l383wf.m77t - MGD77 data file for Geophysical data from field activity L-3-83-WF in Juan de Fuca from 08/19/1983 to 09/01/1983

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Frequently anticipated questions:


What does this data set describe?

Title:
l383wf.m77t - MGD77 data file for Geophysical data from field activity L-3-83-WF in Juan de Fuca from 08/19/1983 to 09/01/1983
Abstract:
Single-beam bathymetry and gravity data along with DGPS navigation data was collected as part of field activity L-3-83-WF in Juan de Fuca from 08/19/1983 to 09/01/1983, http://walrus.wr.usgs.gov/infobank/l/l383wf/html/l-3-83-wf.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/l383wf/html/l-3-83-wf.bath.html and http://walrus.wr.usgs.gov/infobank/l/l383wf/html/l-3-83-wf.grav.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, l383wf.m77t - MGD77 data file for Geophysical data from field activity L-3-83-WF in Juan de Fuca from 08/19/1983 to 09/01/1983: 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: -130.54948
    East_Bounding_Coordinate: -122.45927
    North_Bounding_Coordinate: 48.45309
    South_Bounding_Coordinate: 37.79864
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 19-Aug-1983
    Ending_Date: 01-Sep-1983
    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: Juan de Fuca
      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?
    l383wf.m77t
    MGD77T single-beam bathymetry data file for L383WF (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:19830820
    Maximum:19830901
    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:37.79864
    Maximum:48.45309
    Units:decimal degrees
    LON
    Longitude (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:-130.54948
    Maximum:-122.45927
    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:4.747
    Maximum:5.876
    Units:seconds
    CORR_DEPTH
    Bathymetry, corrected depth (Source: U.S. Geological Survey)
    Range of values
    Minimum:3541.2
    Maximum:4401
    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
    Entity_and_Attribute_Overview:
    Bathymetry, gravity, and navigation data for U.S. Geological Survey bathymetry survey L383WF in MGD77T format.
    Entity_and_Attribute_Detail_Citation:
    Attributes are obtained from MGD77T data files created from the navigation, gravity, 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?
    Bill Normark (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: 19-Jan-1996 (process 1 of 5)
    Navigation Data >Converted to time format with year at start. > >05/01/85 KAYE USR$DISK:[DRS.DATA.L383WF.N]NEW.052; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 > 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 5)
    Gravity Data >10/31/1998 /tiger/l/l383wf/grav/l-3-83-wf.110_052 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >05/08/85 BARB USR$DISK:[DRS.DATA.L383WF.G]L383WF.110; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 > >Input was... >Converted to time format with year at start. > >05/01/85 KAYE USR$DISK:[DRS.DATA.L383WF.N]NEW.052; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 > >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 3 of 5)
    Bathymetry Data >10/31/1998 /tiger/l/l383wf/bath/l-3-83-wf.330_052 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >05/14/85 BECKIE USR$DISK:[DRS.DATA.L383WF.B]L383WF.330; >DRA1:[DRS.BAT]BATRED.EXE;1 >This file was originally hand-digetized in corrected meters. >The travel-time calculated will assume 1500M per second, which >may not reflect the travel time used when data was originally >digetized. > >Input was... >Converted to time format with year at start. > >05/01/85 KAYE USR$DISK:[DRS.DATA.L383WF.N]NEW.052; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 > >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 4 of 5)
    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 5 of 5)
    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
  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-3-83-wf.052 [SINS]) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >198308200443000 198308222044000 >198308231805180 198309011514000 >198309011520000 198309011520000 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Gravity Data (l-3-83-wf.110_052) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >198308200443200 198308201746390 >198308201935190 198308201944540 >198308202144140 198308202144330 >198308202207250 198308202250540 >198308210010520 198308220310390 >198308220316030 198308231142390 >198308302217090 198309011519500 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Bathymetry Data (l-3-83-wf.330_052) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >198308201459310 198308201501550 >198308201507170 198308201635260 >198308201700100 198308201734180 >198308201741180 198308201751470 >198308201805410 198308201805410 >198308201815020 198308201819020 >198308201828010 198308201828010 >198308201837540 198308201837540 >198308201851100 198308201851100 >198308201859580 198308201859580 >198308201909590 198308201932410 >198308201939540 198308202003020 >198308202015010 198308202015010 >198308202029580 198308202029580 >198308202039310 198308202039310 >198308202050490 198308202050490 >198308202058440 198308202250200 >198308202256280 198308202316280 >198308202321350 198308210051080 >198308210056460 198308210109050 >198308210115190 198308210132220 >198308210139010 198308210152080 >198308210157120 198308210200570 >198308210206030 198308210210030 >198308210224570 198308210228100 >198308210236250 198308210241200 >198308210246580 198308210249180 >198308210300560 198308210318220 >198308210329040 198308210330100 >198308210336460 198308210343040 >198308210349340 198308210408430 >198308210418220 198308210507290 >198308210515020 198308210535140 >198308210541280 198308210542440 >198308210549200 198308210610010 >198308210617140 198308210617140 >198308210622460 198308210625530 >198308210632460 198308210632460 >198308210640090 198308210645010 >198308210650080 198308210650080 >198308210656000 198308210656000 >198308210701070 198308210701070 >198308210707080 198308210707080 >198308210714580 198308210725450 >198308210731260 198308210731260 >198308210737150 198308210737150 >198308210745000 198308210753020 >198308210759170 198308210800560 >198308210806010 198308210816160 >198308210822290 198308210822290 >198308210832260 198308210907370 >198308210915020 198308210915020 >198308210929580 198308210929580 >198308210945030 198308210945030 >198308210953090 198308210954560 >198308211000010 198308211003490 >198308211013020 198308211015070 >198308211030010 198308211030010 >198308211040570 198308211040570 >198308211046560 198308211048080 >198308211054250 198308211115030 >198308211122000 198308211122000 >198308211128560 198308211137500 >198308211143140 198308211304240 >198308211313000 198308211313000 >198308211318500 198308211320160 >198308211330020 198308211334230 >198308211343020 198308211343020 >198308211348440 198308211348440 >198308211356050 198308211356050 >198308211403030 198308211403030 >198308211412200 198308211412200 >198308211421100 198308211421100 >198308211427270 198308211430000 >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: 01-Feb-2017
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/847.faq.html>
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