Bathymetry Trackline Data from CEAREX

1. Bathymetry Data Description

Bathymetry data on this CD-ROM include two types of files: tracklines and gridded data. The gridded data are described in the file \BATHY\GRIDS.DOC, and contained in the file \BATHY\MANLEY.BTH.

Bathymetry tracklines included here are from three sources: the ship NORTHWIND while it was enroute to the CEAREX area near Svalbard [file \BATHY\NWIND.BTH]; the acoustics camp (A-Camp) located on an ice floe [file \BATHY\ACAMP.BTH]; and a group of tracks collected during the drift phase of CEAREX [\BATHY\TRACKS.BTH].

The data were provided by the investigators to the Naval Research Laboratory where they were formatted for submission to the NOAA National Geophysical Data Center Marine Geology and Geophysics Division (MGG), for the marine geophysical data base maintained there. MGG ingested the trackline data and provided files for this CD-ROM in their Marine Geophysical Data Exchange Format, "MGD77". Please note that the header for the file ACAMP.BTH was added at NSIDC, and may contain more information after it has been ingested by MGG.

There is also another file, \BATHY\OCAMP.BTH, containing data from the oceanography camp (O-Camp) provided by D. Menemenlis of the Institute of Ocean Sciences, Sidney, BC. These data were intended for inclusion in the "MGD77" format files. However, it is not certain that they were actually included. The data are provided separately in a file that contains descriptive text, as well as being incorporated as Section 3 of this file to ensure they are available for use. These data will be incorporated into the bathymetry data set on the next version or volume of the Eastern Arctic CD-ROM series. NSIDC apologizes for any inconvenience this may cause.

2. Data Format

2.1. Comments Requested

The format "MGD77" has been used to present these tracklines because no other "standard" format was available. The user community is invited to comment on the utility of this format for data analysis. It appears that a gridded format may be more useful; as the set of available tracklines for the Eastern Arctic grows, the feasibility of gridding the data will be investigated, for inclusion on possible future CD-ROMs.

2.2. The Marine Geophysical Data Exchange Format - 'MGD77'

The text describing the MGD77 format is extracted from "The Marine Geophysical Data Exchange Format" - 'MGD77' (Bathymetry, Magnetics, and Gravity), Key to Geophysical Records Documentation no. 10 (revised February 1989) compiled by the MGD77 Task Group, A.M. Hittelman, Chairman. The 16-page document is available on request from: NOAA/National Geophysical Data Center, 325 Broadway, Boulder, CO 80303 USA.

2.3. Header Record Format

"MGD77" uses 16 header records composed of 80-character "sequences" that are used to describe the data. A "sequence" is a logical record that ends with its sequence number in positions 79-80. The 120-character physical records are composed of 1.5 sequences each. The header sequences are defined in the table that follows.

MGD77 Header Record Content and Format

      column   field   Fortran   description
      numbers  length  format    of contents
      -------  ------  --------  --------------------------------  
Sequence No. 1:
        1         1    I1        Record type - set to "1"
       2-9        8    A8        Cruise id as it appears in data record
      10-14       5    A5        Format acronym - set to "MGD77"
      15-22       8    I8        Data Center file number 
      23-26       4    4X        Blanks      
      27-31       5    5I1       Code for parameters surveyed: 
                                   col. no.     parameter
                                   --------     ------------------------
                                     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 contained in file
                                   5 parameter surveyed, contained in file

      32-37       6    3I2       File creation date
      38-78       41   A41       Contributing institution
      79-80       2    I2        Sequence no. (set to "01")

Sequence No. 2:
      1-18        18    A18      Country
      19-39       21    A21     Platform name
       40         1     I1      Platform type code (only codes used here
                                 are presented):
                                Code for column 40:
                                   0 unspecified
                                   1 surface ship
                                   4 buoy
                                   9 other (used for "ice floe" in the 
                                             file "ACAMP.BTH")
      41-46       6      A6     Platform type (ship, seaice)
      47-78       32     A32    Chief scientist(s)
      79-80       2      I2     Sequence no. (set to "02")

Sequence No. 3:
      1-58        58     A58    Project, cruise and leg
      59-78       20     A20    Funding agency or institution
      79-80       2      I2     Sequence no. (set to "03")

Sequence No. 4: 
      1-6         6      3I2    Survey departure date (YYMMDD)
      7-40        34     A34    Port of departure
      41-46       6      3I2    Survey arrival date (YYMMDD)
      47-78       32     A32    Port of arrival
      79-80       2      I2     Sequence no. (set to "04")

