Conventional Side Scan Sonar Systems are proven tools for search and qualitative seafloor analysis, however they are not appropriate for seafloor mapping. EG&G has combined microprocessor technology and the side scan sonar technique in their SMS960 Seafloor Mapping System which gives a real time plan view map of the seafloor. The system is described with particular emphasis on quantitative data analysis.
Seafloor maping has application in hydrography, channel dredging, geologic surveys, pipeline surveys, construction siting, hazard surveys, and search. Mapping with conventional side scan is difficult because: the data presentation is severely distorted, data collection is inconsistent, and data storage does not allow for reprocessing. To explain the cause of these problems, the general side scan principles are reviewed.
The Seafloor Mapping System applies automatic spatial corrections for slant range and speed to give high resolution, plan view graphic images, of the seafloor. Automatic amplitude corrections are also applied such that the darkness of the image relates directly to the backscattering strength of the seafloor material. Multiple image strips from the system may be combined to form mosaics of entire areas of interest. Minimally processed sonar data are recorded on digital tape along with reference data to accommodate retrieval and/or reprocessing by playback, through the SMS. Examples of corrected and uncorrected data are used to demonstrate the system capability. Mosaics of large seafloor areas are also presented.
While the-system represents a quantum improvement in side scan technology it is only the beginning. Now digital image process techniques can be applied, by processing the SMS tapes on Large scale computers.
High resolution maps of land areas are generated from aerial photographs and radar images. The original data is later corrected for sensor distortions by photo grammetric techniques. Analogous detailed seafloor maps can now be generated by the Model SMS960 Seafloor Mapping System developed by EG&G Environmental Equipment Division. It utilizes a side scan sonar sensor, the 8080 microprocessor, and a unique multi-stylus digital printer to collect data, correct for distortions, and generate high resolution plan view maps in real time. Accurate geomorphological maps of the seafloor find application in:
The extent of the various seafloor materials may be overlayed on hydrographic charts by direct scaling of 8M8 maps. In addition, the maps may be used to optimize bathymetric survey line spacing, reducing required sea time.
The edges of a channel may be accurately determined in addition to detecting and locating any hazardous anomalies within the channel.
Classification of seafloor materials is possible based on the darkness and texture of the image. Sediment transport may be determined by subsequent surveys.
Large areas may be viewed to determine the optimum pipeline or cable route. After laying, the precise route may be determined;
Hazardous platform locations may be accurately determined and avoided.
Ship wrecks, downed aircraft, and lost objects, may be displayed with high resolution (1/4 meter) and the exact location of all parts determined.
