l876np.m77t - MGD77 data file for Geophysical data from field activity L-8-76-NP in Northern Pacific from 09/29/1976 to 10/21/1976

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Frequently anticipated questions:

What does this data set describe?

Title:
l876np.m77t - MGD77 data file for Geophysical data from field activity L-8-76-NP in Northern Pacific from 09/29/1976 to 10/21/1976
Abstract:
Single-beam bathymetry, magnetics, and gravity data along with transit satellite navigation data was collected as part of field activity L-8-76-NP in Northern Pacific from 09/29/1976 to 10/21/1976, http://walrus.wr.usgs.gov/infobank/l/l876np/html/l-8-76-np.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/l/l876np/html/l-8-76-np.bath.html http://walrus.wr.usgs.gov/infobank/l/l876np/html/l-8-76-np.grav.html http://walrus.wr.usgs.gov/infobank/l/l876np/html/l-8-76-np.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, l876np.m77t - MGD77 data file for Geophysical data from field activity L-8-76-NP in Northern Pacific from 09/29/1976 to 10/21/1976: 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: 169.61868
    East_Bounding_Coordinate: -159.74690
    North_Bounding_Coordinate: 52.06155
    South_Bounding_Coordinate: 21.90246
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 29-Sep-1976
    Ending_Date: 21-Oct-1976
    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: Northern Pacific
      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?
    l876np.m77t
    MGD77T single-beam bathymetry, gravity, and magnetics data file for l786np (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:19760929
    Maximum:19761021
    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:21.90246
    Maximum:52.06133
    Units:decimal degrees
    LON
    Longitude (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:-179.99933
    Maximum:179.9967
    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:0.04
    Maximum:9.74
    Units:seconds
    CORR_DEPTH
    Bathymetry, corrected depth (Source: U.S. Geological Survey)
    Range of values
    Minimum:30
    Maximum:7401
    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:63
    Maximum:63
    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:35222.6
    Maximum:52433
    Units:gammas
    MAG_TOT2
    Magnetics total field - 2nd sensor (Source: NGDC)
    Range of values
    Minimum:35924.6
    Maximum:58095
    Units:gammas
    MAG_RES
    Magnetics residual field field (Source: NGDC)
    Range of values
    Minimum:-1133.9
    Maximum:5637.9
    Units:gammas
    MAG_RESSEN
    SENSOR FOR RESIDUAL FIELD (Source: NGDC)
    Range of values
    Minimum:1
    Maximum:1
    Units:1 - first sensor, 2 - second sensor, 9 - Unspecified
    GRA_OBS
    Observed gravity (Source: NGDC)
    Range of values
    Minimum:978773.8
    Maximum:981041.3
    Units:milligals
    EOTVOS
    EOTVOS correction - E = 7.5 V cos(phi) * sin(alpha) + 0.0042 V*V (Source: NGDC)
    Range of values
    Minimum:-56.2
    Maximum:104.3
    Units:milligals
    FREEAIR
    Free-air Anomaly = G(observed) minus G(theoretical) (Source: NGDC)
    Range of values
    Minimum:-97.6
    Maximum:332.3
    Units:milligals
    Entity_and_Attribute_Overview:
    Bathymetry, magnetic, gravity, and navigation data for U.S. Geological Survey survey l786np in MGD77T format.
    Entity_and_Attribute_Detail_Citation:
    Attributes are obtained from MGD77T data files created from the navigation, gravity, magnetics 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?
    Brent Dalrymple(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: 30-Oct-2000 (process 1 of 7)
    Navigation Data >Converted to time format with year at start. > >01/31/86 KAYE DUA0:[DATA.L876NP.N]L876NP.011; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 > Person who carried out this activity:
    U.S. Geological Survey (USGS) , Coastal and Marine Geology (CMG)
    Attn: Clint Steele
    InfoBank Group Leader
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA
    USA

    (650) 329-5055 (voice)
    (650) 329-5190 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 31-Oct-1998 (process 2 of 7)
    Gravity Data >10/31/1998 /tiger/l/l876np/grav/l-8-76-np.160_011 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >02/04/86 BARB DUA0:[DATA.L876NP.G]L876NP.160; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 > >Input was... >Converted to time format with year at start. > >01/31/86 KAYE DUA0:[DATA.L876NP.N]L876NP.011; >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: Clint Steele
    InfoBank Group Leader
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA
    USA

