u671at.m77t - MGD77 data file for Geophysical data from field activity 71006 (U-6-71-AT) in Liberia to Puerto Rico, Atlantic Ocean from 11/24/1971 to 12/09/1971

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Frequently anticipated questions:

What does this data set describe?

Title:
u671at.m77t - MGD77 data file for Geophysical data from field activity 71006 (U-6-71-AT) in Liberia to Puerto Rico, Atlantic Ocean from 11/24/1971 to 12/09/1971
Abstract:
Single-beam bathymetry, gravity, and magnetic data along with DGPS navigation data was collected as part of field activity 71006 (U-6-71-AT) in Liberia to Puerto Rico, Atlantic Ocean from 11/24/1971 to 12/09/1971, http://walrus.wr.usgs.gov/infobank/u/u671at/html/u-6-71-at.meta.html
These data are reformatted from space-delimited ASCII text files located in the Coastal and Marine Geology Program (CMGP) InfoBank field activity catalog at http://walrus.wr.usgs.gov/infobank/u/u671at/html/u-6-71-at.bath.html http://walrus.wr.usgs.gov/infobank/u/u671at/html/u-6-71-at.grav.html and http://walrus.wr.usgs.gov/infobank/u/u671at/html/u-6-71-at.mag.html into MGD77T format provided by the NOAA's National Geophysical Data Center(NGDC). The MGD77T format includes a header (documentation) file (.h77t) and a data file (.m77t). More information regarding this format can be found in the publication listed in the Cross_reference section of this metadata file.
Supplemental_Information:
The navigation data are digitally collected using a Satellite Integrated Navigation (SINS) system. The system is a space-based satellite navigation maintained by the United States government and is accessible using a satellite receiver. This system provides navigational accuracy of approximately 200 m.The Data Acquistion, Processing, and Storage (DAPS) group performs a number of processing steps to the navigation data once it is collected which can vary by cruise. These steps are outlined within the header information in each individual digital navigation (.05x) space-delimited ASCII data file. The header information rows are indicated by lines beginning with the character "!". There is no information on how the single-beam bathymetry, gravity, and magnetic data were collected. For each data gathering cruise leg, the available data in the following categories are forwarded to NGDC: navigation, gravity, magnetics, bathymetry, and seismic shot points. The available data for each cruise leg are re-formatted and combined into the Marine Geophysical Data Exchange Format (MGD77) and into the internal NGDC SEIS-NAV format by USGS using several USGS developed FORTRAN programs.The FORTRAN programs sample the navigation to every integer minute of the cruise. When necessary, the latitudes and longitudes are linearly interpolated. If the time between the actual navigation fixes exceeds five minutes, no data are included in the MGD77 file.To build the MGD77 file, gravity, magnetics, and bathymetry are added to this sampled navigation. When necessary, gravity, magnetics, and bathymetry data are linearly interpolated if the time between the actual data samples does not exceed five minutes. If a time gap exceeds this, the data are not reported.The navigation data are merged with the seismic shot point data in a SEIS- NAV format file. For this file, navigation data are interpolated for each shot point. Both types of files are written to magnetic tape and sent to NGDC.
  1. How might this data set be cited?
    U.S. Geological Survey, and Coastal and Marine Geology Program, 2013, u671at.m77t - MGD77 data file for Geophysical data from field activity 71006 (U-6-71-AT) in Liberia to Puerto Rico, Atlantic Ocean from 11/24/1971 to 12/09/1971: U.S. Geological Survey, Menlo Park, CA.

    Online Links:

    This is part of the following larger work.

