l3a81nc.m77t - MGD77 data file for Geophysical data from field activity L-3A-81-NC in Central Coast, Northern California from 04/16/1981 to 04/26/1981

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Frequently anticipated questions:


What does this data set describe?

Title:
l3a81nc.m77t - MGD77 data file for Geophysical data from field activity L-3A-81-NC in Central Coast, Northern California from 04/16/1981 to 04/26/1981
Abstract:
Single-beam bathymetry, gravity, and magnetic data along with DGPS navigation data was collected as part of field activity L-3A-81-NC in Central Coast, Northern California from 04/16/1981 to 04/26/1981, http://walrus.wr.usgs.gov/infobank/l/l3a81nc/html/l-3a-81-nc.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/l3a81nc/html/l-3a-81-nc.bath.html, http://walrus.wr.usgs.gov/infobank/l/l3a81nc/html/l-3a-81-nc.grav.html, and http://walrus.wr.usgs.gov/infobank/l/l3a81nc/html/l-3a-81-nc.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, l3a81nc.m77t - MGD77 data file for Geophysical data from field activity L-3A-81-NC in Central Coast, Northern California from 04/16/1981 to 04/26/1981: 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: -122.64710
    East_Bounding_Coordinate: -119.20955
    North_Bounding_Coordinate: 37.81914
    South_Bounding_Coordinate: 34.08567
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 16-Apr-1981
    Ending_Date: 26-Apr-1981
    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: Central Coast, Northern California
      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?
    l3a81nc.m77t
    MGD77T single-beam bathymetry, gravity, and magnetics data file for L3A81NC (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:19810416
    Maximum:19810426
    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:34.08567
    Maximum:37.81914
    Units:decimal degrees
    LON
    Longitude (Source: World Geodetic System 1984 Geographic Coordinate System)
    Range of values
    Minimum:-122.64710
    Maximum:-119.20955
    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
    MAG_TOT
    Magnetics total field - 1st sensor (Source: NGDC)
    Range of values
    Minimum:47488.5
    Maximum:59535
    Units:gammas
    MAG_RES
    Magnetics residual field field (Source: NGDC)
    Range of values
    Minimum:--2668.1
    Maximum:9798.5
    Units:gammas
    GRA_OBS
    Observed gravity (Source: NGDC)
    Range of values
    Minimum:979668.2
    Maximum:979967.7
    Units:milligals
    EOTVOS
    EOTVOS correction - E = 7.5 V cos(phi) * sin(alpha) + 0.0042 V*V (Source: NGDC)
    Range of values
    Minimum:-68.3
    Maximum:40.9
    Units:milligals
    FREEAIR
    Free-air Anomaly = G(observed) minus G(theoretical) (Source: NGDC)
    Range of values
    Minimum:-75.5
    Maximum:37.3
    Units:milligals
    Entity_and_Attribute_Overview:
    Bathymetry, gravity, magnetic, and navigation data for U.S. Geological Survey bathymetry survey L3A81NC in MGD77T format.
    Entity_and_Attribute_Detail_Citation:
    Attributes are obtained from MGD77T data files created from the navigation gravity, magnetic, 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?
    Dave McCulloch (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 6)
    Navigation Data >Converted to time format with year at start. > >05/09/85 KAYE USR$DISK:[KAYE.COASTAL]NEW.070; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 >Original filename is l381nc.sinsd1._ from VAM339 > 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 6)
    Gravity Data >10/31/1998 /tiger/l/l3a81nc/grav/l-3a-81-nc.152_070 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >10/11/85 BARB DRS$DATA:[L381NC.G]L381NC.152; >DRB0:[DRS.REFMT]REFORMAT.EXE;4 > >Input was... >Converted to time format with year at start. > >05/09/85 KAYE USR$DISK:[KAYE.COASTAL]NEW.070; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 >Original filename is l381nc.sinsd1._ from VAM339 > >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 6)
    Magnetics Data >06/20/2012 carolyn l-3a-81-nc.220_070 > >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/l/l3a81nc/mag/l-3a-81-nc.200_070 >/bear/programs/edit/automerge/automerge > >Converted to time format with year at start. > >11/18/85 CAROLYN DRS$DATA:[L381NC.M]L381NC.200; >DRB0:[DRS.REFMT]REFORMAT.EXE;4 >was L381NC._.MAGSB1 on TAM262 >was L381NC220.DAT on VAM262 > >Converted to time format with year at start. > >05/09/85 KAYE USR$DISK:[KAYE.COASTAL]NEW.070; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 >Original filename is l381nc.sinsd1._ from VAM339 > >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 6)
