction:

Unspecified - there is no knowledge of what depth correction method was used for the survey.

Matthews' Zones, with zone - based on velocities obtained theoretically, D. J. Matthews divided the world’s oceans into discrete areas linking regions with common sound velocity profiles, and constructed a table for each area with the depth corrections to be applied at various depths down the water column. These tables were prepared for the UK Hydrographic Office by Matthews in 1927 and a second edition, extensively revised by the same author, appeared in 1939. The second edition became known as Matthews’ Tables and at the 5^th International Hydrographic Conference in 1947, the tables were adopted as the standard for use in all hydrographic offices.

Matthews' Zones, no zone - Matthews’ corrections were used to correct depths but the zone number is unspecified in the data record.

S. Kuwahara Formula - In 1939 Kuwahara also produced correction tables based on velocities obtained theoretically.

Wilson Formula - Formula based on laboratory measurements proposed by Wilson 1960.

Del Grosso Formula - Formula based on laboratory measurements proposed by Del Grosso 1973.

Carter's Tables - In 1980 a third edition of Echo-Sounding Tables was published by the UK Hydrographic Office to replace Matthews’ Tables. The tables were extensively revised to incorporate the large number of temperature and salinity measurements obtained since 1939. They also used an improved formula for the dependence of sound velocity on temperature and salinity. Computations for the revised tables were carried out by D. J. T. Carter of the Institute of Oceanograhic Sciences, Wormley, UK, using oceanographic station data provided by the U.S. National Oceanographic Data Center, Washington DC. The revised tables, together with a detailed description of their preparation, may be found in Echo-Sounding Correction Tables (1980 3^rd Edition), Publication NP139 of the UK Hydrographic Office.

In 1982, the 15^th International Hydrographic Conference at Monaco decided to adopt the third edition in place of Matthews’ Tables. These tables are applicable for use throughout the world in depths greater than 200 meters. The boundaries of each of the 85 areas lie along exact degrees of latitude and longitude. The tables are expressed in meters and assume an echo-sounder velocity of 1500 m s^-1.The tables were computerized by Carter and offer standard velocity-depth corrections for 85 different regions covering the globe. The database consists of algorithms for determining correction zones by latitude-longitude, and interpolation tables for each zone. A digital version of the Echo-Sounding Correction Tables (3rd. Edition) is available to download https://www.bodc.ac.uk/products/software_products/carters_tables/.

Other - Any other method as described in header sections.

Zone

Field only shown when 'Matthews' Zones, with zone' is selected.
Enter zone number 1-55.
Note: the following zone numbers are entered automatically based on selection of Correction Code other than "Matthews' Zones, with zone":
99 = unspecified.
59 = Matthews’ corrections used but the zones is unspecified in the data record.
60 = S. Kuwahara formula for temperature and salinity (T-S).
61 = Wilson formula for T-S.
62 = Del Grosso formula for T-S.
63 = Carter’s tables.
88 = Other, described in header sections.

Bathymetry Td. Computation

Choose the computation to be used for output of echosounder transducer positions. Computation listed are those defined under Controller - Settings - Computation Settings.

Bathymetry Td. Position

Choose which node to use as the transducer for output of positions. Nodes listed are those defined in DbSetup.

Bathymetry Observation

Choose the depth observation to output. Observations listed are those defined in DbSetup.

Magnetometer Computation

Choose the computation to be used for output of the magnetometer positions. Computation listed are those defined under Controller - Settings - Computation Settings.

Magnetometer Position

Choose which node to use as the magnetometer for output of positions. Nodes listed are those defined in DbSetup.

Magnetometer Observation

Choose the magnetometer observation to output. Observations listed are those defined in DbSetup.

Second Magnetometer

Select another magnetometer if employed during the survey. Observations listed are those defined in DbSetup.

1

Survey identifier:

Defaults to the identifier defined in DbSetup. If nothing was entered in DbSetup, or a different identifier is wanted, enter up to 8 characters.
Identical to the identifier in the Data Record.