    Steele, Wm. Clinton, Degnan, Carolyn H., Deeter, Gary B., and Riordan, Jean A., 1980, DESCRIPTION OF MARINE GEOPHYSICAL DATA COLLECTED BY THE U.S. GEOLOGICAL SURVEY AND HOW TO OBTAIN IT: U.S. Geological Survey Open File Report 167, U.S. Geological Survey, Menlo Park, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -62.96440
    East_Bounding_Coordinate: -10.90170
    North_Bounding_Coordinate: 17.69430
    South_Bounding_Coordinate: 6.03600
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 24-Nov-1971
    Ending_Date: 09-Dec-1971
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: tab-delimited ASCII text files
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference: Liberia to Puerto Rico, Atlantic Ocean
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.25722210100002.
  7. How does the data set describe geographic features?
    u671at.m77t
    MGD77T single-beam bathymetry, gravity, and magnetics data file for U671AT (Source: NOAA's National Geophysical Data Center, See Hittelman and others (2010) Cross_Reference section above for details about the MGD77T format and citation information.)
    SURVEY_ID
    Survey identifier supplied by the contributing organization (Source: NGDC) This identifier varies in format and is supplied by the contributing organization
    TIMEZONE
    Time-zone correction (Source: NGDC) In our datasets, no correction was applied. All values equal 0.
    DATE
    YYYYMMDD (Source: NGDC)
    Range of values
    Minimum:19711124
    Maximum:19711209
    Units:Year, month, day
    TIME
    Time (Source: NGDC)
    Range of values
    Minimum:0
    Maximum:2359
    Units:hours and decimal minutes
    LAT
    Latitude (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:6.036
    Maximum:17.6938
    Units:decimal degrees
    LON
    Longitude (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:-62.9627
    Maximum:-10.9017
    Units:decimal degrees
    POS_TYPE
    Indicates how lat/lon was obtained (Source: NGDC)
    Range of values
    Minimum:1
    Maximum:3
    Units:1 = observed fix, 3 = interpolated fix, nil = unspecified
    BAT_TTIME
    Bathymetry, 2-way travel time (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.05
    Maximum:7.575
    Units:seconds
    CORR_DEPTH
    Bathymetry, corrected depth (Source: U.S. Geological Survey)
    Range of values
    Minimum:38
    Maximum:5714.0
    Units:decimal meters
    BAT_CPCO
    Bathymetric Correction code - details the procedure used for determining the sound velocity correction to depth (Source: NGDC)
    Range of values
    Minimum:59
    Maximum:59
    Units:01-55 Matthews' Zones with zone , 59 Matthews' Zones, no zone specified, 60 S. Kuwahara Formula, 61 Wilson Formula, 62 Del Grosso Formula, 63 Carter's Tables, 88 Other (see Add. Doc.), 97 Computed using 1500 meters/sec, 98 Unknown if Corrected, 99 Unspecified
    BAT_TYPCO
    Bathymetry type code - indicates how the bathymetric value was obtained (Source: NGDC)
    Range of values
    Minimum:1
    Maximum:3
    Units:1 - Observed, 3 - Interpolated (Header Seq. 12), 9 - Unspecified
    MAG_TOT
    Magnetics total field - 1st sensor (Source: NGDC)
    Range of values
    Minimum:28058
    Maximum:42447.3
    Units:gammas
    MAG_RES
    Magnetics residual field field (Source: NGDC)
    Range of values
    Minimum:-3712.6
    Maximum:4950.8
    Units:gammas
    FREEAIR
    Free-air Anomaly = G(observed) minus G(theoretical) (Source: NGDC)
    Range of values
    Minimum:--308.3
    Maximum:308.2
    Units:milligals
    Entity_and_Attribute_Overview:
    Bathymetry, gravity, magnetics, and navigation data for U.S. Geological Survey bathymetry survey U671AT in MGD77T format.
    Entity_and_Attribute_Detail_Citation:
    Attributes are obtained from MGD77T data files created from the navigation and bathymetry best files. MGD77T is the standard, defined data format used for geophysical data in the National Geophysical Data Center. See Cross_Reference section above for citation details.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
    • Coastal and Marine Geology Program
  2. Who also contributed to the data set?
    Marty Kane (Chief Scientist)
  3. To whom should users address questions about the data?
    Gregory K. Miller
    U.S. Geological Survey
    Physical Scientist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 803-8747, ext. 3020 (voice)
    gmiller@usgs.gov

Why was the data set created?

These data and information are intended for science researchers,students, policy makers, and general public. These data are not to be used for navigation purposes. The data are reformatted into MGD77T standard format for inclusion into NOAA's NGDC geophysical database. From there the data will be made available to GeoMapApp ( http://www.geomapapp.org/ ) and Virtual Ocean ( http://www.virtualocean.org/ ) Earth-browsing software. Access to the data is also provided via the USGS Coastal and Marine Geoscience Data System ( http://cmgds.marine.usgs.gov/ ).

