# BackscatterA [8101]--Offshore Pigeon Point, California

#### 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?

Title: BackscatterA [8101]--Offshore Pigeon Point, California
Abstract:
This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate grids depending on mapping system. This metadata file refers to the data included in "BackscatterA_8101_OffshorePigeonPoint.zip," which is accessible from https://doi.org/10.5066/F7513W80. These data accompany the pamphlet and map sheets of Cochrane, G.R., Watt, J.T., Dartnell, P., Greene, H.G., Erdey, M.D., Dieter, B.E., Golden, N.E., Johnson, S.Y., Endris, C.A., Hartwell, S.R., Kvitek, R.G., Davenport, C.W., Krigsman, L.M., Ritchie, A.C., Sliter, R.W., Finlayson, D.P., and Maier, K.L. (G.R. Cochrane and S.A. Cochran, eds.), 2015, California State Waters Map Series—Offshore of Pigeon Point, California: U.S. Geological Survey Open-File Report 2015–1232, pamphlet 40 p., 10 sheets, scale 1:24,000, https://doi.org/10.3133/ofr20151232.
The acoustic-backscatter map of the Offshore of Pigeon Point map area, California, was generated from backscatter data collected by California State University, Monterey Bay (CSUMB), by Fugro Pelagos, and by the U.S. Geological Survey (USGS). Mapping was completed between 2006 and 2009, using a combination of 400-kHz Reson 7125 (CSUMB) and 244-kHz Reson 8101 (FUGRO) multibeam echosounders, as well as a 234-kHz SWATHplus bathymetric sidescan-sonar system (USGS). These mapping missions combined to collect backscatter data from about the 10-m isobath to beyond the 3-nautical-mile limit of California's State Waters. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).
Supplemental_Information:
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.

1. How might this data set be cited?
   Bretz, Carrie K., Kvitek, Rikk G., Dartnell, Peter, and Erdey, Mercedes D., 2015, BackscatterA [8101]--Offshore Pigeon Point, California: Data Series DS 781, U.S. Geological Survey, Reston, VA.

   Online Links:

   - https://www.sciencebase.gov/catalog/item/55480a65e4b0a658d79557a7

   This is part of the following larger work.

   Golden, Nadine E., 2013, California State Waters Map Series Data Catalog: Data Series DS 781, U.S. Geological Survey, Reston, VA.

   Online Links:

   - https://pubs.usgs.gov/ds/781/
   - https://cmgds.marine.usgs.gov/data/csmp/OffshorePigeonPoint/data_catalog_OffshorePigeonPoint.html

2. What geographic area does the data set cover?
   West_Bounding_Coordinate: -122.49
   East_Bounding_Coordinate: -122.29
   North_Bounding_Coordinate: 37.23
   South_Bounding_Coordinate: 37.07
3. What does it look like?
   https://www.sciencebase.gov/catalog/file/get/5547e66ae4b0a658d79520c0?name=BackscatterA_8101_OffshorePigeonPoint.jpg&allowOpen=true (JPEG)
     Acoustic backscatter imagery of offshore Pigeon Point.
4. Does the data set describe conditions during a particular time period?
   Beginning_Date: 2006
   Ending_Date: 2009
   Currentness_Reference:
     ground condition
5. What is the general form of this data set?
   Geospatial_Data_Presentation_Form: GeoTiff
6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      - Dimensions 8890 x 8890 x 1, type Grid Cell
   2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 10
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.00000
      Latitude_of_Projection_Origin: 0.00000
      False_Easting: 500000.0
      False_Northing: 0.00
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 2.0
      Ordinates (y-coordinates) are specified to the nearest 2.0
      Planar coordinates are specified in Meters
      The horizontal datum used is WGS84.
      The ellipsoid used is WGS84.
      The semi-major axis of the ellipsoid used is 6378137.00.
      The flattening of the ellipsoid used is 1/298.257223563.
7. How does the data set describe geographic features?
   Value
     BackscatterA [8101] intensity value (Source: ESRI)
     Rowid
       Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
     VALUE
       Backscatter intensity values (Source: ESRI)

       Range of values
       Minimum: | 39.0
       Maximum: | 254.0
       Units: | Integers representing intensity values

     COUNT
       The number of pixels (2m x 2m size grid cell) represented in each intensity value (see Attribute: VALUE). (Source: ESRI)

       Range of values
       Minimum: | 530
       Maximum: | 365204
       Units: | Integers

