ASV_LINES_CALIBRATED.SHP: Polyline-M Shapefile of Navigation Tracklines for Autonomous Surface Vessel IRIS Chirp Seismic Data in Apalachicola Bay collected on U.S. Geological Survey Cruise 06001 (Geographic, WGS84)

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Frequently-anticipated questions:

What does this data set describe?

ASV_LINES_CALIBRATED.SHP: Polyline-M Shapefile of Navigation Tracklines for Autonomous Surface Vessel IRIS Chirp Seismic Data in Apalachicola Bay collected on U.S. Geological Survey Cruise 06001 (Geographic, WGS84)
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 <> and <>.
This shapefile contains the IRIS chirp seismic tracklines as polyline-m files with the measurement value of shots. These tracklines act as a data archive, as well as aiding the spatial relation of the seismic-reflection profiles with other GIS data available in the same area.
  1. How should this data set be cited?

    Cross, VeeAnn A. , and Foster, David S. , 2012, ASV_LINES_CALIBRATED.SHP: Polyline-M Shapefile of Navigation Tracklines for Autonomous Surface Vessel IRIS Chirp Seismic Data in Apalachicola Bay collected on U.S. Geological Survey Cruise 06001 (Geographic, 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, 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?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

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

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • String (211)

    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 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees.

      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.

  7. How does the data set describe geographic features?

    ESRI polyline shapefile (Source: ESRI)

    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    An abbreviated text field which provides a unique line name associated with each point of data collection. The shorter name is easier to work with in the seismic interpretation software. (Source: Data processor.)

    Character set.

    Calendar year the data were collected. (Source: Data processor.)

    2006Year in which the data were collected.

    This number represents the Julian day of data collection based on UTC time. Julian day is the integer number representing the interval of time in days since January 1 of the year. (Source: Data processor.)

    Range of values

    Text field indicating of the recoding software of the seismic line was the Discover software. (Source: Data processor.)

    noThe Discover software was not used to record the data
    yesThe Discover software was used to record the data.

    The divisor needed to convert the navigation recorded in the SEG-Y headers to decimal degrees. The first number represents the divisor of the longitude, while the second number indicates the divisor needed for the latitude. (Source: Data processor.)

    Character set.

    The prefix of the original seismic filename used to extract the navigation and generate the JPEG images. (Source: Data processor.)

    Character set.

    The platform used to collect the original seismic data was the Woods Hole Coastal and Marine Science Center's Autonomous Surface Vessel (ASV) IRIS (Independently (or) Remotely Influenced Surveyor). Details of the platform can be found on the following web page: <>. IRIS is configured with an EdgeTech FFSB 424 chirp sub-bottom profiler that operates within a 4-24 kHz frequency range. The vehicle is navigated using Real-Time Kinematic (RTK) GPS. The antenna is mounted directly on the platform to minimize navigational error.

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
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2266 (voice)
    (508) 457-2310 (FAX)

Why was the data set created?

This shapefile provides the ASV IRIS seismic tracklines as a calibrated, linear-referenced shapefile. The calibration is based on shot point navigation. Not only do these lines provide the location of the IRIS tracklines, they can also be used to correlate other GIS data with the actual seismic-reflection profiles based on shot point number.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    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 17)
    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 Coastal and Marine Science Center, U.S. Geological Survey.

    Person who carried out this activity:

    Tom O'Brien
    U.S. Geological Survey
    Marine Geophysical Systems Expert
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2246 (voice)
    5084572310 (FAX)

    Date: 2006 (process 2 of 17)
    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
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2271 (voice)
    (508) 457-2310 (FAX)

    Date: 2006 (process 3 of 17)
    A csh script utilized Seismic Unix (v. 4.0) to extract all of the unique navigation points from the SEG-Y header within the seismic data. These values were written to a comma-delimited text file. In addition to extracting the navigation, the csh script was used to generate JPEG images of each seismic profile. 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. The divisors necessary for proper navigation extraction are contained in the attribute field "divisors" and are in the format "longitude divisor/ latitude divisor". This process step and all subsequent process steps were performed by the same person - VeeAnn A. Cross.

    Person who carried out this activity:

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)

    Date: 2006 (process 4 of 17)
    The individual comma-delimited text files were then concatenated to generate a single navigation text file. This file was edited to remove invalid positions (usually latitude and longitude values of 0). In addition, calendar year and Julian day values were edited as necessary in order to reflect appropriate values. Finally, a header was added to the navigation text file in order to describe each column of data.

    Date: 2006 (process 5 of 17)
    The navigation text file was added to ArcMap 9.1 as an XY point event layer and converted to a point shapefile.

    Date: 2007 (process 6 of 17)
    The attribute "lmarkname" was added to the shapefile. This attribute will be used as the unique line name when loading the data into Landmark SeisWorks software. Seismic lines containing circles or turns were broken into multiple segments and assigned a unique line name by appending an "a" or "b" etc. to the line name. Landmark can load a portion of a SEGY file by loading the line segment that corresponds to the shot point navigation. (i.e. Splitting a SEGY file into segments is unnecessary, only the navigation needs to be split). During the initial days of surveying, the seismic acquisition system simultaneously recorded multiple files per survey line, creating some data redundancies. These overlapping portions of the survey line do not have a value entered in the "lmarkname" attribute

    Date: 2007 (process 7 of 17)
    All records that do not have a blank in the "lmarkname" attribute are selected and saved to a new point shapefile that will be used to load SEG-Y data into Landmark software.