Format:

Read from the Format Name entered in DbSetup - General - Media & Format Specification. Typically this would be set to"MGD77".
If nothing was entered in DbSetup, or a different format name is wanted, enter up to 8 characters.

Data Center File No.:

Read from the Project Name entered in DbSetup - General - Project Information.
If nothing was entered in DbSetup, or a different number is wanted, enter up to 5 characters.

Source Institution:

Read from the Project Name entered in DbSetup - General - Company Information.
If nothing was entered in DbSetup, or a different name is wanted, enter up to 39 characters.

2

Country:

Enter name of country (up to 18 characters).

Platform Name:

Name of towing vessel copied from template database. Changeable (up to 21 characters).

Platform Type Code:

Select one of the following from the drop down list:
0 - Unspecified
1 - Surface ship
2 - Submersible ship
3 - Aircraft
4 - Buoy
5 - Mobile land
6 - Fixed land
7 - Deep tow
8 - Anchored seafloor instrument
9 - Other, specify

Platform Type:

Enter name (e.g., "SHIP","PLANE", "SUB", etc.). Up to 6 characters.

Chief Scientist(s):

Enter name (up to 32 characters).

3

Project:

Read from the Survey Type/Location entered in DbSetup - General - Project Information.
If nothing was entered in DbSetup, or a different name is wanted, enter up to 58 characters.

Funding:

Enter name of funding source (up to 20 characters).

4

Departure Date:

Read from the Start Date entered in DbSetup - General - Project Information.
If nothing was entered in DbSetup, or a different date is wanted, select the date from the drop down calendar.

Port of Departure:

Enter up to 32 characters.

Arrival date:

Read from the End Date entered in DbSetup - General - Project Information.
If nothing was entered in DbSetup, or a different date is wanted, select the date from the drop down calendar.

Port of Arrival:

Enter up to 30 characters.

5

Navigation Instrument:

Entry is copied from the Reference Computation field in the Data Record, as selected on the previous page of the wizard.
Changeable (up to 40 characters).

Geodetic Datum:

Defaults to name of Survey Datum defined in the DbSetup template database. Changeable (up to 38 characters).

6

Bathymetry Instrument:

Entry is copied from the Bathy Observation field in the Data Record, as selected on the previous page of the wizard.
Changeable (up to 40 characters). Include information such as frequency, beam width, and sweep speed of recorder.

Add. Forms of Bathy Data:

Enter any additional forms in which the bathy data is stored (e.g., "Microfilm","Analog Records").
Up to 38 characters.

7

Magnetics Instrument:

Entry is copied from the Magnetometer Observation field in the Data Record, as selected on the previous page of the wizard.
Changeable (up to 40 characters). Include any useful information such as sample rate, cycle time in seconds per reading, Bandwidth or bandpass, Resolution, Absolute error, Drift, Noise, Sensitivity, Heading error, etc..

Add. Forms of Magnetics Data:

Enter any additional forms in which the Magnetics data is stored (e.g. "Analog Records").
Up to 38 characters.

12

Bathy Digitizing Rate (second):

Output rate of digital data in seconds as read from Event Interval entered in Controller - Settings - Session Setup - Fixing when Event Mode is set to Time.

Bathy Sampling Rate:

Describe the digital data output rate. Enter up to 12 characters e.g. "1/second".

Sound Velocity m/sec:

Read from Propagation Velocity Used field as defined in DbSetup - Echosounder System. 
In meters per second.

Bathy Datum:

Select which datum was used for the survey:

00 - No correction applied
01 - Lowest normal low water
02 - Mean lower low water
03 - Lowest low water
04 - Mean lower low water spring
05 - Indian spring low water
06 - Mean low water spring
07 - Mean sea level
08 - Mean low water
09 - Equatorial spring low water
10 - Tropic lower low water
11 - Lowest astronomical tide
88 - Other, specify in Add. Doc.

