GIS of Selected Geophysical and Core Data in the Northern Gulf of Mexico Continental Slope Collected by the U.S. Geological Survey

OF 2005-1071 Home

Overview

Geologic Findings

GIS Data Catalog

References Cited

Acknowledgements

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GIS Data Catalog

The GIS data assembled in this report are organized into five categories, and the contents of each are described in greater detail in the subsections that follow. These categories, in alphabetical order, include (1) Assessment, (2) Background, (3) Cores, (4) Seismic, and (5) Sidescan. The assessment category includes previously published shapefiles (Charpentier and others, 1996) that were used in an assessment of gas hydrates in the Gulf of Mexico (Collett, 1995). Source information is provided in the metadata that accompanies each shapefile. The background category includes shapefiles and imagery depicting coastline, bathymetry, lease information, platform locations, the Exclusive Economic Zone (EEZ) boundary, and sea floor names. Source information is provided in the metadata for each of these public datasets. The coring category includes the locations of cores collected by the USGS and descriptions and analyses of the cores. The visual descriptions are consistent within each of the coring programs, but differ between programs because of different project goals. The seismic category includes trackline navigation, shot point or time annotations, and, for the digitally acquired seismic data, images of each of the profiles. The regional set of seismic profiles collected during the GLORIA sidescan sonar survey is only in analog form (EEZ-SCAN85 Scientific Staff, 1987). The sidescan-sonar category includes imagery and interpretive shapefiles for each of three surveys conducted by the USGS in the deep-water part of the Gulf of Mexico. Some of the interpretations have been published previously in digital form, others are digitized from paper publications, and others are new interpretations.

The data layers provided below are compatible for use in Environmental Systems Research Institute's (ESRI) software - either ArcView 3.3 or ArcGIS. This DVD contains an ESRI ArcView 3.3 Geographic Information System (GIS) project file: gomgis.apr, which is stored at the top level directory of this publication. The project file contains a startup script which will prompt the user for the directory path of the project file. This information is needed in order to establish 'hotlinks' found within the project file. The project file contains five views with each view representing one of the five data categories. The data layers presented in these views are in the geographic coordinate system. In each view only some of the interpretive shapefiles are loaded for clarity, and the others can be loaded as desired. For consistency, all data presented in this publication is referenced to the NAD83 or WGS84 datum. Many of the original datasets were referenced to the NAD27 datum.

For those users who do not have ArcView 3.2 or later necessary to open the gomgis.apr file, the individual GIS data layers can be viewed with a compatible GIS viewer, or a free GIS viewer such as ArcExplorer. This GIS data viewer is available from ESRI (www.esri.com). Please note that the ArcExplorer software is limited to the Microsoft Windows operating systems and some UNIX operating systems.

Federal Geographic Data Committee (FGDC) metadata is provided for each of the individual data layers. This metadata, along with the individual GIS data layer, is compressed into a downloadable archive file in WinZip format. Users who do not have software capable of uncompressing the archived zip files can obtain free versions of compatible software from Winzip Computing, Inc. (www.winzip.com) or Pkware, Inc (www.pkzip.com).

 

(1) ASSESSMENT

A thumbnail of figure 5 showing estimated hydrate thickenss.

Information used in a 1995 assessment of gas hydrates in the Gulf of Mexico is included in this GIS (Fig. 5). The data are described in detail by Charpentier and others (1996), and the assessment has been summarized by Collett (1995). The shapefiles from this assessment that are included are listed below and available from subfolders within the data/assessments folder. For completeness, all the shapefiles used for the assessment of gas hydrates are presented including the EEZ boundary even though a second EEZ boundary shapefile provided by the National Oceanic and Atmospheric Administration (NOAA) is available in the data/background folder. These two shapefiles differ in that the assessments shapefile outlines the federal waters (3 nautical miles from the coast to the international boundary) while the EEZ boundary presented in the background section was compiled by NOAA and just shows the international boundary. The location of the international boundary in the two shapefiles varies slightly, but the EEZ boundary from the assessments category is necessary for consistency with the other assessment data presented here.

