ESRI Binary 75-m Grid of the Lowstand Surface in Apalachicola Bay based on Seismic-Reflection Profiles Collected in 2006 from U.S. Geological Survey Cruise 06001 (LOWFILCLIP, UTM, Zone 16, WGS84)

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Frequently anticipated questions:

What does this data set describe?

Title:
ESRI Binary 75-m Grid of the Lowstand Surface in Apalachicola Bay based on Seismic-Reflection Profiles Collected in 2006 from U.S. Geological Survey Cruise 06001 (LOWFILCLIP, UTM, Zone 16, WGS84)
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 might this data set be cited?
    Twichell, David C., and Cross, VeeAnn A., 2012, ESRI Binary 75-m Grid of the Lowstand Surface in Apalachicola Bay based on Seismic-Reflection Profiles Collected in 2006 from U.S. Geological Survey Cruise 06001 (LOWFILCLIP, UTM, Zone 16, WGS84): 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, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -85.049997
    East_Bounding_Coordinate: -84.875864
    North_Bounding_Coordinate: 29.722211
    South_Bounding_Coordinate: 29.611336
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 31-May-2006
    Ending_Date: 27-Jun-2006
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: raster digital data
  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 160 x 222 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: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 75.000000
      Ordinates (y-coordinates) are specified to the nearest 75.000000
      Planar coordinates are specified in meters
      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Mean lower low water
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Implicit coordinate
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    Depth values are recorded as negatives with more negative values indicating deeper water.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • David C. Twichell
    • VeeAnn A. Cross
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?

Why was the data set created?

This grid represents the interpretation of the lowstand surface based on seismic-reflection profiles collected in 2006 in Apalachicola Bay. This surface is an irregular erosional surface that was cut primarily by rivers during Pleistocene lowstands of sea level.

How was the data set created?

  1. From what previous works were the data drawn?
    none (source 1 of 1)
    U.S. Geological Survey, unpublished material, Data acquisition.

    Type_of_Source_Media: digital files
    Source_Contribution:
    The seismic data used for the interpretation come from two different seismic systems. The bulk of the data are from the EdgeTech FSSB 424 system pole mounted on the R/V Rafael. These data were logged in SEG-Y format using SBLogger. This system had a 1/4 second fire rate. The remainder of the data, in the shallower areas, were acquired with the USGS IRIS system. IRIS is a remotely operated vehicle that has an EdgeTtech FSSB 424 chirp sub-bottom profiling system mounted to it. The seismic data were recorded by JSTAR, a software package developed by EdgeTech. This system had a much faster fire rate, almost 15 times per second. The EdgeTech FSSB 424 is a chirp sub-bottom profiler that operates within a 4-24kHz frequency range. The IRIS vehicle is navigated using Real-Time Kinematic (RTK) GPS. The antenna is mounted directly on the platform to minimize navigational error. The R/V Rafael was also navigated with an RTK GPS system with the navigation antenna approximately 1.5 meters forward of the seismic transducer. This offset was not accounted for.
  2. How were the data generated, processed, and modified?
    Date: 2006 (process 1 of 14)
    Two different seismic systems acquired data in Apalachicola Bay in 2006. One system was the EdgeTech FSSB 424 (4-24kHz) aboard the R/V Rafael. These data were acquired as SEG-Y files using SBLogger. The second seismic system was also an EdgeTech FSSB 424 chirp system mounted on the USGS autonomous vehicle IRIS. These data were acquired with JSTAR in JSF format and converted to SEG-Y format using a C-program written by Tom O'Brien (USGS, Woods Hole). These SEG-Y files were then converted from IEEE format to IBM floating point using SIOSEIS, and the shots were renumbered starting at one. With initial preparation work on the seismic data complete, these data and navigation needed to be loaded into Landmark SeisWorks software for interpretation. In order to load the seismic data and navigation into Landmark SeisWorks software the navigation needed to be extracted from the header of the seismic data. An AWK script was used to extract the navigation from the seismic data headers and export in UTM, Zone 16 eastings and northings, rounded to the nearest meter. Person who carried out this activity:
    U.S. Geological Survey
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    Date: 2007 (process 2 of 14)
    Once the navigation is extracted from the seismic data, this navigation has to be loaded into the interpretation software. In this case, that's Landmark SeisWorks version R2003. The navigation is loaded using Data - Management - Seismic Data Manager. A new survey is created (06001 for the Rafael data, asv06 for the IRIS data). Then, Data - Import - Seismic Data Loader and point to the navigation text file. When loading the navigation, use a decimation of 0, use first shot point if duplicates are found, and overwrite data in target project if necessary. A decimation of zero was used because the IRIS navigation had already been decimated to take every 5th record from the complete navigation extracted from the headers of the IRIS seismics. The Rafael data did not need decimation. The Rafael data had a 1/4 second fire rate while the IRIS data fired at approximately 15 shots per second. Once the navigation is loaded and verified, then the actual seismic data can be loaded. To do this, use PostStack Data Loader. There was a small issue in working with seismic data in SeisWorks where it's better to have all the seismic profiles at the same sample rate. It's a display issue in the interpretation phase where opening a profile in a window with a different sample rate than the previously loaded profile doesn't always refresh the window properly. The result is an incorrect interpretation - the interpreted line falls in the wrong spot vertically. The seismic data were resampled to the same sample rate to eliminate this problem. The Rafael acquired data used two different sample rates: 40 microseconds and 80 microseconds. The Rafael seismics were all resampled to 40 microseconds in the PostStack data loader. Additionally, the lines had an automatic 8-bit scaling applied to each profile. The IRIS seismic lines were acquired with two sample rates - 23 microseconds and 46 microseconds. All of the lines were resampled to a 40 microsecond sampling interval in PostStack data loader and had an automatic 8-bit scaling applied to each profile. With the seismic data now loaded, the project has to be modified so these changes are reflected in the surveys and the data can be interpreted. Person who carried out this activity:
    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 2008 (process 3 of 14)
    The lowstand horizon was created in SeisWorks, and the lowstand surface was digitized from each seismic reflection profile where present. The surface is identified on seismic profiles as an irregular reflector that separates the underlying acoustically massive material from overlying acoustic units characterized by parallel, continuous closely spaced reflectors. Person who carried out this activity:
    David C. Twichell
    U.S. Geological Survey
    Oceanographer
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA

    (508) 548-8700 x2266 (voice)
    (508) 457-2310 (FAX)
    dtwichell@usgs.gov
    Date: 2008 (process 4 of 14)
    Once the interpretation is complete, the horizon is exported as a text file with the line name, easting, northing, and the depth to the horizon in milliseconds (two-way travel time). This process step and all subsequent process steps were overseen by the same person - VeeAnn A. Cross. Person who carried out this activity:
    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 2008 (process 5 of 14)
    A header line is added to the exported text file, and converted from a tab-delimited file to a comma-delimited file.
    Date: 2008 (process 6 of 14)
    ArcMap 9.2 was used to load this text file as an event theme using Tools - Add XY data. The projection is defined on input as UTM, Zone 16, WGS84.
    Date: 2008 (process 7 of 14)
    This event theme is converted to a shapefile by right mouse click - Data - Export Data and generating the output shapefile low021508csv.shp. This shapefile represents the depth to the lowstand horizon in milliseconds (two-way travel time). Any points falling outside Apalachicola Bay were deleted. The attribute mtrs_1800 was added and field calculator was used to convert the depth in milliseconds to depth in meters using 1800 meters per second and changing the sign so that more negative indicates deeper. This value does not take into account the difference of the speed of sound in water vs sediment. To account for a speed of sound difference in the water column and the sediment, this shapefile was joined with seafloor.shp and the output put to join_sf2low2.shp. The attribute ms_minus was added to this shapefile. Because of small gaps in interpreting the various surfaces, the records where the distance between joined values is less than 5 meters were selected. The joined seafloor ms are negatives, with the lowstand travel times positive, so ms_minus = ms (lowstand) + ms_2 (from seafloor) which yields the travel time in the sediment. Then the records selection was switched (large distances reflecting points joined more than 5 meters away) and the ms_minus was set to -9999.
    Date: 2008 (process 8 of 14)
    The isopach travel times where the lowstand surface exists were converted to meters in ArcMap 9.2 by using the attribute calculator and converting the travel time to meters using a speed of sound of 1800 meters per second. VAC Extras 2.02 gridspot tool was used to extract the sea floor depth in meters from the sea floor grid (topo2r_sf) and place in the attribute sf_grd. The grid was used instead of the interpreted sea floor values because the grid is primarily composed of the swath bathymetry values and using the interpolated grid will maintain surface relationships. A new attribute was added to the shapefile "low4grd" and the field calculator was used such that low4grd = sf_grd - lowiso_m. The sea floor grid values are negative while the lowiso_m are positive, therefore this calculation will give the total depth.
    Date: 2008 (process 9 of 14)
    The lowstand surface is an erosion surface that should follow drainage rules. Topo2Raster is a good gridding technique for these types of datasets. Additionally, the drainage enforcement is enhanced when stream thalwegs are included in the gridding process. These thalwegs can be inferred by studying the data points and creating a shapefile to reflect these locations. This information can then be supplied to the gridding algorithm. Using ArcMap 9.2 - ArcToolbox - Spatial Analyst Tools - Interpolation - Topo to Raster. Input features: joinsf2low2.shp attribute low4grd data type PointElevation. The boundary file was lowstand_outline_3.shp. lowstandthal_sm3 was used as a stream input. The output grid is t2r_lowall with a cell size of 75 meters. Smallest Z value was set to -50 in order to omit the -9999 values. Drainage enforcement was set to ENFORCE and the primary type of input data was set to spot.
    Date: 2008 (process 10 of 14)
    Using ArcMap 9.2 a filter was applied to the resulting grid. ArcToolbox - Spatial analyst tools - neighborhood - filter. The filter type was low pass, with the option to ignore NODATA in calculations. The output was lowall_filter. Because of extrapolation, there are a couple of places where the lowstand sticks above the ravinement (flooding) surface. To fix this use raster calculator: con([lowall_filter] <= [ravsurfall], [lowall_filter]). The effect of this calculation is to use the lowstand value where that value is less than or equal to the ravinement (flooding) surface. If the lowstand surface is greater than the ravinement (flooding) surface, set the value to the ravinement surface. Doing this maintains the proper surface relationships. The output is lowfilclip.
    Date: 29-Jun-2016 (process 11 of 14)
    Edits to the metadata were made to fix any errors that MP v 2.9.32 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). The source information was incomplete and had to be modified to meet the standard. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 20-Jul-2018 (process 12 of 14)
    USGS Thesaurus keywords added to the keyword section. 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: 18-Nov-2019 (process 13 of 14)
    Crossref DOI link was added as the first link in the metadata. 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: 08-Sep-2020 (process 14 of 14)
    Added keywords section with USGS persistent identifier as theme keyword. 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
  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, Reston, VA.