Interpolation Scheme:

This field allows for a description of the interpolation scheme used, should some of the data records contain interpolated values (e.g., "5-MINUTE INTERVALS AND PEAKS AND TROUGHS").
Enter up to 56 characters.

13

Magnetics Digitizing Rate (second):

Output rate of digital data in seconds as read from Event Interval entered in Controller - Settings - Session Setup - Fixing when Event Mode is set to Time.

Magnetics Sampling Rate:

Describe the digital data output rate.
Enter up to 12 characters e.g. "1/second".

Sensor Tow Distance (meters):

Enter the nominal distance from the navigation reference to the leading sensor.
In meters. Enter up to 4 integers.

Estimated Sensor Depth (meters):

Enter the nominal depth of the leading magnetic sensor.
In meters. Enter up to 5 real numbers.

Horizontal Sensor Separation (meters):

Enter the nominal separation distance between the two sensors (if a second sensor is used).
In meters. Enter up to 3 integers.

Reference Field Code:

This is the reference field used to determine the residual magnetics. The primary goal in the reduction of magnetic survey data is the accurate determination of the residual (or anomalous) magnetic field associated with the geological structures or ferrous artifacts being investigated.
A magnetic anomaly (or residual) can be defined as the difference between the observed and computed (regional) magnetic field values.

Various models to simulate the patterns of the earth's geo­magnetic field have been proposed. Because the Earth's magnetic field is constantly changing, models are periodically updated.
Choose the reference field applicable to the survey:

00 - Unused
01 - AWC 70 (American World Chart model for 1970)
02 - AWC 75 (American World Chart model for 1975)
03 - IGRF-65 (International Geomagnetic Reference Field 1965)
04 - IGRF-75 (International Geomagnetic Reference Field 1975)
05 - GSFC-1266 (Goddard Space Flight Center)
06 - GSFC (POGO) 0674
07 - UK 75
08 - POGO 0368 (Polar Orbiting Geophysical Observatory 1960)
09 - POGO 1068 (Polar Orbiting Geophysical Observatory 1960)
10 - POGO 0869 (Polar Orbiting Geophysical Observatory 1960)
11 - IGRF-80 (International Geomagnetic Reference Field 1980)
12 - IGRF-85 (International Geomagnetic Reference Field 1985)
13 - IGRF-90 (International Geomagnetic Reference Field 1990)
14 - IGRF-95 (International Geomagnetic Reference Field 1995)
88 - Other, specify

Reference Field:

The selection made for 'Reference Field Code' is repeated here.

Applying Residual Field Method:

The procedure used in applying this reduction to the data.
(e.g., "LINEAR INTERP. in 60-mile SQUARE")

18

Additional Documentation:

Information concerning the survey not contained in header fields.

19

Additional Documentation:

Information concerning the survey not contained in header fields.

20

Additional Documentation:

Information concerning the survey not contained in header fields.

21

Additional Documentation:

Information concerning the survey not contained in header fields.

22

Additional Documentation:

Information concerning the survey not contained in header fields.

23

Additional Documentation:

Information concerning the survey not contained in header fields.

24

Additional Documentation:

Information concerning the survey not contained in header fields.

01

RECORD TYPE

Change from "1" to "4"

01

FILE CREATION DATE

Change to include century
From 6 digits (col 32-37) to 8 digits (col 32-39)

01

SOURCE INSTITUTION

Change from 41 chars (col 38-78) to 39 chars (col 40-78)

04

SURVEY DEPARTURE DATE

Change to include century
From 6 digits (col 1-6) to 8 digits (col 1-8)

04

PORT OF DEPARTURE

Change from 34 chars (col 7-40) to 32 chars (col 9-40)

04

SURVEY ARRIVAL DATE

Change to include century
From 6 digits (col 41-46) to 8 digits (col 41-48)

04

PORT OF ARRIVAL

Change from 32 chars (col 47-78) to 30 chars (col 49-78)

1

1

int

RECORD TYPE - Set to "4"

2-9

8

char

SURVEY IDENTIFIER
Identifier supplied by the contributing organization, else given by NGDC in a manner which represents the data. Identical to that in data record.