    Data sources used in this process:

    • allasvpntnav_mod.shp

    Data sources produced in this process:

    • allasv4landmark.shp

    Date: 2007 (process 8 of 17)
    This point layer was then converted to a polyline shapefile using the Points to Lines v2 script in VAC Extras v. 1.98 (a collection of tools used in the USGS Woods Hole Coastal and Marine Science Center). The lines are based on a unique identifier in the point attribute table (lmarkname). The first occurrence of the following attributes is carried over: filename, shot, year, jday, seistime.

    Data sources used in this process:

    • allasv4landmark.shp

    Data sources produced in this process:

    • allasv4landmark_lns.shp

    Date: 2007 (process 9 of 17)
    The attributes "discover" and "divisors" were added to the attribute table. These attributes help to discern how the data was handled immediately after acquisition. In particular, the "divisors" attribute will be beneficial to anyone working with the SEG-Y data and will be needed to extract the navigation from the headers.

    Data sources used in this process:

    • allasv4landmark_lns.shp

    Data sources produced in this process:

    • allasv4landmark_lns.shp

    Date: 2007 (process 10 of 17)
    The polyline shapefile was converted to a route using ArcMap 9.2 - ArcToolbox - Linear referencing - Create Routes. Input: allasv4landmark_lns; route identifier: lmarkname; output: asvlmark_route.shp; rest of the parameters at the defaults ( measure source - length; coordinate priority - upper_left; measure factor - 1; measure offset - 0; ignore spatial gaps - checked; build index - checked).

    Date: 2008 (process 11 of 17)
    The original point navigation will be used to calibrate the polylines based on shot number. However, before this can be done, any points with duplicate location need to be removed. Within ArcMap 9.2, using XTools Pro v. 5.2 - Table operations - Find Duplicates set the output to allasv_nodupes.shp. Other parameters: add feature to current map, create spatial index, compare by shape - check box to remove duplicates; index field name - index. Deselect the option to add ID field of the source feature. After this was done, a comparison showed the original shapefile had 123157 points and the new one had 122950 points.

    Date: 2008 (process 12 of 17)
    Sort the new shapefile using VACExtras v 2.0, VAC Extras - Feat Conv - Table Sort. Primary sort is lmarkname in ascending order, secondary sort is shot in ascending order. Output: all asv_nodupes_sort.shp.

    Date: 2008 (process 13 of 17)
    Now I need to look for loop back sections in the seismic tracklines. The easiest way to do this was to find problems with a calibrated route, so within ArcMap 9.2 calibrate the route using ArcToolbox - Linear Referencing - Calibrate Routes. Input: asvlmark_route; route identifier: lmarkname; input points: allasv_nodupes; point identifier: lmarkname; measure field: shot; output route feature class:asvlmark_route_Calibratedtmp.shp. Rest of the fields were left at their default values. Once the route was calibrated, create the end hatches for the routes using the shapefile Properties - Hatches - Add Hatch Definition. Add end hatch definition set the hatch to a marker, tolerance 0 and lateral offset 0. With the hatches displayed, the point shapefile can be edited to sort out the bad portions.

    Date: 2008 (process 14 of 17)
    Taking the cleaned point shapefile, generate a new polyline from these points. Using VACExtras 2.0 - VAC Extras - Feat Conv - Points to Line v2. The unique line identifier: lmarkname. Fields to transfer first occurrence: filename, shot, year, jday, seistime, discover, divisors. Output to asv_lines.shp.

    Date: 2008 (process 15 of 17)
    Convert the line to a route using ArcMap 9.2 - ArcToolbox - Linear referencing - Create Routes. Input: asv_lines; route identifier: lmarkname; output: asv_lines_Routes.shp. Rest of the parameters left to default.

    Date: 2008 (process 16 of 17)
    Calibrate the route using ArcMap 9.2 - Linear Referencing - Calibrate Routes. Input: asv_lines_Routes; route identifier: lmarkname; input points: allasv_nodupes_sort; point identifier: lmarkname; measure field: shot; output route feature class: asv_lines_Calibrated.shp. Rest of the parameters left at the defaults.

    Date: 2008 (process 17 of 17)
    Add the following attributes to the calibrated shapefile: year, jday, discover, divisors, orig_fname. In order to populate these fields, join asv_lines_Calibrated to asv_lines with the join field set to lmarkname in both shapefiles. Once the files are joined, field calculator is used to copy the attribute values form the asv_lines attributes to the asv_lines_Calibrated attributes.

  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?

  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, or extremely short lines, were deleted. Some lines acquired seismic data, but little or no navigation. These lines are also excluded. One line was re-run, so the original problematic line was excluded. The list of collected seismic lines excluded from this and subsequent datasets is as follows: Julian day 155 - apalachicola000 (rerun), apalachicola020 (too short), apalachicola027 (insufficient navigation). Julian day 160 - day160001 (insufficient navigation). Julian day 165 - day165001 (too short). Julian day 172 - JD172010 (too short), JD172014 (too short), JD172025 (too short). Julian day 173 - JD173009 (too short). Julian day 174 - JD174010 (too short).

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

    All the data were handled in the same manner. 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.
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)

  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 data available in ESRI polyline-m shapefile format. The user must have software capable of uncompressing the WinZip file and reading/displaying the shapefile.

Who wrote the metadata?

Last modified: 12-Apr-2012
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
384 Woods Hole Rd.
Woods Hole, MA 02543-1598

(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)

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 17:10:42 2012