     Entity_and_Attribute_Overview:
     The merged Reson 8101 acoustic-backscatter grid was originally archived as an ESRI grid with the following attributes:

         Cell size = 2.0
         Number of rows = 8885
         Number of columns = 8880

         Data type = floating point

         Boundary
         Xmin = 545630
         Xmax = 563390
         Ymin = 4103330
         Ymax = 4121100

         Statistics
         Minimum value = 39
         Maximum value = 254
         Mean = 123.38
         Standard deviation = 32.20

         Coordinate system description
         Projection  UTM
         Zone  10
         Datum  WGS84
         Units  meter

     Entity_and_Attribute_Detail_Citation: none

### Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   - Carrie K. Bretz
   - Rikk G. Kvitek
   - Peter Dartnell
   - Mercedes D. Erdey
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
   US

   831-427-4747 (voice)
   pcmsc_data@usgs.gov

### Why was the data set created?

> These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems or other software to identify seafloor features.

### 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: 2006 (process 1 of 7)
     During the mapping missions, an Applanix position and motion compensation system (POS/MV) was used to accurately position the vessel during data collection, and it also accounted for vessel motion such as heave, pitch, and roll (position accuracy, +/-2 m; pitch, roll, and heading accuracy, +/-0.02 degrees; heave accuracy, +/-5 percent, or 5 cm). KGPS altitude data (Fugro Pelagos, StarFix HP & XP units; CSUMB, NavCom 2050) were used to account for tide cycle fluctuations and sound velocity profiles were collected with an Applied Microsystems SVPlus sound velocimeter. Soundings were corrected for vessel motion using the Applanix POS/MV data, for variations in water-column sound velocity using the AM SVPlus data, and for variations in water height (tides) using vertical-position data from the KGPS receivers. Processing and mosaicking of Reson 8101 trace data were completed using GEOCODER Version 3.2 level 1 (created by Luciano Fonseca; Fugro Pelagos Modified Test Release 16). Within Geocoder, the backscatter intensities were radiometrically corrected (including despeckling and angle varying gain adjustments) and the position of each acoustic sample was geometrically corrected for slant-range and georeferenced to UTM Zone 10 N, WGS1984 datum. After the lines were imported, they were mosaicked into a 1m resolution image. Overlap between parallel lines was resolved using a priority table based on the distance of each sample from the ship track, with samples closest to- and furthest from- the ship track given the lowest priority. An anti-aliasing algorithm was also applied. Person who carried out this activity:
     Carrie Bretz
     Seafloor Mapping Lab, California State University Monterey Bay
     Projects Manager, GIS; Metadata Supervisor
     100 Campus Center, Bldg 13
     Seaside, CA
     USA

     (831) 582-4197 (voice)
     carrie_bretz@csumb.edu
   Date: 2014 (process 2 of 7)
     California Seafloor Mapping Project 1- and 2-m resolution backscatter imagery (CSMP survey blocks CC-09, CC-10, and CC-11) within this map were downloaded from California State University, Monterey Bay, Seafloor Mapping Lab (https://seafloor.otterlabs.org/SFMLwebDATA.htm) and converted to grids. Backscatter grids of similar mapping systems were merged in a GIS and clipped to the boundary of the map area. Grids from different mapping systems were not merged together due to different mapping frequencies and processing techniques. Person who carried out this activity:
     Pete Dartnell
     U.S. Geological Survey, Pacific Coastal and Marine Science Center
     Physical Scientist
     2885 Mission Street
     Santa Cruz, CA
     USA

     (831) 460-7415 (voice)
     pdartnell@usgs.gov
   Date: 05-Oct-2017 (process 3 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: 26-Apr-2018 (process 4 of 7)
     Added keywords from Coastal and Marine Ecological Classification Standard (CMECS) to metadata. 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: 22-Jun-2018 (process 5 of 7)
     Corrected author spelling in Larger Work section Person who carried out this activity:
     Susan A Cochran
     U.S. Geological Survey, Pacific Coastal and Marine Science Center
     Geologist
     2885 Mission Street
     Santa Cruz, CA
     USA