Data Layer Name and Description
Files
atmx_bat.shp: Bathymetry presented as 200, 500, 1000, 2000, 3000, 4000 and 5000 m contour polylines of the Gulf of Mexico and US Atlantic.
atmx_eez.shp: United States Exclusive Economic Zone (EEZ) polyline of the Gulf of Mexico and the US Atlantic.
atmx_gtg.shp: Contour polylines showing the geothermal gradient (degrees C/100 m) of the Gulf of Mexico and US Atlantic.
atmx_hys.shp: Contour lines showing the calculated thickness of the hydrate stability zone (meters) of the Gulf of Mexico and the US Atlantic.
atmx_sbt.shp: Contour lines of seabed temperature (degrees C) of the Gulf of Mexico and the US Atlantic.
atmx_sed.shp: Contour lines of sediment thickness (meters) of the Gulf of Mexico and the US Atlantic.
atmx_toc.shp: Contour lines of the total organic carbon in sediment (percent) of the Gulf of Mexico and the US Atlantic.
atmx_tocpoly.shp: Polygon showing areas where total organic carbon exceed 0.5% of the Gulf of Mexico and the US Atlantic.

 

(2) BACKGROUND

A thumbnail of figure 6 showing background data.

Useful reference information on the Gulf of Mexico that has already been published either by the USGS or other government agencies is included here as background data (Fig. 6). These data are available from subfolders of the data/background folder. In addition, these data and their online sources are listed below. Of note: the data contained in this publication that originated from the Minerals Management Service has been reprojected from the original NAD27 datum to the NAD83 datum. Many of the files available from other online resources are still referenced to the NAD27 datum. The EEZ boundary presented in this section (useez.shp) was compiled by NOAA using source information taken from the 1995 Federal Register titled "Exclusive Economic Zone and Maritime Boundaries: Notice of Limits" (nauticalcharts.noaa.gov/csdl/EEZ.HTM)

Data Layer Name and Description
Files
bathyc.shp: Bathymetric contours for the Gulf of Mexico. These generalized contours and the metadata can also be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/centgulf/lcs/data.html
carib_wvs_geo_wgs84.shp: Outline of islands in the Caribbean Sea. The data and metadata can be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/gloria/data.html
mexico-cam_wvs_geo_wgs84.shp: Outline of Mexico and Central America. The data and metadata can also be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/gloria/data.html
leaseblk_nad83.shp — Lease block locations and names for the Gulf of Mexico. This shapefile originated from the Minerals Management service and can be downloaded from their Web site:
http://www.gomr.mms.gov/homepg/
pubinfo/repcat/arcinfo/index.html

The data and metadata can also be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/centgulf/lcs/data.html
platform_nad83.shp — Locations of offshore oil and gas platforms in the Gulf of Mexico. This shapefile originated from the Minerals Management service and can be downloaded from their Web site:
http://www.gomr.mms.gov/homepg/
pubinfo/repcat/arcinfo/index.html
protrac_nad83.shp — Protraction diagram for the Gulf of Mexico. This shapefile originated from the Minerals Management service and can be downloaded from their Web site:
http://www.gomr.mms.gov/homepg/
pubinfo/repcat/arcinfo/index.html

The data and metadata can also be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/centgulf/lcs/data.html
crm_hillshade.tif — Shaded-relief image derived from the NOS Coastal Relief Model dataset available from their Web site:
http://www.ngdc.noaa.gov/mgg/coastal/
coastal.html
gomnames.shp — Names of physiographic features in the Gulf of Mexico, which have been compiled by the National Geophysical Data Center, and are available at the following Web site:
http://www.ngdc.noaa.gov/mgg/ibcca/
allus80k.shp — Outline of the coterminous United States. The data and metadata can be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/centgulf/lcs/data.html
state_bounds.shp — State boundaries for the coterminous United States. The data and metadata can be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/centgulf/lcs/data.html
us_eez.shp — Line that demarks the seaward limit of the Exclusive Economic Zone of the US. The data and metadata can be downloaded from the following USGS Web site:
http://coastalmap.marine.usgs.gov/regional/
contusa/gomex/centgulf/lcs/data.html

 

(3) CORING

A thumbnail of figure 7 showing core locations.

Results from three coring programs that have been completed by the USGS in the deep Gulf of Mexico are presented in this GIS as well. These coring programs include one completed on the Mississippi Fan and along the base of the Florida Escarpment in 1990 aboard the R/V FARNELLA, a second completed in 1997 on the Louisiana continental slope aboard the R/V GYRE, and a third one completed in 2002 on the Texas and Louisiana slope aboard the R/V MARION DUFRESNE using a giant piston corer, a 9 m-long box corer, and a gravity corer. Core locations are shown in Figure 7. Scanned field descriptions of the cores and drafted visual summaries of most of the cores are included on the DVD-ROM in subfolders of the data/cores folder. A summary of each coring program is given below. The Information Archives of the USGS Woods Hole Science Center (http://woodshole.er.usgs.gov/operations/ia/index.html) also contains information on these cores.

