MGL1109centerdepth.shp: Multibeam bathymetry data collected by the U.S. Geological Survey in the Gulf of Alaska in 2011 during cruise MGL1109, along-track center-beam depths extracted from 100-meter gridded data in shapefile format, geographic coordinates

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Barth, Ginger, Baldwin, Wayne E., Reece, Robert S., Gulick, Sean S., Danforth, William W., and Wong, Florence L., 20220825, MGL1109centerdepth.shp: Multibeam bathymetry data collected by the U.S. Geological Survey in the Gulf of Alaska in 2011 during cruise MGL1109, along-track center-beam depths extracted from 100-meter gridded data in shapefile format, geographic coordinates: data release DOI: 10.5066/F7HM56HK, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

   Online Links:

   • https://doi.org/10.5066/F7HM56HK
   • https://www.sciencebase.gov/catalog/item/5605a22ae4b058f706e5152c

   This is part of the following larger work.
   Barth, Ginger, Baldwin, Wayne E., Reece, Robert S., Gulick, Sean S., Danforth, William W., and Wong, Florence L., 2022, Multibeam bathymetry and acoustic backscatter data from the Alaskan region, Extended Continental Shelf Project, 2011 field season: Gulf of Alaska and Bering Sea: data release DOI: 10.5066/F7HM56HK, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

   Online Links:

   • https://doi.org/10.5066/F7HM56HK

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -152.379177
   East_Bounding_Coordinate: -137.883352
   North_Bounding_Coordinate: 57.711567
   South_Bounding_Coordinate: 48.308887
   

3. What does it look like?

   https://www.sciencebase.gov/catalog/file/get/5605a22ae4b058f706e5152c?name=MGL1109bathy.JPG&allowOpen=true (JPEG)

   MGL1109 bathymetry, Gulf of Alaska

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 03-Jun-2011

   Ending_Date: 25-Jun-2011

   Currentness_Reference:

   publication date

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: vector digital data
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • point (1997840)
   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 0.0196893509. Longitudes are given to the nearest 0.0324373614. Latitude and longitude values are specified in Decimal seconds. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
      
7. How does the data set describe geographic features?

   Attribute Table

   Table containing attribute information associated with the data set. (Source: Producer defined)

   EAST

   x-coordinate, UTM Zone 6N (Source: Producer defined)

   Range of values
   Minimum:	169222.94
   Maximum:	1175654.93
   Units:	meters

   NORTH

   y-coordinate, UTM Zone 6N (Source: Producer defined)

   Range of values
   Minimum:	5390933.7
   Maximum:	6407818.35
   Units:	meters

   LON

   longitude (Source: Producer defined)

   Range of values
   Minimum:	-152.378794
   Maximum:	-137.883352
   Units:	degrees

   LAT

   latitude (Source: Producer defined)

   Range of values
   Minimum:	48.308887
   Maximum:	57.711015
   Units:	degrees

   UTC

   time UTC (Source: Producer defined) Time formatted as HH:MM:SS, where HH = hour (0-23), MM = minute (0-59), SS = second to 3 decimal places (0-59.999).

   YRJD

   year and day of the year (Source: Producer defined) Year and day of the year (1-365).

   FILE

   filename (Source: Producer defined) swath filename

   EM122depth

   depth (Source: Producer defined)

   Range of values
   Minimum:	-5380.43
   Maximum:	-51.4
   Units:	meters

   jd_hhmmss

   julian day and time for labels (Source: Producer defined) day and time for labels

   sequence

   sorted record sequence number (Source: Producer defined) record number

   Entity_and_Attribute_Overview:

   The entity and attribute information provided here describes the tabular data associated with the data set. Please review the detailed descriptions that are provided (the individual attribute descriptions) for information on the values that appear as fields/table entries of the data set.

   Entity_and_Attribute_Detail_Citation:

   The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Ginger Barth
   • Wayne E. Baldwin
   • Robert S. Reece
   • Sean S. Gulick
   • William W. Danforth
   • Florence L. Wong
2. Who also contributed to the data set?
3. To whom should users address questions about the data?
   U.S. Geological Survey, Pacific Coastal and Marine Science Center

   Attn: PCMSC Science Data Coordinator

   2885 Mission Street

   Santa Cruz, CA
   

   831-427-4747 (voice)

   pcmsc_data@usgs.gov

Why was the data set created?

