ReadMe File - SEAX 96004 Sidescan-Sonar

README

Archive of Sidescan-Sonar Data
and DGPS Navigation Data
Collected During USGS Cruise SEAX 96004
New York Bight, 1 May - 9 June 1996

U.S. Geological Survey Open-File Report 01-95

by Jenna C. Hill, William C. Schwab and William W. Danforth

U.S. Geological Survey, Woods Hole Field Center, Woods Hole, MA 02543

INTRODUCTION

This DVD-ROM (Digital Versatile Disc-Read Only Memory) has been produced in accordance with the UDF (Universal Disc Format) DVD-ROM Standard and is therefore capable of being read on any computing platform that has appropriate DVD-ROM driver software installed.

Access to the data and information contained on this DVD-ROM was developed using the HyperText Markup Language (HTML) utilized by the World Wide Web (WWW). Development of the DVD-ROM documentation and user interface in HTML allows a user to access the information by using a variety of WWW information browsers (i.e. Microsoft Internet Explorer, Netscape) to facilitate browsing and locating information and data. To access the information contained on this disc with a WWW client browser, open the file 'index.htm' at the top level directory of this DVD-ROM with your selected browser. The HTML documentation is written utilizing some HTML 4.0 enhancements. The disc should be viewable by all WWW browsers but may not properly format on some older WWW browsers.

Also, some links to USGS collaborators and other agencies are available on this DVD-ROM. These links are only accessible if access to the Internet is available during browsing of the DVD-ROM.

The archived sidescan-sonar data may be downloaded and processed. Software is available on this DVD-ROM for viewing an individual swath using any computer running the UNIX operating system (Danforth, 1997). See the "readme" file in the BIN directory for details.

BACKGROUND

Beginning in 1995, the USGS, in cooperation with the U.S Army Corps of Engineers (USACE), New York District, began a program to generate reconnaissance maps of the sea-floor offshore of the New York-New Jersey metropolitan area, one of the most populated coastal regions of the United States. The goal of this mapping program is to provide a regional synthesis of the sea-floor environment, including a description of sedimentary environments, sediment texture, seafloor morphology, and geologic history to aid in understanding the impacts of anthropogenic activities, such as ocean dumping. This mapping effort differs from previous studies of this area by obtaining digital, sidescan sonar images that cover 100 percent of the sea floor.

This investigation was motivated by the need to develop an environmentally acceptable solution for the disposal of dredged material from the New York - New Jersey Port, by the need to identify potential sources of sand for renourishment of the southern shore of Long Island, and by the opportunity to develop a better understanding of the transport and long-term fate of contaminants by investigations of the present distribution of materials discharged into the New York Bight over the last 100+ years (Schwab and others, 1997). Data collected in 1996, USGS cruise SEAX 96004, augments data collected in 1995 with sidescan sonar and seismic reflection data collected within the New York Bight Apex region. This report is an archive of the sidescan-sonar data and DGPS navigation data collected in 1996.

CONTENTS

Directory DATA: The DATA Directory contains the raw sidescan-sonar data. These data were collected using a Datasonics100-kHz sidescan-sonar system and were logged on a Triton-Elics Internation, Inc., ISIS acquisition system. The sidescan-sonar data were collected at a range of 187.5 meters per side; 375 meter swath. The sidescan-sonar data are 16-bit binary; the format is summarized in a text file located in the DOC directory. The data description is also available in HTML format. The archived sidescan-sonar data are stored on 12 separate DVD-ROMs. The Field Data can be accessed from the main page.

Directory DOC: The DOC Directory contains ASCII documentation on the sidescan-sonar data file format collected using the ISIS system. This directory also contains ASCII copies of the cruise report and a description of the navigation data files contained in the NAV directory.

Directory NAV: The NAV Directory contains the navigation data that were collected during the sidescan-sonar component of the field program, using a USGS differential GPS system manufactured by Ashtech. Differential corrections were obtained from shore-based U.S. Coast Guard beacons.
WARNING: These data have not been checked for errors. Use with caution.

NAV sub-directory:

The files in this directory have been reformatted from the original raw navigation data file using the UNIX awk utility to allow for easier viewing. The awk file is located in the SCRIPTS sub-directory. The script, 'rformnav.awk', is an awk script written to reformat raw navigation data (from the "nav/rawnav directory) into six separate columns. The columns include: date/time, latitude, longitude, speed of vessel, heading, and depth (meters). The "awk" or "nawk" (new awk) command is available on any system employing the UNIX operating system.

Every navigation fix from the original raw data has been preserved. The navigation is stored in ASCII files with six fields separated by tabs. Each file represents a separate cruise day (i.e. jd124web.txt represents Julian Day 124). Navigation fixes are at ~10 second intervals.

Field 1: Date and Time (julian day:hour (UTC):minute:second)

Field 2: Latitude (ie. 32d59375 )

Field 3: Longitude (ie. -79d968975)

Field 4: Speed (computed from the navigation)

Field 5: Heading (computed from the navigation)

Field 6: Water Depth (derived from an Odem 3.5 kHz sub-bottom profiler).
Depths are in meters, but have not been corrected for the depth of the transducer, which was about 2 m below the sea surface, nor for the tide (for tidal information, see http://www.nos.noaa.gov).

RAWNAV sub-directory:

The raw USGS differential GPS data is located in this directory. These files (i.e. jd128) represent the data as originally recorded on floppy disk aboard ship. The data are in NEMA format and contain the $GPGGA string.

SCRIPTS sub-directory: The SCRIPTS sub-directory contains the awk script file used to reformat the raw navigation into a format more suitable for on-screen viewing and printing. See the readme.txt file in this sub-directory for details.

Directory HTMLDOCS: The HTMLDOCS Directory contains the necessary HTML files to allow the user access to the DVD-ROM via any World Wide Web (WWW) browser.

Directory PLOTS:

PDF sub-directory:

The PDF sub-directory contains the Adobe Portable Document Format (PDF) navigation plots. These files require Adobe Acrobat Reader for viewing (available free from www.adobe.com).

JPG sub-directory:

The JPG sub-directory contains the navigation plots in JPEG format.

Directory BIN: The BIN Directory contains the ShowImage program to view the raw data files on screen (Danforth, 1997). The program only runs on systems using the UNIX operating system. Included are three separate sub-directories containing the executable for the appropriate operating system: sgi, digunix, linux. See the readme.txt or readme.htm files in the BIN directory for details.

Directory IMAGES: The IMAGES Directory contains GIF and JPEG images that are used by HTML hyperlinks.

REFERENCES

Danforth, W.W., 1997, Xsonar/ShowImage: A Complete System for Rapid Sidescan-Sonar Processing and Display, U.S. Geological Survey Open-File Report 97-686, pp 1 - 79.

Schwab, W.C., Thieler, E.R., Denny, J.F., Danforth, W.W. 2000. Seafloor Sediment Distribution Off Southern Long Island, New York: U.S. Geological Survey Open-File Report 00-243, 3 Sheets.

DISCLAIMER

This Digital Versatile Disc-Read Only Memory (DVD-ROM) publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Although all data published on this DVD-ROM have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data, software, or related materials.

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