FARNELLA — Sixty-seven piston and gravity cores were collected during April, 1990 on the Mississippi Fan and along the base of the Florida Escarpment in the eastern Gulf of Mexico. Visual descriptions of the cores were completed in the field, and subsequently visual core logs were compiled and X-rays were taken of parts of several cores. These results were compiled and published by Paskevich and others (2000), and have been integrated into this GIS. These data are available from the data/cores/farnella folder and subfolders.

Data Layer Name and Description
Files
farn_cores_nad83.shp — locations of cores collected during this cruise. The JPEG versions of the visual summaries that were compiled for the cores on the Mississippi Fan have been hotlinked to the core locations. Additional information including field descriptions and core x-rays are available from subfolders (data/cores/farnella/fdesc and data/cores/farnella/xrays)

 

GYRE-97006 — Thirty-four piston and gravity cores were collected from the western Louisiana continental slope during April 1997. Core logs, visual descriptions of the cores, and physical properties measurements that were completed in the field are included on this DVD-ROM. The field descriptions were scanned and are included as PDF files. The physical properties measurements include sonic velocity and density measurements that were measured at 2 cm intervals and are included as Microsoft Excel spreadsheets. These data are available from the data/cores/gyre97 folder and subfolders.

Data Layer Name and Description
Files
gyre_cores.shp — locations of cores collected during the GYRE 97006 cruise on the Louisiana continental slope. The JPEG versions of the visual summaries that were compiled for the cores have been hotlinked to the core locations. Additional information including fields descriptions and physical properties are available from subfolders (data/cores/gyre97/fdesc and data/cores/gyre97/phys_prop)

 

MARION DUFRESNE — Thirty-two of the cores collected during this cruise are included in this GIS. Of the thirty-two cores, 17 were collected with a piston corer, 8 with a gravity/flux (heat flow) corer, 4 with a gravity corer, and 3 with a giant box corer. Twenty-three of these cores were described on board the ship, and the descriptions are included in this GIS. The remaining 9 cores have not yet been described. These data are available from the data/cores/md folder and subfolders. These visual summaries of these cores are in PDF format rather than JPEG format. In order to ensure that the hotlink to these summaries works, the user should have a copy of Adobe Acrobat Reader on their computer. A free copy of the software is available from Adobe (http://www.adobe.com/products/acrobat/alternate.html)

Data Layer Name and Description
Files
md_cores_wdesc.shp — locations of cores collected during a cruise aboard the MARION DUFRESNE from the northern Gulf of Mexico continental slope for which core descriptions are available. The PDF versions of the visual summaries compiled for the cores have been hotlinked to the core locations. Additional information regarding the physical properties of the cores is available from the phys_prop subfolder (data/cores/md/phys_prop)

 

(4) SEISMIC

A thumbnail of figure 8 showing seismic tracklines.

Six different seismic-reflection surveys have been conducted in the deep-water part of the Gulf of Mexico by the USGS since 1982. The earliest of these datasets was collected during the GLORIA surveys in 1982 and 1985. While these data provide comprehensive coverage of the entire deep Gulf of Mexico EEZ, they are only available in analog form (EEZ Scan 85 Scientific Staff, 1987). The remaining five seismic datasets were all logged digitally, and have been archived in SEG-Y format (Nealon and others, 1999; Foster and others, 2000; Hart and others, 2002; Hart and others, 2005). Tracklines for these five surveys are includes in this GIS (Fig. 8), and JPEG or TIFF images of the seismic profiles are hotlinked to the tracklines.

1982-1985 These data are available from the data/seismic/1982_1985/nav subfolders.