    Bathymetry Data >10/31/1998 /tiger/l/l3a81nc/bath/l-3a-81-nc.301_070 >/bear/programs/edit/automerge/automerge > >Input was... >Converted to time format with year at start. > >08/29/85 BECKIE DUA0:[DATA.L381NC.B]L381NC.301; >DRB0:[DRS.REFMT]REFORMAT.EXE;4 >This file is edited 2 min. digitrack bathy. > >Input was... >Converted to time format with year at start. > >05/09/85 KAYE USR$DISK:[KAYE.COASTAL]NEW.070; >USR$DISK:[DRS.REFMT]REFORMAT.EXE;4 >Original filename is l381nc.sinsd1._ from VAM339 > >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 6)
    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 6)
    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-3a-81-nc.070) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >198104161750000 198104181441000 >198104181459000 198104181525000 >198104181534000 198104240721000 >198104240737000 198104261705000 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Gravity Data (l-3a-81-nc.152_070) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >198104161900180 198104170014180 >198104170225180 198104170625180 >198104170640420 198104170836420 >198104170847420 198104171729420 >198104171740420 198104171832420 >198104171848420 198104180300420 >198104180315420 198104180720480 >198104181250180 198104181932420 >198104181939360 198104182011360 >198104182024360 198104182040360 >198104182051360 198104190227360 >198104190233180 198104190437540 >198104190446540 198104190507000 >198104190517000 198104190525000 >198104190602300 198104191328360 >198104191421360 198104191759240 >198104191808060 198104192215060 >198104192249300 198104200607480 >198104200626420 198104200646540 >198104200653000 198104200830240 >198104200837000 198104201453420 >198104201504420 198104201520420 >198104201529480 198104201824300 >198104201848480 198104202241120 >198104202321120 198104210659240 >198104210707240 198104210741240 >198104210751240 198104210809300 >198104210821300 198104211427360 >198104211446540 198104211549000 >198104211607000 198104211621000 >198104211631000 198104220058120 >198104220115120 198104220159180 >198104220221180 198104220249180 >198104220302360 198104220534480 >198104220542300 198104221029240 >198104221101240 198104221327540 >198104221336120 198104221915480 >198104221951480 198104222028000 >198104222039180 198104222045180 >198104222050300 198104230406480 >198104230420480 198104230436480 >198104230441540 198104230449540 >198104230504120 198104231005240 >198104231021240 198104231055300 >198104231111300 198104231223480 >198104231239480 198104231257540 >198104231335060 198104232029360 >198104232037360 198104240441240 >198104240517000 198104241041300 >198104241046360 198104241141360 >198104241216360 198104241642240 >198104241713240 198104241825240 >198104241832060 198104250321180 >198104250346180 198104250558480 >198104250613480 198104251641240 >198104251647540 198104251742000 >198104251751000 198104251815000 >198104251825180 198104251920300 >198104260350300 198104260645180 >198104260657180 198104260837180 >198104260856180 198104261258180 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Magnetics Data (l-3a-81-nc.220_070) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >198104171906400 198104180726430 >198104181242150 198104181939230 >198104181944350 198104190531100 >198104190607270 198104191804590 >198104191812030 198104200835350 >198104200841030 198104201830020 >198104201852500 198104210705580 >198104210712260 198104211433180 >198104211450540 198104220539580 >198104220546300 198104221334220 >198104221341100 198104231229340 >198104231243500 198104241831580 >198104241837060 198104251821300 >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >Bathymetry Data (l-3a-81-nc.301_070) >YYYYMMDDHHMMSST YYYYMMDDHHMMSST >198104170639400 198104180725470 >198104181242150 198104181937390 >198104181944350 198104182018350 >198104182032350 198104190529230 >198104190607270 198104191803030 >198104191812030 198104200834230 >198104200841030 198104201828270 >198104201852500 198104202249100 >198104202301100 198104210705020 >198104210712260 198104211433140 >198104211450540 198104211600580 >198104211607580 198104211607580 >198104211613580 198104220539060 >198104220546300 198104221333140 >198104221341100 198104222049180 >198104222054300 198104230441300 >198104230446540 198104231228460 >198104231243500 198104241830260 >198104241837060 198104251646060 >198104251652540 198104251714540 >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/850.faq.html>
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