This tutorial will review the key aspects of the design of synthetic aperture sonar (SAS) systems for high resolution seabed imaging. After a quick overview of the expected benefits and main features of SAS, the design of the transmitter and receiver arrays will be discussed, with emphasis on the mitigation of spatial aliasing with multi-element receiver arrays, wideband operation and extension to interferometric SAS for estimating the seabed bathymetry.

Next the most difficult issue in SAS, which is the micronavigation problem, i.e. that of estimating the unwanted platform motions with the required sub-wavelength accuracy, will be addressed in detail. The emphasis will be on methods which have proved their value at sea, which combine inertial navigation systems (INS) with data-driven methods based on the Displaced Phase Centre Antenna (DPCA) technique. The topics covered will include the theory of spatial backscatter coherence, the derivation of ping to ping motion estimates using time delay estimation theory, including the use of bandwidth for phase unwrapping and the appropriate range-dependent near field corrections to arrive at unbiased estimates, the establishment of the Cramer Rao lower bounds for motion estimation which demonstrate the need for fusion with an INS to achieve full performance. The geometrical relationship between the DPCA and INS projection frames, which is necessary for accurate fusion, will be established and shown to depend also on the local seabed slope. The estimation of this slope with interferometric sonar will be discussed.

Furthermore the impact of the environment, and in particular of the multipath structure in large range to water depth ratios will be discussed. Multipath will be shown to degrade the quality of the SAS imagery as well as adversely impact the accuracy of interferometric estimates including DPCA. Means to mitigate multipath operation by management of the vertical transmission and reception beams will be discussed, showing experimental results which point to some of the limitations of existing sonar performance prediction tools.

Finally different design tradeoffs between computational efficiency and robustness for micronavigated SAS imaging algorithms will be discussed and an example of a real-time implementation suited for operation on-board an autonomous underwater vehicle will be described.

Bio Marc Pinto

Marc Pinto was born in Wellington, India in 1960. He graduated from the Ecole Nationale des Ponts et Chaussées, Paris (France) in 1983. From 1985 to 1989 and 1989 to 1993 he worked as a research engineer for Thomson-CSF, specializing in the development of finite element techniques for solving non-linear magnetostatics to support the modeling of the magnetic recording process. In 1991, he received the Ph.D. degree in Solid State Physics from the University of Paris, Orsay. In 1993 he joined Thomson-Sintra ASM (now Thales Underwater Systems) as Head of the Signal Processing Group, specializing in research into advanced MCM and airborne ASW sonar. In 1997 he joined the NATO Saclant Undersea Research Center, La Spezia, Italy as principal scientist. He was appointed Head of the Mine Countermeasures Group, in the Signal and Systems Division in 1998 and held this position until the group was dissolved in 2000. From 2000 to 2004 he conducted, as project leader, research into synthetic aperture sonar systems for hunting proud and buried mines. In 2004 he was appointed Head of the Expeditionary MCM and Port Protection Department where he presently oversees the research into AUV-based minehunting, electronic mine countermeasures and harbour defence.

AUV Application Basics is a short course that provides an overview of AUV technology and operations. The objective is to provide an overview of what AUV systems can provide and the best practices for their use. The class is targeted at scientists interested in using AUVs for oceanographic applications. The attendee will gain basic understanding of AUV types, technologies, and navigation techniques, including discussion of the comparative strengths of AUVs and alternative methods of data collection. The attendee will also be provided an understanding of trade-offs in AUV operations, including power estimation, endurance considerations, and mission structure to acquire the desired data sets.

Key points are illustrated by applications and results from the Monterey Bay Aquarium Research Institute's (MBARI) Dorado AUV and other AUV operations. Topics include: Basic AUV technology, AUV at-sea Operation, Payload Considerations, Mission Planning, Upper and Mid-Water AUV missions, Benthic and Mapping AUV missions, Data Collection and Reduction, AUV Integration into Sampling Networks, and a look at coming AUV advances.Intended Participants:

This class is intended for scientists interested in applying AUVs to particular problems, persons interested in AUV applications and the impact of AUV technology, and graduates in oceanographic fields seeking a broader understanding about the application of AUV platforms.

Bio: W.J. Kirkwood

Bill is currently the Associate Director of Engineering at the Monterey Bay Aquarium Research Institute (MBARI) located in Monterey Bay, California. Bill has a BS in Mechanical Engineering and a MS in Computer Science which he has applied to controls and automation of electromechanical systems and robotics since 1978. Bill has been with MBARI for 15 years as a lead mechanical engineer and program manager developing the Tiburon remotely operated vehicle. Bill also performed as program manager and lead engineer developing the Dorado class autonomous underwater vehicles at MBARI. Bill's current efforts are focused on precision and/or automated in situ instrumentation and laser Raman spectroscopy for the deep ocean science.

