IRIS Chirp Seismic-Reflection Profile JPEG Images Collected in Apalachicola Bay on U.S. Geological Survey Cruise 06001

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Frequently-anticipated questions:

What does this data set describe?

Title:
IRIS Chirp Seismic-Reflection Profile JPEG Images Collected in Apalachicola Bay on U.S. Geological Survey Cruise 06001
Abstract:
Apalachicola Bay and St. George Sound contain the largest oyster fishery in Florida, and the growth and distribution of the numerous oyster reefs here are the combined product of modern estuarine conditions and the late Holocene evolution of the bay. A suite of geophysical data and cores were collected during a cooperative study by the U.S. Geological Survey, the National Oceanic and Atmospheric Administration Coastal Services Center, and the Apalachicola National Estuarine Research Reserve to refine the geology of the bay floor as well as the bay's Holocene stratigraphy. Sidescan-sonar imagery, bathymetry, high-resolution seismic profiles, and cores show that oyster reefs occupy the crests of sandy shoals that range from 1 to 7 kilometers in length, while most of the remainder of the bay floor is covered by mud. The sandy shoals are the surficial expression of broader sand deposits associated with deltas that advanced southward into the bay between 6,400 and 4,400 years before present. The seismic and core data indicate that the extent of oyster reefs was greatest between 2,400 and 1,200 years before present and has decreased since then due to the continued input of mud to the bay by the Apalachicola River. The association of oyster reefs with the middle to late Holocene sandy delta deposits indicates that the present distribution of oyster beds is controlled in part by the geologic evolution of the estuary. For more information on the surveys involved in this project, see <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2005-001-FA> and <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2006-001-FA>.
  1. How should this data set be cited?

    Foster, David S. , and Cross, VeeAnn A. , 2012, IRIS Chirp Seismic-Reflection Profile JPEG Images Collected in Apalachicola Bay on U.S. Geological Survey Cruise 06001: Open-File Report 2012-1003, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Cross, V.A., Twichell, D.C., Foster, D.S., and O'Brien, T.F., 2012, Apalachicola Bay Interpreted Seismic Horizons and Updated IRIS Chirp Seismic-Reflection Data: Open-File Report 2012-1003, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -85.062710
    East_Bounding_Coordinate: -84.809553
    North_Bounding_Coordinate: 29.746692
    South_Bounding_Coordinate: 29.618457

  3. What does it look like?

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

    Beginning_Date: 03-Jun-2006
    Ending_Date: 27-Jun-2006
    Currentness_Reference: ground condition

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

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

    2. What coordinate system is used to 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? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    David C. Twichell
    U.S. Geological Survey
    Oceanographer
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2266 (voice)
    (508) 457-2310 (FAX)
    dtwichell@usgs.gov

Why was the data set created?

These images are provided as an archive of the IRIS seismic-reflection profile images collected on USGS Field Activity 2006-001-FA. These images generally correspond to the lines presented in the polyline shapefile asv_lines_Calibrated available from:<http://pubs.usgs.gov/of/2012/1003/html/catalog.html>. The polylines represent the lines used to load the data into seismic interpretation software so some of the lines are split in two parts. But the shot point navigation and linear referencing measurement (shots) do reflect the same information as the images.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    Source_Contribution:
    The data were collected using the USGS WHCMSC Autonomous Surface Vessel (ASV) IRIS. This system is designed to operate in shallow water (1-5 meters). IRIS is a catamaran platform 3 meters in length, 1.2 meters in width, and approximately 118 kilograms. The vehicle is operated remotely through a wireless modem network enabling real-time monitoring of data acquisition. The system is navigated using a ZXW RTK augmented GPS system enclosed on a platform in the middle of the catamaran. An enclosed onboard micro-processor-based motor controller provides signals for speed and steering to hull-mounted brushless direct-current thrusters. A center-mounted keel encloses the chirp dual-frequency (100/400 kHz model 4200 EdgeTech) sidescan-sonar transducers and EdgeTech 424 chirp seismic-reflection hydrophones. Mounted in the port hull are the EdgeTech 424 chirp seismic-reflection transducer and a single-beam 235 kHz echosounder. A Sony IP based wireless video camera is installed on the mast of IRIS for the purpose of obstacle avoidance. An onboard Fluxgate magnetometer provides heading, heave, pitch, and roll. IRIS is powered by 2-4 24-volt NiMH batteries located in each hull and has an approximate run-time of five hours at 4 knots.