Data Layer Name and Description
Files
gloriatracks.shp — Tracklines along which single-channel seismic profiles were collected during the GLORIA program. Details about the airgun and hydrophone and paper copies of the profiles can be found in EEZ-Scan 1985 Scientific Staff (1987).
farn82_7pnts.shp — Points at an hourly interval along the survey tracks for one of the four cruises completed for the GLORIA program aboard the R/V FARNELLA.
farn85_1pnts.shp - Points at an hourly interval along the survey tracks for one of the four cruises completed for the GLORIA program aboard the R/V FARNELLA.
farn85-2pnts.shp - Points at an hourly interval along the survey tracks for one of the four cruises completed for the GLORIA program aboard the R/V FARNELLA.
farn85_3pnts.shp - Points at an hourly interval along the survey tracks for one of the four cruises completed for the GLORIA program aboard the R/V FARNELLA.

 

1997 The GIS data are available from the data/seismic/1997/nav folder with the accompanying TIFF profiles available from the data/seismic/1997/profiles folder.

Data Layer Name and Description
Files
g97_1mnline.shp — Tracklines along which single-channel seismic profiles were collected aboard the R/V GYRE in 1997 on the continental slope offshore of the western part of Louisiana. Each profile was saved as a TIFF image and is hotlinked to the correct trackline in the GIS
g97_1mnpnts - Points every 1 minute along the tracklines where seismic data were collected.
g97_15mnpnt.shp — Points every 15 minutes along the tracklines where seismic data were collected.

 

1998 The GIS data are available from the data/seismic/1998/nav folder with the accompanying JPEG profiles available from the data/seismic/1998/profiles folder.

Data Layer Name and Description
Files
gom98line.shp — Tracklines along which high-resolution seismic reflection data were collected in the Mississippi Canyon area aboard the R/V TOMMY MONROE. Each profile was saved as a JPEG image and is hotlinked to the correct trackline in the GIS.
gom98shtallg.shp — Common depth points at 20 to 65 shot intervals.

 

1999 The GIS data for the multichannel seismics are available from the data/seismic/1999/mcs/nav folder with the accompanying JPEG profiles available from the data/seismic/1999/mcs/profiles folder. The GIS data for the chirp seismics are available from the data/seismic/1999/chirp/nav folder with the accompanying JPEG profiles available form the data/seismic/1999/chirp/profiles folder.

Data Layer Name and Description
Files
gom99lmcs.shp — Tracklines along which high-resolution multichannel seismic-reflection data were collected on the upper continental slope of the Garden Banks and Green Canyon regions of the northern Gulf of Mexico. Each profile was saved as a JPEG image and is hotlinked to the correct trackline in the GIS.
gom99shtallg.shp — Shot points at approximately a 40-shot interval for the multichannel seismic data.
l1_5ln.shp — Tracks of lines 1-5 of R/V GYRE cruise 99002 along which chirp subbottom profiles were collected using the Benthos SIS-1000 sidescan sonar and subbottom profiling system. Each profile was saved as a JPEG image and is hotlinked to the correct trackline in the GIS.
l15_27ln.shp - Tracks of lines 15-27 of R/V GYRE cruise 99002 along which chirp subbottom profiles were collected using the Benthos SIS-1000 sidescan sonar and subbottom profiling system. These data fall within the area of the SIS-1000 sidescan sonar survey on the upper slope offshore of Louisiana. Each profile was saved as a JPEG image and is hotlinked to the correct trackline in the GIS.
l1_5sp.shp — Shot points for the chirp data collected along lines 1-5. The points are spaced mostly at a 60 shot interval.
l1_5sp100g.shp — Shot points for the chirp data collected along lines 1-5. The points are spaced at a 100 shot interval.
l15_27sp.shp — Shot points for the chirp data collected along lines 15-27. The points are spaced mostly at a 60 shot interval.
l15_27sp100g.shp — Shot points for the chirp data collected along lines 15-27. The points are spaced at a 100 shot interval.

 

2002 The GIS data are available from the data/seismic/2002/nav folder with the accompanying JPEG profiles available from the data/seismic/2002/profiles folder.

Data Layer Name and Description
Files
md02chirpln.shp — Tracklines along which chirp subbottom profiles were collected to select giant piston core sites during a cruise aboard the R/V MARION DUFRESNE. Each profile was saved as a JPEG image and is hotlinked to the correct trackline in the GIS.
md02chirppnt.shp — Points at approximately a 7-second interval along the R/V MARION DUFRESNE tracklines.

 

2003 The Atwater Valley GIS data are available from the data/seismic/2003/atwater/nav folder with the accompanying JPEG profiles available from the data/seismic/2003/atwater/profiles folder. The Keathley Canyon GIS data are available from the data/seismic/2003/keathley/nav folder with the accompanying JPEG profiles available from the data/seismic/2003/keathley/profiles folder.

