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
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