    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, Reston, VA.

    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?
    The R/V Rafael acquired data recording navigation using a Real Time Kinematic (RTK) GPS at a one second interval. The GPS antenna was mounted over the bathymetric sonar. The seismic pole mount system was on the starboard side and approximately 1.5 meters aft of the bathymetry system. No offset was added to the navigation for the seismic data. For seismic data collected with the IRIS system, an RTK GPS system was also used. The GPS antenna for IRIS was 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?
    For the Rafael seismic system, the transducers were located approximately 1 meter below the water surface. This offset was not adjusted for. For the IRIS system, the transducers are barely below the water surface, less than half a meter. This depth is not adjusted for. Although the seismic data were not tide corrected, the depth surfaces are related to a sea-floor surface based largely on swath bathymetry data that was tide corrected to mean lower low water.
  4. Where are the gaps in the data? What is missing?
    All useable seismic-reflection profiles collected in 2006 within Apalachicola Bay were used in the interpretation.
  5. How consistent are the relationships among the observations, including topology?
    Information unavailable from original metadata.

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 The public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the 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

    (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?
    These data are available as a 32-bit floating point raster in Environmental Systems Research Institute (ESRI) format. To utilize these data, the user must have software capable of viewing or importing an ESRI raster.

Who wrote the metadata?

Dates:
Last modified: 18-Mar-2024
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
Woods Hole Coastal and Marine Science Center
Woods Hole, MA

(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS. (updated on 20240318)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/open_file_report/ofr2012-1003/lowfilclipmeta.faq.html>
Generated by mp version 2.9.51 on Mon Mar 25 16:05:40 2024