10-14

5

char

FORMAT ACRONYM - Set to"MGD77"

15-22

8

char

DATA CENTER FILE NUMBER
Survey identifier bestowed by the data center. First 2 chars indicate the source, first 4 indicate platform.

27-31

5

int

PARAMETERS SURVEYED CODE
Status of geophysical parameters for this survey.

Col.     Parameter Surveyed
27        bathymetry
28        magnetics
29        gravity
30        high-resolution seismics
31        deep penetration seismics
-----------------------------------------------
CODE - (for columns 27-31)
0 or blank - unspecified   
1 - Parameter NOT surveyed
3 - Parameter surveyed, not in file
5 - Parameter surveyed, in file

32-39

8

int

FILE CREATION DATE (YYYYMMDD)
Date data records were last altered (including century).

40-78

39

char

SOURCE INSTITUTION
Organization which collected the data. Include contributor if different from collector.

79-80

2

int

SEQUENCE NUMBER - Set to "01"

1-18

18

char

COUNTRY

19-39

21

char

PLATFORM NAME

40

1

int

PLATFORM TYPE CODE
0 - Unspecified
1 - Surface ship
2 - Submersible ship
3 - Aircraft
4 - Buoy
5 - Mobile land
6 - Fixed land
7 - Deep tow
8 - Anchored seafloor instrument
9 - Other, specify

41-46

6

char

PLATFORM TYPE (e.g., "SHIP","PLANE", "SUB", etc.)

47-78

32

char

CHIEF SCIENTIST(S)

79-80

2

int

SEQUENCE NUMBER - Set to "02"

1-58

58

char

PROJECT (e.g., "SURVOPS 6-69", "INDOPAC, Leg3")

59-78

20

char

FUNDING (i.e. agency or institution)

79-80

2

int

SEQUENCE NUMBER - Set to "03"

1-8

8

int

SURVEY DEPARTURE DATE (YYMMDD)

9-40

32

char

PORT OF DEPARTURE (i.e. city, country)

41-48

8

int

SURVEY ARRIVAL DATE (YYMMDD)

49-78

30

char

PORT OF ARRIVAL (i.e. city, country)

79-80

2

int

SEQUENCE NUMBER - Set to "04"

1-40

40

char

NAVIGATION INSTRUMENTATION (e.g. "SAT/LORAN A/SEXTANT")

41-78

38

char

GEODETIC DATUM/POSITION DETERMINATION METHOD (e.g. "WGS84/PRIM - SATELLITE, SEC-LORAN A")

79-80

2

int

SEQUENCE NUMBER - Set to "05"

1-40

40

char

BATHYMETRY INSTRUMENTATION
Include information such as frequency, beam width, and sweep speed of recorder.

41-78

38

char

ADDITIONAL FORMS OF BATHYMETRIC DATA (e.g., "MICROFILM","ANALOG RECORDS")

79-80

2

int

SEQUENCE NUMBER - Set to "06"

1-40

40

char

MAGNETICS INSTRUMENTATION (e.g., "PROTON PRECESSION MAG-GEOMETRICS G-801")

41-78

38

char

ADDITIONAL FORMS OF MAGNETICS DATA (e.g., "PUNCH TAPE","ANALOG RECORDS")

79-80

2

int

SEQUENCE NUMBER - Set to "07"

1-40

40

char

GRAVITY INSTRUMENTATION (e.g., "L and R S-26")

41-78

38

char

ADDITIONAL FORMS OF GRAVITY DATA (e.g., "MICROFILM", "ANALOG RECORDS")

79-80

2

int

SEQUENCE NUMBER - Set to "08"

1-40

40

char

SEISMIC INSTRUMENTATION
Include the size of the sound source, the recording frequency filters, and the number of channels (e.g., "1700 cu. in., AIRGUN, 8-62 Hz, 36 CHANNELS")

41-78

38

char

FORMATS OF SEISMIC DATA (e.g., "DIGITAL", "MICROFILM", "NEGATIVES", etc.)

