Multibeam Acoustic Backscatter of the Short Bank Region, Santa Monica Bay, California

Frequently-anticipated questions:

• What does this data set describe?
  1. How should 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 should this data set be cited?

   United States Geological Survey, Coastal and Marine Geology (CMG), Chief, 2004, Multibeam Acoustic Backscatter of the Short Bank Region, Santa Monica Bay, California.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -118.65038847

   East_Bounding_Coordinate: -118.48874155

   North_Bounding_Coordinate: 33.94368538

   South_Bounding_Coordinate: 33.82901158

3. What does it look like?

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

   Beginning_Date: 30-Sep-1996

   Ending_Date: 29-Oct-1996

   Currentness_Reference: ground condition

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

   Geospatial_Data_Presentation_Form: XYZ ASCII

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

   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 0.00008. Longitudes are given to the nearest 0.00008. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is WGS84.
      The ellipsoid used is WGS84.
      The semi-major axis of the ellipsoid used is 6378137.00 meters.
      The flattening of the ellipsoid used is 1/0.003352811.
      

7. How does the data set describe geographic features?

   Entity_and_Attribute_Overview:

   Sample of Backscatter XYZ ASCII file

    Longitude, Latitude, DN Value
   (decimal degree, decimal degree, DN value)
   -118.67421,33.63640,207.696
   -118.67413,33.63640,206.398
   -118.67405,33.63640,203.770
   -118.67398,33.63640,201.170
   -118.67390,33.63640,201.098
   -118.67382,33.63640,202.064
   -118.67374,33.63640,202.693
   -118.67367,33.63640,202.720
   -118.67444,33.63640,201.992
   

   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)
   • United States Geological Survey (USGS),

2. Who also contributed to the data set?

3. To whom should users address questions about the data?
   Peter Dartnell
   United States Geological Survey (USGS)
   Physical Scientist
   USGS, MailStop 999, 345 Middlefield Road
   Menlo Park, CA 94025-3561
   USA
   

   (650) 329-5460 (voice)
   (650) 329-5411 (FAX)
   pdartnell@usgs.gov
   

Why was the data set created?

These data are intended for science researchers, students, policy makers, and the general public. The data can be used with geographic information systems (GIS) or other software to display acoustic backscatter data of the Short Bank Region, Santa Monica Bay, California..

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-1996 (process 1 of 1)

   The multibeam bathymetry and acoustic backscatter data were collected along a continuous swath perpendicular to the direction of the ship using a Kongsberg Simrad EM1000 multibeam sonar system. The data were cleaned of bad navigation and depth readings and corrected for tides to mean lower low water datum. Acoustic backscatter strength was converted from decibels (dB) to a non-dimensional digital number (DN) using the conversion, "Absolute Value(2DN/dB)", where DN ranges from 0 to 255 and dB ranges from 0 to -127. The acoustic backscatter values were gridded into a common grid. The gridded data were converted to ArcInfo GRID format using ArcInfo's ASCIIGRID command.The GRID was converted to an XYZ ASCII file by using the GRIDPOINT, ADDXY, and Tables' UNLOAD commands.

   Person who carried out this activity:
   

   Peter Dartnell
   United States Geological Survey (USGS)
   Physical Scientist
   USGS, MailStop 999, 345 Middlefield Road
   Menlo Park, CA 94025-3561
   USA
   

   (650) 329-5460 (voice)
   (650) 329-5411 (FAX)
   pdartnell@usgs.gov
   

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?

   Not determined.

2. How accurate are the geographic locations?

   0.5 meters

3. How accurate are the heights or depths?

   0.05 percent of the water depth. Depths corrected to mean lower low water datum.

4. Where are the gaps in the data? What is missing?

   Complete

5. How consistent are the relationships among the observations, including topology?

   Point features present.

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:

Please recognize the U.S. Geological Survey (USGS) as the source of this information. USGS-authored or produced data and information are in the public domain.

1. Who distributes the data set? (Distributor 1 of 1)
   United States Geological Survey (USGS)
   345 Middlefield Rd., MS-999
   Menlo Park, CA 94025
   USA
   

   (650)329-5460 (voice)
   

2. What's the catalog number I need to order this data set?

   C-1-96-SC data set

3. What legal disclaimers am I supposed to read?

   These data not intended for navigational purposes.

   Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, these data and information are provided with the understanding that they are not guaranteed to be usable, timely, accurate, or complete. Users are cautioned to consider carefully the provisional nature of these data and information before using them for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences. Conclusions drawn from, or actions undertaken on the basis of, such data and information are the sole responsibility of the user.

   Neither the U.S. Government nor any agency thereof, 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 data, software, information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights.

   Trade, firm, or product names and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ASCII
     Network links:	none

   • Cost to order the data: None

Who wrote the metadata?

Dates:

Last modified: 16-Dec-2003

Metadata author:

Peter Dartnell
United States Geological Survey (USGS)
Physical Scientist
USGS, MailStop 999, 345 Middlefield Road
Menlo Park, CA 94025-3561
USA

(650) 329-5460 (voice)
(650) 329-5411 (FAX)
pdartnell@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata ("CSDGM version 2") (FGDC-STD-001-1998)