    (650) 329-5055 (voice)
    (650) 329-5190 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 21-Jun-2012 (process 3 of 7)
    Magnetics Data >06/21/2012 carolyn l-8-76-np.260_011 > >Reprocessed using subroutines from Susan Macmillan's >IGRF SYNTHESIS PROGRAM >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/l/l876np/mag/l-8-76-np.240_011 >/bear/programs/edit/automerge/automerge > >Converted to time format with year at start. > >01/03/86 CAROLYN DRS$DATA:[L876NP.M]L876NP.240; >DRB0:[DRS.REFMT]REFORMAT.EXE;5 >272/0500 to 275/1900 (20 sec data) from > L876NP.200 from Barb >278/0500 to 295/0400 ( 5 min data) from > L876NP._.MAGSX1 on TAM139 > L876NP200.DAT on VAM139 > >Converted to time format with year at start. > >01/31/86 KAYE DUA0:[DATA.L876NP.N]L876NP.011; >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: Clint Steele
    InfoBank Group Leader
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA
    USA

    (650) 329-5055 (voice)
    (650) 329-5190 (FAX)
    infobank@octopus.wr.usgs.gov
    Date: 20-Nov-2000 (process 4 of 7)
    Bathymetry Data >10/31/1998 /tiger/l/l876np/bath/l-8-76-np.335_011 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >05/20/86 BECKIE DUA0:[DATA.LEE76]TEST.335; >DUA0:[DATA.LEE76]TEMP.EXE; > >02/11/86 BECKIE DISK$USERDISK:[BECKIE.TEMP]L876NP.335; >DRB0:[DRS.BAT]BATRED.EXE;1 >This file was hand-digetized in 2-way traveltime(secs). >It was reduced using no Matthews correction and velocity >of sound assumed was 1500m/sec. > >Input was... >Converted to time format with year at start. > >01/31/86 KAYE DUA0:[DATA.L876NP.N]L876NP.011; >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: Clint Steele
    InfoBank Group Leader
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA
    USA

    (650) 329-5055 (voice)
    (650) 329-5190 (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 (l-8-76-np.011 [DRS]) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >197609290140000 197610070702000 >197610070804000 197610070804000 >197610070900000 197610072030000 >197610072316000 197610080056000 >197610080142000 197610080400000 >197610080446000 197610080630000 >197610080712000 197610090456000 >197610090642000 197610100922000 >197610101016000 197610111206000 >197610111254000 197610121942000 >197610160230000 197610160230000 >197610160356000 197610160502000 >197610160606000 197610170940000 >197610171022000 197610200114000 >197610200206000 197610200240000 >197610200322000 197610200448000 >197610200530000 197610201820000 >197610201904000 197610201944000 >197610202046000 197610210432000 >197610210526000 197610210526000 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Gravity Data (l-8-76-np.160_011) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >197610040543300 197610040928300 >197610041028300 197610052023300 >197610060928300 197610061138300 >197610061328300 197610061428300 >197610061503300 197610070133300 >197610070148300 197610070228300 >197610070238300 197610070953300 >197610071018300 197610071028300 >197610072058300 197610080103300 >197610080113300 197610081438300 >197610081448300 197610082238300 >197610090028300 197610090443300 >197610090458300 197610090653300 >197610090713300 197610120133300 >197610120903300 197610121433300 >197610121443300 197610121828300 >197610160258300 197610171713300 >197610172158300 197610200123300 >197610200143300 197610201938300 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Magnetics Data (l-8-76-np.260_011) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >197609290512100 197609290512300 >197609290548200 197609300959300 >197609301045100 197609301200500 >197610010041000 197610011435400 >197610011525300 197610011934000 >197610040500000 197610051725000 >197610082345000 197610121440000 >197610160255000 197610171430000 >197610172200000 197610181750000 >197610182115000 197610191810000 >197610191825000 197610191830000 >197610191845000 197610192300000 >197610200035000 197610201130000 >197610201140000 197610201530000 >197610201630000 197610210430000 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Bathymetry Data (l-8-76-np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
  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_89-167/1311.faq.html>
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