Sequence No. 5:
      1-40        40      A40   Navigation instrumentation
      41-78       38      A38   Position determination method
      79-80       2       I2    Sequence no. (set to "05")

Sequence No. 6:
      1-40        40       A40   Bathymetry instrumentation
      41-78       38       A38   Additional forms of bathymetry data
                                   (microfilm, analog, etc.)
      79-80        2       I2    Sequence no. (set to "06")

Sequence No. 7: Magnetics  1-80  blanks
Sequence No. 8: Gravity 1-80 blanks
Sequence No. 9: Seismicity 1-80 blanks

Sequence No. 10: 
        1          1        A1    Format type - set to "A" (format contains 
                                  integers, floating points and alphanumerics)
       2-75        74       A74   Format description: this is one method of 
                                  reading (not writing) the data in Fortran.  
                                  The format is continued in Sequence no. 11.
      76-78        2        2X    Blanks
      79-80        2        I2    Sequence no. (set to "10")

Sequence No. 11:
      1-17         17       A17   Format description, continued.
      18-40        23       23X   Blanks
      41-43        3        I3    Topmost latitude of cruise
                                                    (to next whole degree)
      44-46        3        I3    Bottommost latitude of cruise      "
      47-50        4        I4    Leftmost longitude of cruise       "
      51-54        4        I4    Rightmost latitude of cruise       "
      55-78        24       24X   Blanks
      79-80        2        I2    Sequence no. (set to "11")

Sequence No. 12: 
       1-3         3         F3.1   General digitizing rate of bathymetry
                                       - in minutes
       4-15        12        A12    General sampling rate of bathymetry
                                       (instrumentation-dependent)
      16-20        5         F5.1   Assumed sound velocity, accurate to
                                       0.1 meter/second
      21-22        2         I2     Bathymetric datum code:
                                    00 no correction applied (sea level)
                                    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
                                    09 Equatorial spring low water
                                    10 Tropic lower low water
                                    11 lowest astronomical tide
                                    88 other (specified in sequences 18-24)
      23-78      56           A56   Interpolation scheme, if any was used
      79-80      2            I2    Sequence no. (set to "12")
 
Sequence No. 13: Magnetics - 80 blanks 
Sequence No. 14: Gravity - 80 blanks
Sequence No. 15: Gravity - 80 blanks

Sequence No. 16: 
       1-2       2             I2    Number of 4-digit 10-degree identifiers 
                                       that will follow this field.
        3        1             X     Blank
       4-78      75      15(I4, 1X)  10-degree identifiers: series of 4-digit 
                                       codes, separated by commas, that 
                                       identify the 10-degree squares through 
                                       which the survey collected data.  Code 
                                       "9999" follows last identifier.  An 
                                       index of the 10-degree squares is
                                       provided in the complete documentation 
                                       "Marine Geophysical Data Exchange 
                                       Format" - 'MGD77', available on request 
                                       from NOAA/NGDC/MGG or from NSIDC.
      79-80     2             I2     Sequence no. (set to "16")

Sequence No. 17:
       1-75     75       15(I4, 1X)  10-degree identifiers, continued.
      76-78     3             3X     Blanks
      79-80     2             I2     Sequence no. (set to "17")

Sequence No. 18 - 24: Additional Documentation  - seven sets of 80 blanks 
are in the data files presented here.

2.4. Data Record Format

Data records are 120-character records with contents and format described in the table below. Unused fields are filled with 9's.