     (831) 460-7545 (voice)
     scochran@usgs.gov
   Date: 19-Oct-2020 (process 6 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
   Date: 01-Nov-2021 (process 7 of 7)
     Edits were made to bring the metadata up to current PCMSC standards including standardizing authors' names, adding a doi# link, correcting typos, refining keywords, and using current access and distribution liability statements. Point of Contact and Metadata Contact information sections were changed to static PCMSC contact information. No data were changed. The metadata available from a harvester may supersede metadata bundled within a download file. Users are advised to compare the metadata date of this file to any similar file to ensure they are using the most recent version. Person who carried out this activity:
     U.S. Geological Survey
     Attn: Susan A. Cochran
     Geologist
     2885 Mission Street
     Santa Cruz, CA

     831-460-7545 (voice)
     scochran@usgs.gov
3. What similar or related data should the user be aware of?
   Cochrane, Guy R., Watt, Janet T., Dartnell, Peter, Greene, H. Gary, Erdey, Mercedes D., Dieter, Bryan E., Golden, Nadine E., Johnson, Samuel Y., Endris, Charles A., Hartwell, Stephen R., Kvitek, Rikk G., Davenport, Clifton W., Krigsman, Lisa M., Ritchie, Andrew C., Sliter, Ray W., Finlayson, David P., and Maier, Katherine L., 2015, California State Waters Map Series--Offshore of Pigeon Point, California: Open-File Report 2015-1232, U.S. Geological Survey, Reston, VA.

   Online Links:

   - https://doi.org/10.3133/ofr20151232

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

1. How well have the observations been checked?
   Not applicable for raster data.
2. How accurate are the geographic locations?
   Estimated to be no less than 2 m, owing to water depth and total propagated uncertainties of the mapping systems, which include sonar system, position and motion compensation system, and navigation, as well as data processing that includes sounding cleaning, gridding, and datum transformations.
3. How accurate are the heights or depths?
   Not applicable to acoustic-backscatter imagery.
4. Where are the gaps in the data? What is missing?
   Complete
5. How consistent are the relationships among the observations, including topology?
   Unspecified

### How can someone get a copy of the data set?

> Are there legal restrictions on access or use of the data?

> > Access_Constraints: None
> > Use_Constraints:
> > USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey and California State University Monterey Bay as the originator(s) of the dataset and in products derived from these data.

1. Who distributes the data set? (Distributor 1 of 1)
   U.S. Geological Survey
   345 Middlefield Rd
   Menlo Park, CA
   USA

   (650) 329-4309 (voice)
2. What's the catalog number I need to order this data set? `The .zip file (BackscatterA_8101_OffshorePigeonPoint.zip) includes the .tfw, .tif, .tif.aux.xml, and .tif.ovr files, as well as FGDC-compliant metadata for the BackscatterA [8101] data layer in the Offshore Pigeon Point region of California.`
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: | The .zip file for the TIFF image includes the image (.tif), the world registration file (.tfw), and the text (.txt) and XML (.tif.xml) versions of the metadata for the BackscatterA [8101] data layer of Offshore Pigeon Point, California. in format TIFF (version ArcMap (version 10.0, ESRI , 2011)) Raster data layer is registered TIFF image in the UTM Zone 10 coordinate system with datum WGS84. Size: 22.4
     Network links: | https://www.sciencebase.gov/catalog/file/get/55480a65e4b0a658d79557a7 https://cmgds.marine.usgs.gov/data/csmp/OffshorePigeonPoint/data_catalog_OffshorePigeonPoint.html https://doi.org/10.3133/ds781

   - Cost to order the data: none

5. What hardware or software do I need in order to use the data set?

   > The downloadable data file has been compressed with the "zip" command and can be unzipped with Winzip (or other tool) on Windows systems. To utilize these data, the user must have software capable of uncompressing the WinZip file and importing and viewing an Esri ArcMap TIFF. Users should download the ArcGIS Project File, OffshorePigeonPointGIS.mxd.zip, a compressed (with the "zip" command) version of the ArcMap document (.mxd) that has all the data layers loaded in the table of contents for "Offshore Pigeon Point" and has all the data symbolized as on the data release map sheets. Download and save this ArcGIS project file, including all data layers, to the directory the user has created for this GIS.

### Who wrote the metadata?

Dates:
  Last modified: 01-Nov-2021
Metadata author:
  U.S. Geological Survey, Pacific Coastal and Marine Science Center
  Attn: PCMSC Science Data Coordinator
  2885 Mission Street
  Santa Cruz, CA
  US

  831-427-4747 (voice)
  pcmsc_data@usgs.gov
Metadata standard:
  Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

Generated by `mp` version 2.9.50 on Thu Nov 4 17:27:55 2021