|Coastal and Marine Geology Program|
GLORIA sidescan sonar data were collected during a survey conducted in the Gulf of Mexico during 1985 and 1986. The collected data were recorded digitally and processed to correct for geometric distortions and signal noise. The processed data swaths were later geographically registered and combined to create 16 sonar mosaics for a 2 degree by 2 degree. The GLORIA sidescan sonar mosaic shown below in panel 1 is a subset of one of those quadrangles. More detailed background regarding the U.S. Exclusive Economic Zone (EEZ) GLORIA Mapping Program may be found here while specific information regarding the GLORIA Gulf of Mexico data may be found here.
The GLORIA imagery shown here is a subset of the available datasets and covers the Sigsbee Escarpment area located in the Gulf of Mexico between 90 and 91 degrees west and 26.5 and 27.5 degrees north.
NOS gridded SeaBeam Bathymetry
In 1989 and 1992, the Ocean Mapping Section of the National Ocean Service's (NOS) Coast and Geodetic Survey (C&GS) produced several gridded data sets of SeaBeam multibeam bathymetry. The produced data sets covered an area 1/2 degree latitude by 1 degree of longitude at 250 meter grid spacing. The bathymetry image shown below in panel 2 was generated by combining two of the NOS gridded data sets, Researcher Basin and Mitchell Basin, to produce an image representing a 1 degree by 1 degree area.
Depths within this area range from approximately 1300 to 3100 meters. However, the 16-bit bathymetry data values were compressed to 8-bit for presentation here as GIF files.
Color-encoded GLORIA sidescan image
The image shown in panel 3 below illustrates the benefit of combining the two individual datasets (GLORIA and SeaBeam). By merging the GLORIA sidescan sonar mosaic with the SeaBeam bathymetry, features in the GLORIA image may be more easily identified with regard to their relationship with the seafloor topography.
Color Encoded Shaded Relief and Perspective Images
The NOS gridded SeaBeam bathymetry was used to generate a shaded relief image of the area. The shaded relief image was then encoded with the bathymetry to generate color intensity, saturation, and hue images. When those images are combined in RGB planes, they create an image such as the one shown above.
By combining the shaded relief image with the NOS bathymetry, seafloor features, such as Hydrographers Basin and Green Knoll, become more easily identified.
Three fly-by movies of the Sigsbee Escarpment generated from the imagefiles shown above are included and may be viewed with an 'MPEG' viewer. The image shown to the left is one of the individual frames contained in the movie and is an exaggerated perspective of the Sigsbee Escarpment and Green Knoll.
The animations included here were generated using the PCI Remote Sensing Corporation's (www.pcigeomatics.com) program FLY!. By overlaying selected imagery on the available bathymetric grid generated from the NOS SeaBeam bathymetry, the user is able to generate near real-time fly-by's through the imagery. The FLY! program allows the user the ability to select speed and direction, elevation above the scene, and viewing direction.
To generate the individual fly-by's, the flight path was saved to allow the same path to be passed over with different sets of combined imagery. As the flight path was replayed for the individual data sets, the individual scenes or frames were saved as 'TIFF' files. When the fly-by sequence was completed, the individual 'TIFF' files were then encoded into an 'MPEG' file to allow playback through any 'MPEG' viewer.
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