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: Jun-2011 (process 1 of 8)

   Multibeam bathymetry and backscatter data were collected using a 12 kHz Kongsberg Simrad EM-122 multibeam echosounder and SIS (v3.8.2) acquisition software. The system consists of two hull-mounted transducer arrays, a transmit unit (150 deg. x 1 deg.) located along the ship centerline, and a receive unit (1 deg. x 30 deg.) that is abaft and oriented athwart-ships. The transducer pod is tilted 4 degrees towards the bow to reduce noise from cavitation and bubbles. The system forms a swath of 288 beams that produce an across-track profile of 432 soundings. The SIS software processes range/angle data from each ping during acquisition, merging position, inertial-motion, and sound-velocity data to derive a solution for vessel motion and raybending, and calculate sounding depths and positions. Sound velocity information entered into SIS was obtained from the Applied Micro Systems Micro SV mounted on the transducer pod and 52 XBT profiles. XBT profiles were extended to 12 km depth with data generated by the unix program 'mblevitus', a module of the multibeam processing package MB-System (Caress and Chayes, 2006). Average water column salinity of 34.4 ppt was determined by extrapolating data from XCDT casts. Multibeam data were collected nearly continuously throughout the cruise, effectively mapping the seafloor along the course of the ship's track. Beam angle was set at 70 on each side throughout the program and swath widths were generally between 3 and 4 times water depth. SIS logged bathymetry and backscatter solutions to the Simrad '.all' format for archival purposes.

   Date: May-2012 (process 2 of 8)

   CARIS processing for MGL1109: A new CARIS HIPS project (ver. 7.1) was created with projection information set to Universal Transverse Mercator (UTM) Zone 6N, WGS84. Each Simrad EM122 data file (*.all) was imported to the new CARIS project using the Import/Conversion Wizard. A 100 meter resolution Bathymetric and Statistical Error (BASE) Surface was created and new files were added to the surface each Julian day. With the addition of new files, the BASE surface was reviewed for any inconsistencies or data anomalies. Navigation was edited as needed using the navigation editor tool in CARIS. Filters were applied to each line including beam to beam slopes and across track angle. The CARIS "surface filter" was applied to the data using the two standard deviation option. Swath data were also edited manually to remove obviously outlying soundings. Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Wayne Baldwin

   Geologist

   384 Woods Hole Road

   Woods Hole, MA
   

   USA

   508-457-2226 (voice)

   wbaldwin@usgs.gov

   Date: May-2012 (process 3 of 8)

   The 100 meter CARIS HIPS BASE surface for MGL1109 was exported from CARIS as a Bathymetric Attributed Grid (BAG) file. The resulting BAG file was used to import the surface into IVS3D DMagic as gridded data, then the surface was saved as a Fledermaus Digital Terrain Model in the IVS3D SD format. Finally, the Fledermaus ArcGIS module was used to export the surface directly to an ESRI Binary Grid. Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Wayne Baldwin

   Geologist

   384 Woods Hole Road

   Woods Hole, MA
   

   USA

   (508) 457-2226 (voice)

   (508) 457-2310 (FAX)

   wbaldwin@usgs.gov

   Date: May-2012 (process 4 of 8)

   Navigation information (Easting,Northing,Longitude,Latitude,UTC Time,Year-Julian Day,SIS Filename) were extracted from the CARIS HIPS database utilizing a Perl script that ran the CARIS command 'printfnav' on all edited EM122 data files. Unix 'cat' was used to concatenate the output nav files to a single file, 'grep' was used to extract only soundings flagged as accepted, then an 'awk' filter was used to extract records with unique navigation fixes, one per second. The resultant text file was used to create an ArcGIS point feature class (ArcMap, create feature class from XY table). Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Wayne Baldwin

   Geologist

   384 Woods Hole Road

   Woods Hole, MA
   

   USA

   (508) 457-2226 (voice)

   wbaldwin@usgs.gov

   Date: May-2012 (process 5 of 8)

   Version 1 of metadata compiled by wbaldwain@usgs.gov

   Date: May-2012 (process 6 of 8)