Data Layer Name and Description
Files
av_g103gm_lines.shp — Tracklines along which high-resolution 24-channel seismic-reflection profiles were collected using a 13 in3 GI gun sound source in the Atwater Valley area in the central Gulf of Mexico. Each profile was saved as a JPEG image and is hotlinked to the correct trackline in the GIS.
g1cdp_nav_av_geo.shp — Common Depth Points for the seismic data collected during the Atwater Valley survey. Every CDP is shown.
kc_g103gm_lines.shp — Tracklines along which high-resolution 24-channel seismic-reflection profiles were collected using a 13 in3 GI gun sound source in the Keathley Canyon area in the western Gulf of Mexico. Each profile was saved as a JPEG image and is hotlinked to the correct trackline in the GIS.
g1cdp_nav_kc_geo.shp - Common Depth Points for the seismic data collected during the Keathley Canyon survey. Every CDP is shown.

 

(5) SIDESCAN

GLORIA

A thumbnail of figure 9 showing sidescan-sonar imagery locations.

The first of the sidescan datasets is the regional GLORIA sidescan sonar survey of the entire deep-water part of the US EEZ in the Gulf of Mexico (Fig. 9). GLORIA (Geologic LOng-Range Inclined Asdic) is a low frequency sidescan sonar system which operates at 6.5-6.8 kHz, and for most of this survey was set to scan 22.5 km to each side of the tow vehicle (EEZ-Scan85 Scientific Staff, 1987). The GLORIA imagery was acquired in 1982 and 1985 and the imagery presented here is drawn from the report by Paskevich (2000). For this report the imagery has been reprojected to a Geographic coordinate system with central latitude of 26d 15’N based on the WGS 84 datum. The georeferenced imagery has a pixel size of 250 m and is available from the data/sidescan/imagery/gloria/geog folder.

 

Data Layer Name and Description
Files
gloria_geog.tif — TIFF image (and accompanying TIFF world file) of the GLORIA mosaic of the Gulf of Mexico.

 

Seven interpretive GIS overlays are included in the data/sidescan/interpretation/gloria/ folder. Only some of these shapefiles are loaded into the 'Sidescan' view available in the gomgis.apr project file.

Data Layer Name and Description
Files
gloria_coverage_nad83.shp — Outline of the extent of the GLORIA survey (Paskevich, 2000) and subsequently reprojected to the NAD83 datum, geographic coordinate system.
gloria_geology_nad83.shp - The original geologic interpretation of the GLORIA imagery (EEZ-SCAN Scientific Staff, 1987) that was converted to ArcView format by Paskevich (2000) and subsequently reprojected to the NAD83 datum, geographic coordinate system.
morphology.shp — A modification of the original geologic interpretation published by Paskevich (2000), which highlights the different geomorphic provinces of the region along with modifications from a subsequent publication by Twichell and others (2000), which maps the extent of the Bryant Canyon and Fan system.
masswasting.shp — Interpretation of the locations of mass-wasting deposits based on the GLORIA imagery and high-resolution seismic reflection profiles. The interpretation integrates results from the following reports; EEZ-SCAN Scientific Staff (1987), Twichell and others (1990), Twichell and others (1991a, b), Twichell and Delorey (1996), Twichell and others (2000), and Twichell and Cooper, 2000).
gloria_bright_nad83.shp — Interpretation of location of high backscatter on the GLORIA sidescan sonar imagery that, where ground-truth information is available, coincides with large seep, hardground, and/or hydrate sites. This interpretation was completed by the senior author based on integrating the GLORIA backscatter information with multibeam bathymetric data and published locations of seeps and hydrates (Booth and others, 1996; Kennicutt and others, 1988).
seeps.shp — Locations of known sites of hydrocarbon seeps on the sea floor derived from the published literature as of 1996 (Booth and others, 1996).
hydrates.shp — Published locations of sites where gas hydrate is exposed on the sea floor as of 1996 (Booth and others, 1996).

 

SeaMARC

 
A thumbnail of figure 9 showing sidescan-sonar imagery locations.