Acoustic seabed classification is the organization of the sea floor and shallow subsurface sediment into discrete classes based on information in the echoes. Geoacoustic sediment properties such as grain size and porosity are not available from acoustic backscatter alone, but the survey area can be segmented into regions of similar acoustic character. Systematically exploiting details in backscatter is the basis of acoustic segmentation.

This tutorial presents theory and applications of image-based acoustic classification, from the early papers through to recent applications. The acoustic principles of classifying with echoes from single beams at normal incidence are presented first, since they relate to the principles of image classification. Near nadir, the amplitudes and shapes of sounder echoes are rich in sediment information. Away from vertical incidence, echoes carry sediment information in their amplitudes and their noise characteristics, but not in their shapes. Echoes from imaging sonars, with their wide horizontal beamwidths, become rasters in sonar images, so noise in these echoes becomes image texture. Macro-roughness such as sand waves and changes in sediment also contribute to texture. Image amplitude and texture are both heavily influenced by sediment type and are exploited for segmentation.

Sonar calibration is not necessary for image-based acoustic classification. Image amplitudes are made consistent throughout a survey, but remain in relative, not absolute, units. Since calibrating imaging sonars is challenging, the ability to use systems that need only be consistent offers cost-effective practical classification for military and civil purposes.Topics in this tutorial include:

• Quality control, suppressing system artifacts.
• Compensating images for beam patterns and grazing angle effects.
• Features that capture amplitude and texture characteristics.
• Classification with amplitude: backscatter, backscatter vs. grazing angle.
• Classification with texture: Pace, Haralick, fractal, wavelet.
• Differences between classifying multibeam and sidescan images: resolution, using bathymetric
  data for compensation, benefits of images stitched together from backscatter in beams.
• Supervised classification, training sets.
• Unsupervised classification, PCA, manual and automated clustering.
• Using non-acoustic data to relate acoustic classes to sediment geoacoustic properties.
• Categorical interpolation.
• Maps with acoustic classes in similarity colours.

The techniques presented in this tutorial are wide ranging, and do not concentrate on a selected technical approach. As time allows, hands-on experience with classification software suites will reinforce the tutorial material. Participants are invited to bring their own laptops for this part of the tutorial, and would be able to continue classifying data sets after the session has ended.

Through this combination of theory and experience, participants in this tutorial can expect to gain a thorough understanding of principles and practice of image-based sediment classification.

Bio: Dr. Jon Preston

Dr. Jon Preston (PhD, University of British Columbia) is Senior Scientist at Quester Tangent Corporation, Sidney, BC, and an adjunct professor at the University of Victoria. In his seven years at QTC he has lead the development of software suites for rigorous statistical classification of multibeam and sidescan images, interpolation and visualization of acoustic classes, and automated objective clustering through simulated annealing.

This half-day workshop will focus on the "do's and don'ts" of preparing for, conducting and then dealing with the data collected during an airborne hyperspectral survey. The session will cover:

• background to the technology
• planning an airborne survey (design and layout of flight lines, things to avoid)
• execution of the survey (type of aircraft to use, when to fly)
• data pre-processing (geocorrection, atmospheric correction)
• overview of data analysis
  

The session leader has been involved in airborne hyperspectral surveys for seventeen years and has organized and conducted airborne surveys in more than twenty-five countries on four continents. The session will include plenty of real-life examples from many of these projects.

Bio:Herb Ripley

Herb has been trained in geography and remote sensing/geomatics and has spent his entire career with Atlantic Canadian firms. Herb has comprehensive experience in all aspects of aerial photography and airborne remote sensing data collection acquired in over 25 years of project work. This experience includes projects conducted both nationally and internationally. Herb's world recognized casi project experience includes numerous applications but in particular he has considerable experience on coastal projects including mapping invasive species, coral reef surveys, mapping benthic habitats and mapping near-shore vegetation. Herb has been principal author and co-author on numerous technical publications During his career Herb has been very active in industry develop mental activities and has held executive positions with the Nova Scotia Oceans Initiative, the Champlain Institute, the Alliance for Marine Remote Sensing, the Geomatics Industry Association of Canada and the Geomatics Association of Nova Scotia. As a recognition of his professional standing, several years ago Herb was appointed a Fellow of the Remote Sensing Society (U.K.).