   The navigation text file created in the previous step was used to create an ArcGIS point feature class (ArcMap, create feature class from XY table). The navigation point feature class and the ESRI binary grid 'MGL1109_bathy' were used as the point and raster inputs for the ArcGIS Spatial Analyst tool 'Extract values to points', with the interpolate values at point locations option selected. The resultant point shapefile containing "Easting, Northing, Longitude, Latitude, UTC Time, Year-Julian Day, SIS Filename, Depth (meters)" was exported to ASCII text. Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: Wayne Baldwin

   Geologist

   384 Woods Hole Road

   Woods Hole, MA
   

   USA

   (508) 457-2226 (voice)

   wbaldwin@usgs.gov

   Date: Nov-2014 (process 7 of 8)

   A trackline shapefile strung through the original centerdepth file (MGL1109_EM122centerdepth.txt) had a loop that was not present in the 1-minute shipboard navigation fixes. The original file appeared to have been sorted on the FILE attribute, which has Julian day and time embedded, but some entries did not match the YRJD and UTC attributes and were, consequently, not time sequential. The text file was converted to a point shapefile with a new attribute "jd_hhmmss" combining YRJD and UTC that was used to re-sort the centerdepth file. The "sequence" attribute is the record number after the re-sort. The shapefile attributes are EAST,NORTH,LON,LAT,UTC,YRJD,FILE,EM122depth,jd_hhmmss,sequence. (fwong@usgs.gov)

   Date: 18-Aug-2022 (process 8 of 8)

   Metadata was modified to bring up to current USGS PCMSC standards. Point of Contact and Metadata Contact information was updated. Keywords were added and refined. Cross Reference citation added. Details about different Network Resource Name links was given in the Access Instructions section. Minor typos were corrected. No data information was changed. Person who carried out this activity:
   

   Susan A Cochran

   U.S. Geological Survey, Pacific Coastal and Marine Science Center

   Geologist

   2885 Mission St.

   Santa Cruz, CA
   

   United States

   831-460-7545 (voice)

   scochran@usgs.gov

3. What similar or related data should the user be aware of?
   Caress, David W., and Chayes, Dale N., 2006, MB-System source code.

   Online Links:

   • https://www3.mbari.org/data/mbsystem/html/mbsystem_home.html

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

1. How well have the observations been checked?
   Kongsberg-Simrad EM122 Multibeam Echosounder was used with transmit (fore-aft) and receive (athwart ships) beam widths of 1 degree, with swaths of 3-4 times water depth in water depths between 50 and 6000 m. Depth accuracies not determined, however Kongsberg-Simrad state that the system is capable of depth accuracies approaching 0.2 percent of water depth.
2. How accurate are the geographic locations?
   Horizontal positioning of the vessel was determined using a Kongsberg Seapath 300 series integrated inertial motion and positioning system. Positioning is accurate to better than 5 meters (at 95 percent confidence) during all surveying. All positioning is referenced to the WGS84 Datum.
3. How accurate are the heights or depths?
   No attempt was made to determine the accuracy of the system although recorded depths are typically within +/-10 m of the center-beam multibeam sounding.
4. Where are the gaps in the data? What is missing?
   Raw EM122 Multibeam Echosounder data collected during OBS operations were not used in the generation of this gridded dataset because OBS instruments were deployed along transects coincident with previously surveyed ship track. Upon inspection in CARIS during post-processing it was deemed appropriate to exclude the redundant data from the gridding process.
5. How consistent are the relationships among the observations, including topology?
   No formal logical accuracy tests were conducted

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey - ScienceBase

   Denver Federal Center, Building 810, Mail Stop 302

   Denver, CO
   

   1-888-275-8747 (voice)

   sciencebase@usgs.gov
2. What's the catalog number I need to order this data set? These data are available in shapefile format, along with accessory files and CSDGM FGDC-compliant metadata.
3. What legal disclaimers am I supposed to read?
   Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:	shapefile Size: 100
     Network links:	https://www.sciencebase.gov/catalog/file/get/5605a22ae4b058f706e5152c https://www.sciencebase.gov/catalog/item/5605a22ae4b058f706e5152c https://doi.org/10.5066/F7HM56HK

   • Cost to order the data: None

Who wrote the metadata?

Dates:

Last modified: 25-Aug-2022

Metadata author:

U.S. Geological Survey, Pacific Coastal and Marine Science Center

Attn: PCMSC Science Data Coordinator

2885 Mission Street

Santa Cruz, CA

831-427-4747 (voice)

pcmsc_data@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)