  2. How were the data generated, processed, and modified?

    Date: 2006 (process 1 of 3)
    The seismic data were acquired with an EdgeTech SB-424 sub-bottom profiler and recorded in JSF format using JSTAR, EdgeTech's acquisition software. The research effort within Apalachicola Bay represented the first use of IRIS in full survey mode. As such, the system needed to be 'rung-out' during the first several days of surveying. A file naming convention developed over the first few days of surveying and acquisition settings (hardware and software) were modified several times until standardized settings could be established for Apalachicola Bay. Initial trouble-shooting dealt with several issues including a variation in the field in which navigation was stored within the JSF header and in the resolution of the navigation (seconds of arc vs. minutes of arc). Correcting these issues required re-running particular files though EdgeTech's DISCOVER software and saving new JSF files. Files that were saved through DISCOVER are signified by a 'yes' in the 'discover' field within the shapefile. A 'no' within the 'discover' field, indicates that the JSF file was correct in its original format; re-running through DISCOVER was not required. The JSF files were then converted to SEG-Y format using jsf2segy, a C-program written by Tom O'Brien at the Woods Hole, Science Center, U.S. Geological Survey. See the asv_lines_calibrated polyline shapefile available from <http://pubs.usgs.gov/of/2012/1003/html/catalog.html> to determine which files required re-running through EdgeTech's DISCOVER software.

    Person who carried out this activity:

    Tom O'Brien
    U.S. Geological Survey
    Marine Geophysical Systems Expert
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2246 (voice)
    5084572310 (FAX)
    tobrien@usgs.gov

    Date: 2006 (process 2 of 3)
    These original SEG-Y files are in IEEE format and were converted to IBM floating point using SIOSEIS. In addition to this conversion, the shot numbers have been renumbered in order to start at one.

    Person who carried out this activity:

    David S. Foster
    U.S. Geological Survey
    Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2271 (voice)
    (508) 457-2310 (FAX)
    dfoster@usgs.gov

    Date: 2006 (process 3 of 3)
    A csh script utilized Seismic Unix (v. 4.0) to generate JPEG images of each seismic profile.

    Person who carried out this activity:

    David S. Foster
    U.S. Geological Survey
    Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2271 (voice)
    (508) 457-2310 (FAX)
    dfoster@usgs.gov

  3. What similar or related data should the user be aware of?

    Twichell, D.C., Andrews, B.D., Edmiston, H.L., and Stevenson, W.R., 2007, Geophysical mapping of oyster habitats in a shallow estuary; Apalachicola Bay, Florida: Open-File Report 2006-1381, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    Twichell, D.C., Pendleton, E.A., Poore, R.Z., Osterman, L.E., and Kelso, K.W., 2009, Vibracore, radiocarbon, microfossil, and grain-size data from Apalachicola Bay, Florida: Open-File Report 2009-1031, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Bergeron, E., Worley, C.R., and O'Brien, T.F., 2007, Progress in the development of shallow-water mapping systems: using an autonomous surface vehicle for shallow-water geophysical studies: Sea Technology v. 48, no. 6, p. 10-15, Compass Publications, Inc., Arlington, VA.

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?

    IRIS was navigated with a Real-Time Kinematic (RTK) GPS, with the GPS antenna mounted directly over the seismic transducer. This system can provide positions to within 0.1 meters. However, due to some errors with the acquisition software, this accuracy is reduced. The accuracy is approximately 2 m given the constraints of the acquisition system.

  3. How accurate are the heights or depths?

    The transducers for the IRIS system are barely below the water surface - less than half a meter. This depth is not adjusted for during acquisition or processing.

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

    No data were acquired on the following dates: 6/8/2006, 6/10/2006 6/12/2006, 6/13/2006, 6/15/2006, 6/16/2006, 6/17/2006, 6/18/2006, 6/19/2006, 6/20/2006. These dates correspond to Julian days 159, 161, 163, 164, 166, 167, 168, 169, 170, and 171 respectively. In addition, lines for which no valid seismic data were available were deleted.

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

    Due to modifications to acquisition parameters during the initial days of surveying, the format in which navigation was stored in the SEG-Y headers varies: navigation is stored in either decimal arc seconds (0.01) or decimal arc minutes (0.0001). In order to properly extract and convert navigation to latitude/longitude divisors of 360000 and 600000 were used for decimal arc seconds and decimal arc minutes, respectively. Prior to JD172, the acquisition system did not consistently record longitude as a negative value (western hemisphere). Thus, either 600000 or -600000 was used to convert arc minutes to longitude based on whether the acquisition software recorded negative or positive longitude values. So although each line has a JPEG image, many lines had to be handled differently to acquire consistent results. Inconsistencies exist in the filenaming convention for individual seismic data collection lines. Because the filenames reflect the original data file names acquired in the field, they were left alone.

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:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the originators of this dataset.

  1. Who distributes the data set? (Distributor 1 of 1)

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov

  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?

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

    This WinZip file contains seismic-reflection profiles as JPEG images. The user must have software capable of uncompressing the WinZip file and display the JPEGs.

Who wrote the metadata?

Dates:
Last modified: 25-Jan-2012
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
Woods Hole Coastal and Marine Science Center
Woods Hole, MA 02543-1598

(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)
vatnipp@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.6 on Wed Apr 18 17:09:31 2012