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 15-Dec-1995 (process 1 of 7)
    Navigation Data >Converted to time format with year at start. > >02/11/86 KAYE DUA0:[DATA.U671AT.N]U671AT.050; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 > Person who carried out this activity:
    U.S. Geological Survey (USGS) , Coastal and Marine Geology (CMG)
    Attn: Carolyn H. Degnan
    Geophysicist
    USGS Pacific Coastal & Marine Science Center, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7452 (voice)
    (831) 427-4748 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 31-Oct-1998 (process 2 of 7)
    Gravity Data >10/31/1998 /tiger/u/u671at/grav/u-6-71-at.161_050 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >04/22/86 CLINT DUA0:[DATA.U671AT]U671AT.161; >DRB0:[DRS.NGDC]UNREFNGDC.EXE; >I believe this file is correct for free-air >values. U671at.160 has free-air values that do >not correspond to the values given for the >observed and theoretical gravity. RLarsen. > >Input was... >Converted to time format with year at start. > >02/11/86 KAYE DUA0:[DATA.U671AT.N]U671AT.050; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 > >time, lat, long, time(sec) to nearest nav fix, data values Person who carried out this activity:
    U.S. Geological Survey (USGS) , Coastal and Marine Geology (CMG)
    Attn: Carolyn H. Degnan
    Geophysicist
    USGS Pacific Coastal & Marine Science Center, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7452 (voice)
    (831) 427-4748 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 20-Jun-2012 (process 3 of 7)
    Magnetics Data >06/20/2012 carolyn u-6-71-at.220_050 > >Reprocessed using subroutines from Susan Macmillan's >IGRF SYNTHESIS PROGRAM http://www.ngdc.noaa.gov/IAGA/vmod/igrf11.f >with IGRF-11 coeffiecients integrated into the source code. >/infobank/programs/mag/magred11/magred11.for >Using geodetic coordinate system (Earth shape approximated by spheriod) >with altitude 0.0 km (for sea level). > >Input was... >10/31/1998 /tiger/u/u671at/mag/u-6-71-at.200_050 >/bear/programs/edit/automerge/automerge > >Converted to time format with year at start. > >03/10/86 CAROLYN DRS$DATA:[U671AT.M]U671AT.200; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 >was U671AT.220 from 71BKUP > >03/22/85 CAROLYN USR$DISK:[DRS.DATA.U6.M]U671AT.220; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;3 > >Converted to time format with year at start. > >02/11/86 KAYE DUA0:[DATA.U671AT.N]U671AT.050; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 > >time, lat, long, time(sec) to nearest nav fix, data values Person who carried out this activity:
    U.S. Geological Survey (USGS) , Coastal and Marine Geology (CMG)
    Attn: Carolyn H. Degnan
    Geophysicist
    USGS Pacific Coastal & Marine Science Center, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7452 (voice)
    (831) 427-4748 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 31-Oct-1998 (process 4 of 7)
    Bathymetry Data >10/31/1998 /tiger/u/u671at/bath/u-6-71-at.325_050 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >03/07/86 BECKIE DUA0:[DATA.U671AT]U671AT.325; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 > >Input was... >Converted to time format with year at start. > >02/11/86 KAYE DUA0:[DATA.U671AT.N]U671AT.050; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 > >time, lat, long, time(sec) to nearest nav fix, data values Person who carried out this activity:
    U.S. Geological Survey (USGS) , Coastal and Marine Geology (CMG)
    Attn: Carolyn H. Degnan
    Geophysicist
    USGS Pacific Coastal & Marine Science Center, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7452 (voice)
    (831) 427-4748 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 20-Jun-2012 (process 5 of 7)
    MGD77 file creation - The available data for each cruise leg are re-formatted and combined into the Marine Geophysical Data Exchange Format (MGD77) and into the internal NGDC SEIS-NAV format by USGS using several USGS developed FORTRAN programs.The FORTRAN programs sample the navigation to every integer minute of the cruise. When necessary, the latitudes and longitudes are linearly interpolated. If the time between the actual navigation fixes exceeds five minutes, no data are included in the MGD77 file.To build the MGD77 file, gravity, magnetics, and bathymetry are added to this sampled navigation. When necessary, gravity, magnetics, and bathymetry data are linearly interpolated if the time between the actual data samples does not exceed five minutes. If a time gap exceeds this, the data are not reported.The navigation data are merged with the seismic shot point data in a SEIS- NAV format file. For this file, navigation data are interpolated for each shot point. Both types of files are written to magnetic tape and sent to NGDC. Person who carried out this activity:
    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
    Attn: Carolyn H. Degnan
    Geophysicist
    USGS Pacific Coastal & Marine Science Center, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7452 (voice)
    (831) 427-4748 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 01-Feb-2017 (process 6 of 7)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    aallwardt@usgs.gov
    Date: 19-Oct-2020 (process 7 of 7)
    Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?
    Hittelman, Allen M., Groman, Robert C., Haworth, Richard T., Holcombe, Troy L., McHendrie, Graig, Smith, Stuart M., and Metzger, Dan R., 2010, The marine geophysical data exchange format - MGD77 / MGD77T: National Geophysical Data Center, National Oceanic and Atmospheric Administration, Boulder, CO.

