Integration of multibeam bathymetry and sidescan sonar data for geological surveys

Abstract

I. ABSTRACTA geophysical survey conducted off Liverpool, Nova Scotia, Canada in November 1998 collected data using multibeam bathymetric, sidescan sonar, high-resolution subbottom profiler, and acoustic seafloor classification systems. During the survey, multibeam bathymetric and sidescan sonar data were processed on-site and imported into a Geographical Information System for further analysis and display. Shaded relief images derived from the multibeam bathymetric data and sidescan sonar mosaics were combined with data from maps and aerial photographs of the area. These maps and images formed the basis for a preliminary interpretation of geological processes and features on the seabed. Post-processing of the multibeam bathymetric data using newly-developed algorithms improved the resolution of seafloor features and provided acoustic backscatter intensity measurements. These data were used to defme the distribution of coarse and fine-grained sediments and seabed features and to compare and contrast various system resolutions. Seafloor samples and photographs were also taken to provide information for the interpretation of the various acoustic data sets. A variety of seafloor features are presented, using both sidescan sonar and multibeam bathymetric data for illustration.The seafloor is dominated by glacial features deposited during the recession of the last glaciers across the area (ca. 14,000-12,000 years BP). These include a large curvilinear moraine, smaller ribbed moraines and glaciomarine sediment. Bedrock crops out in many areas forming shoals. The glacial features were slightly modified, largely by shore-face processes, during a subsequent rise of post-glacial sea level from a low stand of approximately 65 m below present-day sea level to its present position. During the marine transgression, several coastal sand bodies were deposited at the northern flank of bedrock outcrops. Ribbed or lift-off moraines, which are normally thought to be destroyed in transgressed zones on the inner shelf, dominate the topography of the study area. Their distribution, in depths as shallow as 15 m, suggests that they survived the effects of the marine transgression largely intact. Bottom photographs confirm that the moraines are erosional remnants, armoured by boulders and cobbles. Existing models of marine transgression and sea level history must therefore consider the idea that some glacial features can survive shoreface erosion during marine transgression.

Real-Time Adaptive Control of Multiple Colocated Acoustic Sensors for an Unmanned Underwater Vehicle

“…To overcome this constraint, various techniques are employed to successfully complete a survey of an area of interest with multiple acoustic sensors; the mobilization of separate surveys for each interfering sensor [11], [26], separation of the instruments' operating frequency sufficiently far that they were undetectable from one another [5], [6], and trigger synchronization [1], [2], [27].…”

Terrain-adaptive ping sequencing of UUV integrated multibeam echosounder and sidescan sonar systems

“…Traditionally, compromises were sought to avoid sensor crosstalk by mobilising separate surveys for each of the interfering sensors 15,16 or by separating the operating frequency of the sonar sufficiently far that they are undetectable from one another. 11,17 Temporally separating the transmission-reception cycles of similar frequency sonar provides a more advanced method of crosstalk avoidance.…”

Multi-Sonar Integration and the Advent of Senor Intelligence

“…Accordingly, the provision, and combined analysis, of complementary and comparative datasets affords a more accurate representation of the seafloor, the removal of possible dataset ambiguities and improved data analysis and interpretation (Wright et al, 1996;Evans et al, 1999;Hughes Clarke et al, 1999;Dasarathy, 2000;Fanlin et al, 2003;Duxfield et al, 2004;Nitsche et al, 2004;Shono et al, 2004). Data fusion is the process of taking information from multiple, independent datasets and combining it to extract information not available in single datasets; the combined analysis of contoured bathymetry maps, generated from multibeam echosounders, and the sidescan sonar acoustic reflectivity images permit the geologic interpretation of multibeam bathymetry data to be enhanced by providing an acoustic characterisation of the seafloor from which geologic composition can be inferred, while the bathymetric information improves the representation of the seafloor relief in sidescan imagery by providing the geometric configuration of the seabed (de Moustier et al, 1990;Pouliquen et al, 1999). An integrated interpretation of acoustic datasets is presented by Nitsche et al (Nitsche et al, 2004).…”

“…Others have also attempted to avoid cross-sensor acoustic contamination by separating the operating frequency of the payload sonar sufficiently far that they are undetectable from one another (Pouliquen et al, 1999;Lurton & Le Gac, 2004). As a result, the sonar systems employed are a combination of high-frequency and low-frequency sonar.…”