79-80

2

int

SEQUENCE NUMBER - Set to "09"

1

1

char

FORMAT TYPE
Set to "A", which means format contains integers, floating points, and alphanumerics

2-76

38

char

FORMAT DESCRIPTION
This is one method of reading (not writing) the data in FORTRAN. Set to the following:
"(I1,A8,I3,I4,3I2,F5.3,F8.5,F9.5,I1,F6.4,F6.1,I2,I1,3F6.1,I1,F5.1,F6.0,F7.1,"
(NOTE: continued in sequence no. 11)

79-80

2

int

SEQUENCE NUMBER - Set to "10"

1-19

19

char

FORMAT DESCRIPTION Continued
set to following: "F6.1,F5.1,A5,A6,I1)"

41-43

3

int

TOPMOST LATITUDE OF SURVEY **
(to next whole degree)

44-46

3

int

BOTTOMMOST LATITUDE

47-50

4

int

RIGHTMOST LONGITUDE

51-54

4

int

LEFTMOST LONGITUDE

70-80

2

int

SEQUENCE NUMBER - Set to "11"

1-3

3

real

GENERAL DIGITIZING RATE OF BATHYMETRY
In tenths of minutes.
The rate which is present within the data records (e.g., if values were coded every 5 minutes, set to "050")

4-15

12

char

GENERAL SAMPLING RATE OF BATHYMETRY
This rate is instrumentation dependent (e.g., "1/SECOND")

16-20

5

real

ASSUMED SOUND VELOCITY
In tenths of meters per second.
Historically, in the U.S., this speed has been 800 fathoms/sec, which equals 1463.0 meters/sec.; however, some recorders have a calibration of 1500 meters/sec (e.g., "14630")

21-22

2

int

BATHYMETRIC DATUM CODE
00 - No correction applied
01 - Lowest normal low water
02 - Mean lower low water
03 - Lowest low water
04 - Mean lower low water spring
05 - Indian spring low water
06 - Mean low water spring
07 - Mean sea level
08 - Mean low water
09 - Equatorial spring low water
10 - Tropic lower low water
11 - Lowest astronomical tide
88 - Other, specify in Add. Doc.

23-78

56

char

INTERPOLATION SCHEME
This field allows for a description of the interpolation scheme used, should some of the data records contain interpolated values (e.g., "5-MINUTE INTERVALS AND PEAKS AND TROUGHS").

79-80

2

int

SEQUENCE NUMBER - Set to "12"

1-3

3

real

GENERAL DIGITIZING RATE OF MAGNETICS
In tenths of minutes.
The rate which is present within the data records.

4-5

2

int

GENERAL SAMPLING RATE OF MAGNETICS                                                         In seconds.
This rate is instrumentation dependent (e.g., if the pulse rate is every 3 sec, set to "03")

6-9

4

int

MAGNETIC SENSOR TOW DISTANCE
In meters.
The distance from the navigation reference to the leading sensor.

10-14

5

real

SENSOR DEPTH
In tenths of meters.
This is the estimated depth of the lead magnetic sensor.

15-17

3

int

HORIZONTAL SENSOR SEPARATION
In meters. 
If two sensors are used.