    Online Links:

    Other_Citation_Details: 25 p.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    The validity or accuracy of bathymetry and navigation data is highly qualitative and depends on equipment and operating condition variables. Data quality is unknown, MGD77T files were formatted from InfoBank files identified as best available version.
  2. How accurate are the geographic locations?
    Unspecified
  3. How accurate are the heights or depths?
    Unspecified
  4. Where are the gaps in the data? What is missing?
    Start and end date/times of data >Navigation Data (u-6-71-at.050 [SINS]) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >197111241740000 197112022111360 >197112022121480 197112022130000 >197112022141060 197112022141060 >197112022151180 197112022201300 >197112022211420 197112022211420 >197112022230000 197112022231000 >197112022241120 197112022241120 >197112022251300 197112022301360 >197112022311480 197112022331120 >197112022351360 197112030000000 >197112030011000 197112030011000 >197112030021060 197112030031180 >197112030041300 197112030041300 >197112030051420 197112030100000 >197112030111060 197112030111060 >197112030121180 197112030131300 >197112030141420 197112030141420 >197112030151540 197112030201060 >197112030211180 197112030211180 >197112030221360 197112030241000 >197112030251180 197112030301300 >197112030311480 197112030331120 >197112030341300 197112030341300 >197112030351420 197112030400000 >197112030411060 197112030411060 >197112030421240 197112030431360 >197112030441480 197112030501120 >197112030511240 197112030511240 >197112030521360 197112030541000 >197112030551180 197112030601300 >197112030611480 197112030631120 >197112030641240 197112030641240 >197112030651360 197112030711000 >197112030721060 197112030731180 >197112030741300 197112030741300 >197112030751420 197112030800000 >197112030811060 197112030811060 >197112030821180 197112030831300 >197112030841420 197112030841420 >197112030851540 197112030901000 >197112030911120 197112030911120 >197112030921240 197112030931360 >197112030941480 197112031001060 >197112031011180 197112031011180 >197112031021360 197112031041000 >197112031051180 197112051730000 >197112051800000 197112061000000 >197112061010060 197112061010060 >197112061020180 197112071210420 >197112071220480 197112091950360 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Gravity Data (u-6-71-at.161_050) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >197111241740000 197111252200000 >197111252215000 197111260710000 >197111260720000 197111262145000 >197111262205000 197111272150000 >197111272300000 197111282145000 >197111282215000 197111290010000 >197111290020000 197111300625000 >197111300635000 197111301850000 >197111301915000 197111301920000 >197111301950000 197111302005000 >197111302025000 197111302045000 >197111302100000 197112010140000 >197112010200000 197112021025000 >197112021035000 197112021250000 >197112021300000 197112021715000 >197112031100000 197112040325000 >197112040345000 197112040350000 >197112040400000 197112041545000 >197112041555000 197112050250000 >197112050300000 197112051725000 >197112051800000 197112060945000 >197112061030000 197112061515000 >197112061525000 197112070310000 >197112070320000 197112070625000 >197112070640000 197112071200000 >197112071230000 197112082030000 >197112082040000 197112091950000 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Magnetics Data (u-6-71-at.220_050) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >197111241801060 197111280411180 >197111280431480 197111280711060 >197111280731300 197111300720060 >197111300740300 197111302350120 >197112010010300 197112021801060 >197112021821540 197112022331120 >197112022351360 197112051630120 >197112051910120 197112091950360 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Bathymetry Data (u-6-71-at.325_050) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >197111241740000 197111250405000 >197111250525000 197111280230000 >197111280240000 197112021030000 >197112021300000 197112021730000 >197112031100000 197112032120000 >197112032130000 197112040505000 >197112040520000 197112040710000 >197112040716000 197112041220000 >197112041230000 197112041930000 >197112041950000 197112070945000 >197112071005000 197112080525000 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST
  5. How consistent are the relationships among the observations, including topology?
    This data set is from one field activity with unknown instrument calibrations. Processed bathymetric depths were spot checked based on latitude and longitude against the Global Multi-Resolution Topography (GMRT) grid within GeoMapApp to ensure reasonable values.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None. These data are held in the public domain.
Use_Constraints:
This information is not intended for navigational purposes. Read and fully comprehend the metadata prior to data use. Uses of these data should not violate the spatial resolution of the data. Where these data are used in combination with other data of different resolution, the resolution of the combined output will be limited by the lowest resolution of all the data. Acknowledge the U.S. Geological Survey in products derived from these data. Share data products developed using these data with the U.S. Geological Survey.This database has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.Although this Federal Geographic Data Committee-compliant metadata file is intended to document these data in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)
  2. What's the catalog number I need to order this data set? Downloadable Data
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 19-Oct-2020
Metadata author:
Gregory K. Miller
U.S. Geological Survey
Physical Scientist
U.S. Geological Survey, 600 Fourth Street South
St. Petersburg, FL
USA

(727) 803-8747, ext. 3020 (voice)
gmiller@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/SeriesReports/OFR/OFR_89-167/797.faq.html>
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