4-m resolution bathymetric grid of Tomales Bay, California (TOMALESG)

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?

   Anima, Roberto J. , Chin, John L. , Finlayson, David P. , McGann, Mary L. , and Wong, Florence L. , 2007, 4-m resolution bathymetric grid of Tomales Bay, California (TOMALESG): USGS Open-File Report USGS OFR 2008-1237, U.S. Geological Survey, Menlo Park, California.

   Online Links:

   • <URL:https://pubs.usgs.gov/of/2008/1237/>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -122.98388487

   East_Bounding_Coordinate: -122.83886718

   North_Bounding_Coordinate: 38.23903649

   South_Bounding_Coordinate: 38.09620335

3. What does it look like?

   <https://pubs.usgs.gov/of/2008/1237/images/tomalesg.jpg> (gif or jpg)

   preview image of report

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

   Calendar_Date: 2006

   Currentness_Reference: Ground Condition

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

   Geospatial_Data_Presentation_Form: map

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 3959 x 3172, 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: -123.0

      Latitude_of_Projection_Origin: 0.0

      False_Easting: 500000

      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 4.0
      Ordinates (y-coordinates) are specified to the nearest 4.0
      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 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.
      

7. How does the data set describe geographic features?

   Entity_and_Attribute_Overview:

   
   TOMALESG.STA:
   
   COLUMN   ITEM NAME        WIDTH OUTPUT  TYPE N.DEC  ALTERNATE NAME
       1  MIN                    8    15     F      3
       9  MAX                    8    15     F      3
      17  MEAN                   8    15     F      3
      25  STDV                   8    15     F      3
   
    MIN             MAX            MEAN            STDV
    -19.150           0.668          -4.379           2.452
   
   

   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)
   • Roberto J. Anima
   • John L. Chin
   • David P. Finlayson
   • Mary L. McGann
   • Florence L. Wong

2. Who also contributed to the data set?

3. To whom should users address questions about the data?
   Florence L. Wong
   United States Geological Survey (USGS)
   Geologist, GIS Coordinator
   USGS, MailStop 999, 345 Middlefield Road
   Menlo Park, CA 94025-3561
   USA
   

   (650) 329-5327 (voice)
   (650) 329-5190 (FAX)
   fwong@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) software to display geologic and oceanographic information.

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 4)

   Swath bathymetry. Swath bathymetry for the northern and central portions of Tamales Bay (cruise F-1-04-TB and F-2-05-TB) were collected using a pole-mounted, SEA Inc., 234 kHz, SWATHplus interferometric sidescan sonar system. Attitude compensation and vessel positioning were provided by a CodaOctopus F180 attitude and positioning system. Sound velocity profile measurements were collected with an Applied Micro Systems, SvPlus 3472.

   The horizontal datum of the surveys was established by differential GPS using the WGS84 ellipsoid. The vertical datum of the surveys was based on Mean Lower Low Water (MLLW) predictions for Marshall, Tomales Bay, using the software Tides and Currents by Nobeltec.

   Raw bathymetry and amplitude data were collected using the Swath Processor software provided with the sonar system and gridded at 1 m resolution using the accompanying Grid Processor software package. These raster data were then exported to Fledermaus, edited and smoothed in that package and finally exported to ESRI ASCII Grid format using USGS in-house software.

   Date: 2006 (process 2 of 4)

   Single-Beam Bathymetry. Single-beam echo sounder data were collected over the shallow tidelands of southern Tomales Bay during August 2006 (cruise B-1-06-TB). A pole-mounted ESE50 Echo sounder with a co-located Real-time kinematic (RTK) GPS receiver system provided real-time vertical and horizontal positioning of the sonar transducer during operations. These data were reduced to positional soundings on the sea floor using HYPACK (version 6.2) with a 30-second averaging period (to remove heave), gridded into a 10-m resolution DEM using Surfer version 8.0, and exported to ESRI ASCII Grid format using USGS in-house software.

   The horizontal and vertical datum of the survey was established by the RTK GPS system as WGS84 and NAVD88, respectively. The error ellipse on the location of the GPS receivers is typically < 5 cm and this propagates through to the sea floor with RMS errors on sea bed elevation of < 10 cm.

   Date: 2006 (process 3 of 4)

   4 m composite bathymetry. Each of the three surveys was resampled to a 4 m cell spacing using the Spline Smooth tool of Surfer 8. The swath bathymetry was converted from MLLW to NAVD88 vertical datum using VDatum (NOAA Office of the Coast Survey and National Geodetic Survey), and then the three surveys were blended together in ArcGIS using the MOSAIC TO NEW RASTER tool with the blend option. The final data set was trimmed to the convex hull of the survey data area.

   Date: 19-Sep-2007 (process 4 of 4)

   First draft of metadata created by florence using FGDCMETA.AML ver. 1.35 08/02/2000 on ArcInfo data set /we6/florence/cordell/tomales/covs/tomalesg

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?

   The advertised accuracy of the SWATHplus system in shallow waters is better than IHO S44 Special Order, but a total propagation error model has not been developed for the USGS system used in these surveys so the true error in both position and elevation is unknown. Furthermore, no operational tide measurements were available for the survey so there is likely to be a spatially and temporally variable vertical error due to differences between the predicted tides and the water levels actually experienced during the survey. Finally, a comparison of grid elevations having overlapping coverage between the 2004 and 2005 surveys revealed a 1.44 m vertical offset (median of all overlapping cells). This error may be due to a mis-configuration of the F180 unit, but the exact cause of the error is unknown. In the final DEM, a static offset of +1.44 m was added to the 2004 data to minimize the vertical offset between the 2004 and 2005 data. No additional vertical error analysis has been performed on these data.

2. How accurate are the geographic locations?

   See Attribute_Accuracy_Report.

3. How accurate are the heights or depths?

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

   See Attribute_Accuracy_Report.

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

   Not applicable for raster data.

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: These data are not to be used for navigation.

1. Who distributes the data set? (Distributor 1 of 1)
   United States Geological Survey (USGS)
   c/o Florence L. Wong
   Geologist, GIS Coordinator
   USGS, MailStop 999, 345 Middlefield Road
   Menlo Park, CA 94025-3561
   USA
   

   (650) 329-5327 (voice)
   (650) 329-5190 (FAX)
   fwong@usgs.gov
   

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

   USGS OFR 2007-xxx

3. What legal disclaimers am I supposed to read?

   Please recognize the U.S. Geological Survey (USGS) as the source of this information.

   Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data.

   The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.

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

     Data format:	Compressed file including Arcinfo grid and metadata. (version 9.2) Arcinfo ASCII grid Size: 5 MB
     Network links:	<https://pubs.usgs.gov/of/2008/1237/>

   • Cost to order the data: none

Who wrote the metadata?

Dates:

Last modified: 19-Sep-2007
Last Reviewed: Oct-2007

Metadata author:

United States Geological Survey (USGS)
c/o Florence L. Wong
Geologist, GIS Coordinator
USGS, MailStop 999, 345 Middlefield Road
Menlo Park, CA 94025-3561
USA

(650) 329-5327 (voice)
(650) 329-5190 (FAX)
fwong@usgs.gov

Metadata standard:

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