18-19

2

int

REFERENCE FIELD CODE
This is the reference field used to determine the residual magnetics:
00 - Unused
01 - AWC 70
02 - AWC 75
03 - IGRF-65
04 - IGRF-75
05 - GSFC-1266
06 - GSFC (POGO) 0674
07 - UK 75
08 - POGO 0368
09 - POGO 1068
10 - POGO 0869
11 - IGRF-80
12 - IGRF-85
13 - IGRF-90
14 - IGRF-95
88 - Other, specify

20-31

12

char

REFERENCE FIELD
(e.g., "IGRF-85")

32-78

47

char

METHOD OF APPLYING RESIDUAL FIELD
The procedure used in applying this reduction to the data
(e.g., "LINEAR INTERP. in 60-mile SQUARE")

79-80

2

int

SEQUENCE NUMBER - Set to "13"

1-3

3

real

GENERAL DIGITIZING RATE OF GRAVITY
In tenths of minutes.
The rate present within the data records

4-5

2

int

GENERAL SAMPLING RATE OF GRAVITY
In seconds.
This rate is instrumentation dependent. If recording is continuous, set to "00"

6

1

int

THEORETICAL GRAVITY FORMULA CODE
1 - Heiskanen 1924
2 - International 1930
3 - IAG System 1967
4 - IAG System 1980
8 - Other, specify

7-23

17

char

THEORETICAL GRAVITY FORMULA
(e.g., "INTERNATIONAL '30", "IAG SYSTEM (1967)", etc.)

24

1

int

REFERENCE SYSTEM CODE
Identifies the reference field:
1 - Local system, specify
2 - Potsdam system
3 - System IGSN 71
9 - Other, specify

25-40

16

char

REFERENCE SYSTEM
(e.g., "POTSDAM SYSTEM", "SYSTEM IGSN 71", etc.)

41-78

38

char

CORRECTIONS APPLIED
Drift, tare and bias corrections applied. (e.g., "+0.075 MGAL PER DAY")

79-80

2

int

SEQUENCE NUMBER - Set to "14"

1-7

7

real

DEPARTURE BASE STATION GRAVITY
In tenths of milligals.
At sea level (Network value preferred.)

8-40

33

char

DEPARTURE BASE STATION DESCRIPTION
Indicates name and number of station

41-47

7

real

ARRIVAL BASE STATION GRAVITY
In tenths of milligals.
At sea level (Network value preferred.)

48-78

31

char

ARRIVAL BASE STATION DESCRIPTION
Indicates name and number of station

79-80

2

int

SEQUENCE NUMBER - Set to "15"

1-2

2

int

NUMBER OF 10-DEGREE IDENTIFIERS **
This is the number of 4-digit 10-degree identifiers, excluding the "9999" flag, which will follow this field. (see APPENDIX A)

4-78

75

int

10-DEGREE IDENTIFIERS
A series of 4-digit codes, separated by commas, which identify the 10-degree squares through which the survey collected data (see APPENDIX A).
Code "9999" after last identifier.

79-80

2

int

SEQUENCE NUMBER - Set to "16"

1-75

75

int

10-DEGREE IDENTIFIERS
Continued

79-80

2

int

SEQUENCE NUMBER - Set to "17"

1-78

75

int

ADDITIONAL DOCUMENTATION
information concerning this survey not contained in header fields.

79-80

2

int

SEQUENCE NUMBER - Set to "18 thru 24"

DATA-RECORD TYPE

Change from "3" to "5" (col 1)

TIME ZONE CORRECTION

Change from hundredths of hours to hours
From 5 digits (col 10-14) to 3 digits (col 10-12)

YEAR

Change to include century
From 2 digits (col 15-16) to 4 digits (col 13-16)

1

1

int

DATA RECORD TYPE:
Set to "5" (data record.) 

2-9

8

char

SURVEY IDENTIFIER:
Identifier supplied by the contributing organization, else given by NGDC in a manner which represents the data. Identical to that in header record.

10-12

3

int

TIME-ZONE CORRECTION:
In hours. Corrects time (in characters 13-27) to GMT when added: equals zero when time is GMT.  Timezone normally falls between -13 and +12 inclusively.