The second of the sidescan datasets is a mid-range sidescan sonar survey of a portion of the Mississippi Fan (Fig. 9). The SeaMARC 1A system is a deep-towed sidescan-sonar system that operates at 30-kHz (Kosalos and Chayes, 1983), and provides imagery from a 5-km wide swath at a pixel resolution of 25 m. The SeaMARC 1A imagery was first published in digital form by Paskevich and others (2001), and a more detailed discussion of the data and scientific results are included in that report. Both enhanced and unenhanced imagery projected to UTM (Zone 15) as well as a geographic coordinate system are included on this DVD-ROM. in subfolders of the data/sidescan/imagery/seamarc/ folder. All georeferencing information is based on the WGS84 datum.

 

Data Layer Name and Description
Files
seamarc_engeog.tif — Enhanced SeaMarc IA TIFF mosaic, geographic coordinate system, WGS84 datum. Available in the data/sidescan/imagery/seamarc/enhanced/geog folder.
seamarc_enutm.tif — Enhanced SeaMarc IA TIFF mosaic, UTM projection (Zone 15, WGS84 datum). Available in the data/sidescan/imagery/seamarc/enhanced/utm folder.
seamarc_ungeog.tif — Unenhanced SeaMarc IA TIFF mosaic, geographic coordinate system, WGS84 datum. Available in the data/sidescan/imagery/seamarc/raw/geog folder.
seamarc_unutm.tif — Unenhanced SeaMarc IA TIFF mosaic, UTM projection (Zone 15, WGS84 datum). Available in the data/sidescan/imagery/seamarc/raw/utm folder.

 

In addition to the imagery, four interpretive GIS overlays are included in the data/sidescan/interpretation/seamarc folder.

Data Layer Name and Description
Files
interp.shp — Interpretation of depositional features on the SeaMARC 1A imagery (Paskevich and others, 2001).
channel.shp — Interpretation showing location of small channels identified on the SeaMARC 1A imagery (Paskevich and others, 2001).
lobe.shp — Interpretation showing the extent of the depositional lobe that was identified in the GLORIA imagery and partially surveyed by SeaMARC 1A (Paskevich and others, 2001).
seamarc_coverage.shp — Extent of the SeaMARC 1A sidescan survey (Paskevich and others, 2001).

 

SIS-1000

A thumbnail of figure 9 showing sidescan-sonar imagery locations.

The third sidescan dataset is a high-resolution survey of a small portion of the upper Louisiana Continental Slope (Fig. 9). These data were collected in 1999 with a Benthos SIS-1000 system, which was set to image 750 m to each side of the tow vehicle. The sidescan imagery was collected in concert with seismic-reflection data that are summarized in reports by Foster and others (2000) and Cooper and others (1999). Versions of the georeferenced sidescan TIFF mosaic can be found in subfolders of the data/sidescan/imagery/sis1000 folder. The enhanced geographic image is included in the 'Sidescan' view in the gomgis.apr project file.

 

Data Layer Name and Description
Files
sis_engeog.tif — Enhanced SIS-1000 sidescan TIFF mosaic, geographic coordinate system, WGS84 datum. Available in the data/sidescan/imagery/sis1000/enhanced/geog folder.
sis_enutm.tif — Enhanced SIS-1000 sidescan TIFF mosaic, UTM projection (Zone 15, WGS84 datum). Available in the data/sidescan/imagery/sis1000/enhanced/utm folder.
sis1000un_geog.tif — Unenhanced SIS-1000 sidescan mosaic, geographic coordinate system, WGS84 datum. Available in the data/sidescan/imagery/sis1000/raw/geog folder.
sis1000_unutm.tif — Unenhanced SIS-1000 sidescan mosaic, UTM projection (Zone 15, WGS84 datum). Available in the data/sidescan/imagery/sis1000/raw/utm folder.

 

In addition to the imagery, three GIS interpretive overlays are included in the data/sidescan/interpretation/sis1000 folder.

Data Layer Name and Description
Files
sis1000_coverage.shp — Outline of the extent of the SIS-1000 sidescan survey.
highbackscatter.shp — Areas within the SIS-1000 survey where the sea floor was relatively flat, and the backscatter in general was higher than 55 on the unenhanced sidescan image. Chirp subbottom profiles across these areas mostly show a prolonged, high-amplitude sea floor return.
masswasting.shp — Areas within the SIS-1000 survey where mass-wasting deposits were identified. These deposits were mapped using the sidescan image and the chirp subbottom profiles. The sidescan imagery shows these deposits mostly as having a moderate backscatter surface, and chirp subbottom profiles show an acoustically transparent lens coinciding with these areas.

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