MGD77 Data Record Content and Format

     column   field   Fortran   description
     numbers  length  format    of contents
     -------  ------  --------  --------------------------------  
        1       1       I1      Data record type - all data records defined 
                                  as and set to "3".
       2-9      8       A8      Cruise id - identical to col. 2-9 in
                                  header sequence no. 01.
      10-14     5       F5.2    Time-zone correction - corrects survey
                                  time (coded in columns 15-27) to GMT; equals
                                  zero if survey time is GMT.  Time zone 
                                  normally between -13 and +12, inclusively.
      15-16     2       I2      Year (YY)
      17-18     2       I2      Month (MM)
      19-20     2       I2      Day (DD)
      21-22     2       I2      Hour (HH)
      23-27     5       F5.3    Minutes
      28-35     8       F8.5    Latitude (+ =North, - =South)
      36-44     9       F9.5    Longitude between -180 and 180 
                                  (+=East, - =West)
       45       1       I1      Position type code (how navigation 
                                  was obtained)
                                 1 = observed fix
                                 3 = interpolated
                                 9 = unspecified
      46-51     6       F6.4    Bathymetry, travel time - 2-way travel time 
                                  in seconds corrected for transducer depth 
                                  and other such corrections, especially in 
                                  shallow water.
      52-57     6       F6.1    Bathymetry, corrected depth, meters
      58-59     2       I2      Bathymetry correction code - details the 
                                  procedure used for determining the sound
                                  velocity correction to depth:
                                  01-55  Matthews' Zone - use only if
                                         Matthews' Zones were used to correct
                                           depth.
                                  59     Matthews' corrections used but
                                           zones unspecified in data record.
                                  60     S.Kuwahara Formula
                                  61     Wilson Formula
                                  62     Del Grosso Formula
                                  63     Carter's Tables
                                  88     Other (described in sequence no. 
                                           18-24 of header)
                                  99     Unspecified
        60      1       I1      Bathymetry type code - how the bathymetric 
                                 value was obtained:
                                   1 = observed
                                   3 = interpolated (scheme described in
                                         header sequence no. 12)
                                   9 = unspecified
      61-119    59       59X    Unused data fields for seismics and magnetics.
                                  Filled with 9's in these data sets.
       120      1        I1     Quality code for navigation:
                                  5 = suspected, by the originating
                                        institution
                                  6 = suspected, by the data center
                                  9 = no identifiable problem found.  
                                 A vectorial analysis of the navigation, 
                                 from the data center's quality control 
                                 program, is available in printout form on 
                                 request.

To use the data in a program, read consecutive strings of 80 characters in the order described in the Header and Data Record tables above.

3. CEAREX Oceanography Camp Fathometer Readings, Dimitris Menemenlis, Institute of Ocean Sciences.

[Data described and presented here were intended for inclusion in the bathymetry track line data files on this CD-ROM. At "press time", it is not certain that these data were actually made part of the track line data files. To assure their availability, the data are presented in this text file. They MAY be duplicated in the files in the directory \BATHYMET. When the Eastern Arctic bathymetry data base is updated, these data will be included in the next version. NSIDC apologizes for any inconvenience this may cause to the data users.]

A 12 kHz EDO transducer, a GIFFT transceiver and an oscilloscope were used to periodically measure the depth of the water column at the CEAREX "O" Camp. A mean sound speed of 1492 m/s is assumed in order to convert the travel time of the acoustic signal (echo) to depth. Camp navigation is interpolated from approximately hourly satellite fixes.

date           UTC      day         lat N    long E   echo(s)  depth(m)