13-16

4

int

YEAR:
including century (e.g. 1972)

17-18

2

int

MONTH:
(e.g. May is represented as 05)

19-20

2

int

Day:
Day of month

21-22

2

int

HOUR:
Hour of day

23-27

5

real

MINUTES x 1000

28-35

8

real

LATITUDE x 100000
+ = North; - = South
Between -90 and +90 degrees

36-44

9

real

LONGITUDE x 100000
+ = East; - = West
Between -180 and +180 degrees

45

1

int

POSITION TYPE CODE:
Indicates how Lat/Long was obtained
1 = Observed fix
3 = Interpolated
9 = Unspecified

46-51

6

real

BATHYMETRY, 2-WAY TRAVEL TIME:
In ten-thousandths of seconds
Corrected for transducer depth and other such corrections, especially in shallow water

52-57

6

real

BATHYMETRY, CORRECTED DEPTH:
In ten-thousandths of meters

58-59

2

int

BATHYMETRIC CORRECTION CODE:
This code details the procedure used for determining the sound velocity correction to depth:
01-55        Matthews' Zones with zone
59             Matthews' Zones, no zone
60             S. Kuwahara Formula  
61             Wilson Formula
62             Del Grosso Formula     
63             Carter's Tables  
88             Other (see Add. Doc.)
99             Unspecified 

60

1

int

BATHYMETRIC TYPE CODE:
Indicates how the bathymetric value was obtained -
1 = Observed
3 = Interpolated (Heade Sq. 12)
9 = Unspecified

61-66

6

real

MAGNETICS TOTAL FIELD, 1ST SENSOR:

In tenths of nanoteslas (gammas).
For leading sensor. Use this field for single sensor.

67-72

6

real

MAGNETICS TOTAL FIELD, 2ND SENSOR:

In tenths of nanoteslas (gammas).
For trailing sensor.

73-78

6

real

MAGNETICS RESIDUAL FIELD:
In tenths of nanoteslas (gammas).
The reference field used is in Header Seq. 13.

79

1

int

SENSOR FOR RESIDUAL FIELD:
1 - 1st or leading sensor
2 - 2nd or trailing sensor
9 - Unspecified

80-84

5

real

MAGNETICS DIURNAL CORRECTION:
In tenths of nanoteslas (gammas).
If  9-filled (i.e., set to "+9999"), total and residual fields are assumed to be uncorrected; if used, total and residuals are assumed to have been already corrected.

85-90

6

int

DEPTH/ALTITUDE OF MAGNETICS SENSOR:

In meters.
+ = Below sealevel      - = Above sealevel

91-97

7

real

OBSERVED GRAVITY:
In tenths of milligals.
Corrected for Eotvos, drift, and tares

98-103

6

real

EOTVOS CORRECTION:
In tenths of milligals.
E = 7.5 V cos(phi) * sin(alpha) + 0.0042 V*V

104-108

5

real

FREE-AIR ANOMALY:
In tenths of milligals.
Free-air Anomaly = G(observed) minus G(theoretical)

109-113

5

char

SEISMIC LINE NUMBER:
Used for cross referencing with seismic data.

114-119

6

char

SEISMIC SHOT-POINT NUMBER:

120

1

int

QUALITY CODE FOR NAVIGATION:
5 - Suspected, by the contributor
6 - Suspected, by the data center
9 - No identifiable problem found
(NOTE - Institution will most frequently 9-fill this field; however, should they wish to code a "5", the data center will not contradict.  The data center's quality control program, which performs (among other checks) a vectorial analysis of the navigation, is available in a printout form upon request.)

1

North

East

3

South

East

5

South

West

7

North

West

37 deg 48'S, 4 deg 13'E

3

3

0

0

21.6 deg S, 14.3 deg W

5

2

0

1

34 deg 28'N, 143 deg 27'W

7

3

1

4

75 deg N, 43 deg E

1

7

0

4