Understanding the surface morphology and sediment in the deep water environment is important for construction of platforms and pipelines, estimating for potential geological hazards, and development of physical oceanography and sediment transport models. As bathymetry is mainly a surficial reflection of subsurface allochthonous salt in the Gulf of Mexico, a detailed bathymetry can help us understand the deep structure. This study uses multibeam system bathymetry data, rejects erroneous data points, and examines different interpolation methods. The error points are removed from the georeferenced data based on an algorithm usually used during the survey (Hertihy et al., 1992). To generate optimum resolution of the bathymetry data, different spatial interpolation methods are examined. Universal kriging with a linear model (UkI) seems to be the best choice for the Sea Beam data in this study.
The GLORIA II sidescan sonar image released by National Geophysical Data Center (NGDC) is prone to the uncertainty of pixel locations and ambiguity of artifacts versus true backscattenng. This study corrects these errors and examines location inaccuracy. The reprocessed GLORIA II image has a location accuracy of about 400 m. In a 50 m gridded bat hymetry and sonar image, the spatial uncertainty is about 8 pixels. The possibility of reducing the noisy near nadir pixels is discussed. In a single sonograph strip, the processed image shows significant improvement. When these sonographs are georeferenced on a plane earth, spatial interpolation is used to readjust the aspect-ratio. The resultant image seems fuzzier than the original image but contains fewer artifacts.
Ground truth samples are used to examine sediment accumulation rates. A change of the accumulation ratio through time for two cores suggests episodic sediment inputs. The ground truth data are also used to model the acoustic energy attenuation rate. The result show that the energy is more than 3dB down or has lost more than 50% of its incident energy at a depth of 500cm below the seafloor.
Four different Geographic Information System (GIS) packages are used to take advantage of their build-in functionality and compliment their deficiencies. Bathymetry data, properties derived from bathymetry data, sidescan sonar imagery, ground truth data, and other support geophysical data are integrated to give a geological interpretation of the canyon. The ability of automated and interactive mapping through the Internet is briefly discussed at the end of Chapter IV.