30 march 89    13:16     89.5528    83.064    9.887   5.399    4028
31 march 89    18:30     90.7708    83.036    9.977   5.121    3820
01 april 89    17:30     91.7292    83.023   10.260   5.320    3969
02 april 89    14:30     92.6042    82.986   10.522   5.225    3898
03 april 89    08:30     93.3542    82.919   10.607   5.008    3736
04 april 89    16:00     94.6667    82.875   10.620   4.845    3614
05 april 89    19:25     95.8090    82.858   10.587   4.816    3593
06 april 89    23:55     96.9965    82.807   10.468   4.504    3360
07 april 89    11:55     97.4965    82.787   10.525   4.060    3029
08 april 89    12:00     98.5000    82.759   10.637   3.749    2797
09 april 89    10:00     99.4167    82.731   10.614   3.399    2536
10 april 89    12:00    100.5000    82.710   10.715   3.113    2322
11 april 89    06:42    101.2792    82.706   10.714   3.017    2251
11 april 89    19:03    101.7938    82.710   10.838   3.040    2268
12 april 89    06:44    102.2806    82.681   10.856   2.740    2044
12 april 89    18:55    102.7882    82.641   10.476   2.212    1650
13 april 89    06:59    103.2910    82.649    9.951   2.869    2140
13 april 89    13:09    103.5479    82.653    9.812   3.174    2368
13 april 89    18:53    103.7868    82.646    9.646   3.299    2461
13 april 89    22:01    103.9174    82.647    9.543   3.314    2472
14 april 89    06:55    104.2882    82.648    9.337   3.446    2571
14 april 89    12:32    104.5222    82.651    9.251   3.753    2800
14 april 89    19:21    104.8063    82.645    9.071   3.599    2685
14 april 89    22:52    104.9528    82.648    8.978   3.619    2700
15 april 89    07:05    105.2951    82.658    8.880   3.678    2744
15 april 89    14:52    105.6194    82.656    8.889   3.666    2735
15 april 89    19:02    105.7931    82.647    8.889   3.617    2698
15 april 89    22:54    105.9542    82.643    8.886   3.418    2550
16 april 89    06:53    106.2868    82.637    8.887   3.484    2599
16 april 89    14:02    106.5847    82.625    8.939   3.178    2371
16 april 89    18:50    106.7847    82.611    8.928   2.866    2138
17 april 89    00:57    107.0396    82.594    8.927   2.704    2017
17 april 89    06:51    107.2854    82.584    8.898   2.579    1924
17 april 89    13:11    107.5493    82.571    8.867   2.433    1815
17 april 89    18:52    107.7861    82.550    8.741   2.247    1676
17 april 89    23:08    107.9639    82.535    8.625   2.193    1636
18 april 89    07:01    108.2924    82.526    8.483   2.343    1748
18 april 89    13:22    108.5569    82.512    8.354   2.556    1907
18 april 89    18:57    108.7896    82.506    8.270   2.524    1883
19 april 89    00:55    109.0382    82.500    8.093   2.603    1942
19 april 89    06:51    109.2854    82.499    8.030   2.548    1901
19 april 89    16:45    109.6979    82.494    7.894   2.556    1907
19 april 89    18:49    109.7840    82.492    7.858   2.595    1936
20 april 89    01:16    110.0528    82.487    7.751   2.835    2115
20 april 89    06:56    110.2889    82.484    7.702   2.929    2185
20 april 89    12:38    110.5264    82.471    7.580   3.355    2503
20 april 89    18:58    110.7903    82.468    7.461   3.658    2729
20 april 89    23:28    110.9778    82.464    7.375   3.909    2916
21 april 89    06:55    111.2882    82.459    7.326   4.059    3028
21 april 89    13:00    111.5417    82.452    7.252   4.218    3147
21 april 89    18:49    111.7840    82.449    7.205   4.256    3175
22 april 89    06:56    112.2889    82.441    7.142   4.259    3177
22 april 89    19:06    112.7958    82.415    6.954   3.724    2778
22 april 89    22:24    112.9333    82.406    6.877   3.314    2472
23 april 89    07:08    113.2972    82.390    6.746   3.241    2418
23 april 89    18:58    113.7903    82.366    6.394   3.542    2642
24 april 89    06:50    114.2847    82.364    6.187   3.492    2605
24 april 89    15:23    114.6410    82.353    6.052   3.267    2437
24 april 89    18:50    114.7847    82.354    5.983   3.161    2358
24 april 89    23:54    114.9958    82.354    5.861   3.039    2267

4. Reference

MGD77 Task Group (1989) Key to Geophysical Records Documentation no. 10 (revised): Marine Geophysical Data Exchange Format - 'MGD77' (Bathymetry, Magnetics, and Gravity), 16 p. NOAA, National Geophysical Data Center, 16 p.

5. Acknowledgments:

NSIDC would like to thank John Griffin, John Campagnoli and Dan Metzger of NOAA, National Geophysical Data Center, Marine Geology and Geophysics Division, for their assistance in the final compilation and formatting of the trackline data. Norman Cherkis of NRL collected data from the several investigators and from his own data base, and provided it to NGDC/MGG for ingest there; we thank him for his contribution.

6. Contact Information

Dr. Arthur B. Baggeroer (A camp)
Massachusetts Institute of Technology
Building 5-204
77 Massachusetts Avenue
Cambridge, MA 01239
Telephone: 617-253-4336
Telemail: A.BAGGEROER/Omnet
Internet: abb@arctic.mit.edu

Norman Z. Cherkis (data collection, ingest)
Naval Research Laboratory
Code 5110
Washington, DC 20375-5000 USA
Telephone: 202-767-2024

Dr. Dimitris Menemenlis (O camp)
Institute of Ocean Sciences
P.O. Box 6000
Sydney, BC V8L 4B2
Telephone: (604) 356-6339

NOAA, National Geophysical Data Center (MGD77 format)
Marine Geology and Geophysics Division
325 Broadway
Boulder, CO 80303
Telephone: 303-497-6542

Dr. Keith von der Heydt (A camp) Woods Hole Oceanographic Institution Woods Hole, MA 02543 Telephone: 508-457-2000 Telemail: K.VONDERHEYDT/Omnet Internet: kvdh@polar.whoi.edu

August 1991