Detailed Lecture Schedules

USCHC Coastal Multibeam Training Course

• REVIEW AND CONCEPTS
  • Introduction - Historical Background
  • System Concept and Course Overview
  • Electrical Engineering Terms and Concepts
  • Geology and Geotechnical Terms and Concepts
  • Acoustic Terms and Concepts
  • Spatial Referencing Terms and Concepts

• SWATH SONAR TECHNOLOGY
  • Single Beam and Boom Systems
  • Bathymetric Sidescan Sonar Methods
  • Multibeam Sonar Methods
  • Sonar Imaging
  • Bottom Detection Methods
  • Graphical Representation of Swath Sonar Concepts

• COMPLEMENTARY SENSOR INFORMATION
  • Ship Reference Frame
  • Horizontal Positioning - Requirements and Methods
  • Orientation - Requirements and Methods
  • Vertical Positioning - Requirements and Methods
  • Sound Speed in the Water Column

• CASE STUDIES
  • Refraction - Implementation and Limitations
  • Positioning - Case Studies
  • Orientation - Error Sources and Effect
  • Error Estimation in Swath Sounding

• OPERATIONAL ISSUES
  • Survey Design and Planning
  • Field Calibration - The Patch Test
  • Quality Control - Error Recognition and Identification
  • Overview of Available Swath Sonar Systems
  • Field Demonstrations

• THEMATIC DATA
  • Seafloor Acoustic Backscatter Theory
  • Normal Incidence Classification Methods
  • Swath Sonar Classification Methods
  • Acoustic Backscatter Data Interpretation

• DATA PROCESSING
  • Overview of Processing Pipeline
  • Data Structures
  • Navigational Filtering
  • Bathymetric Data Cleaning - Interactive Methods
  • Bathymetric Data Cleaning - Automated Methods
  • Refraction Residuals - Methods for their Correction
  • Integration of Seamless Vertical Datums

• DATA PRODUCTS AND USES
  • DTM Generation, Methods, and Pitfalls
  • Sonar Backscatter Mosaicing
  • Visualisation
  • Multiparameter Chart Products
  • Data Management - Archiving Issues
  • ECDIS and the Role of High Density Data

Historical overview of swath sonar evolution. Definition of common terminology. Statement of modern requirements.

System Concept and Course Overview

Presentation of course aims and approach. Detailed course outline, description, and timetable. Field operations planning.

Electrical Engineering Terms and Concepts

Simple harmonic signal, probability density functions, frequency domain representation, Fourier transforms, convolution - correlation, CW pulse, and FM sweep.

Geology and Geotechnical Terms and Concepts

Marine sediment nomenclature, evolution of offshore morphology, sediment physical properties - acoustic wave interactions, bulk properties and elastic constants, elastic wave types, acoustic impedance, typical values.

Acoustic Terms and Concepts

Geometry of measurement, aperture concepts, spatial resolution, sonar equation, practical sonar frequencies.

Spatial Referencing Terms and Concepts

Coordinate systems, datums, measures of performance.

Single beam systems - transducers, beam patterns, propagation and losses, resolution. Why do we get echoes? Sweep systems.

Bathymetric Sidescan Sonar Methods

Geometry, resolution, along and across track, slant range correction, 2-row sidescan systems.

Multibeam Sonar Methods

Beam forming, beam steering, FFT beam forming, array geometries.

Sonar Imaging

Swath data outputs, backscatter intensity data reduction, registration for bathymetric sidescans, FFT beamformers, interlaced beam envelopes, and single sample per beam.

Bottom Detection Methods

Fundamentals, weighted mean time, differential phase zero crossing, bearing deviation indicator.

Graphical Representation of Swath Sonar Concepts

3-D interactive graphical representations of beam forming, beam steering, side-lobe suppression, and bottom interaction. Review of concepts presented to this point.

Integration of sonar ouptuts with complementary sensor information. The role of the ship's reference frame. Multi sensor relative location and orientation. Time based multi-sensor integration. Active vs. passive attitude compensation.

Horizontal Positioning - Requirements and Methods

Swath sonar requirements, horizontal positioning methods, result derivation, trends.

Orientation - Requirements and Methods

Coordinate systems, three-dimensional rotations, accuracy requirements, attitude measurement methods.

Vertical Positioning - Requirements and Methods

Requirements, problems, conventional methods and their limitations. What is OTF? OTF applications and limitations. Trends.

Sound Speed in the Water Column

Theory of refraction in a heterogeneous medium. Review of scale of problem in oceanic, coastal, fluvial, and lacustrine environments. Methods for measuring sound speed in water, and available accuracies. Theory of ray tracing in layered mediums, either with discrete stratification or constant gradients.

Method of implementing ray tracing in swath sounding solutions. Computational efficiencies. Assumptions inherent in implementation. Real examples of the application showing common scale of errors due to both temporal and spatial variations in the water mass. Methods for minimising these problems.

Positioning - Case Studies

Example applications of OTF GPS to high density swath sounding data. Use in tidal reduction. Use in heave and squat estimation. Taking advantage of high accuracy positioning to complement the detailed spatial resolution of the sonar.

Orientation - Error Sources and Effect

Potential sources of error in orientation sensors. The appearance of these errors in survey data. Methods for the isolation and quantification of these errors. Methods for avoiding these error sources.

Error Estimation in Swath Sounding

Estimating the total propagated error in the final sounding solution based on knowledge of individual error characteristics of each component of the integrated survey system. Examples of application to existing installations and comparison with real data.

Critical issues to consider in the design and planning of a swath sonar survey. Coverage, overlap, line orientation, cross lines, survey speeds, resolution, accuracies.

Field Calibration - The Patch Test

Explanation of field procedures for the recognition and quantification of static time delays and sensor misalignments. Choice of appropriate seabed geometries and line orientation for isolating specific static offsets.

Quality Control - Error Recognition and Identification

Methods for recognition and identification of dynamic error sources from acquired data. Use of specific graphical displays to recognise characteristic signatures of common dynamic error types including: time delays, misalignment, scaling, refraction, long period heave.

Overview of Available Swath Sonar Systems

A review of currently available swath sonar systems. Methods for transmission, reception, beam forming, beam spacing, bottom detection are contrasted. Real examples used as a review of acoustic principles.

Field Demonstrations

A hands-on introduction to a variety of representative swath sonars through the use of launch based demonstrations. Installation, integration, calibration, operation, and processing applied in the field.

Overview of theory of acoustic seabed interaction. Reflection, scattering, surface roughness, volume scattering. Critical seabed physical properties and their values for common seabed types.

Normal Incidence Classification Methods

Methods for seabed classification using the return from a normal incidence sonar. Applied to single broad beam systems and multi-transducer systems. Discussion of first return methods vs. first and multiple methods.

Swath Sonar Classification Methods

Methods of seabed classification using backscattered data from swath sonar systems. Textural methods, Echo PDF methods and use of the backscattered angular response. The need to compensate for seabed topography, imaging geometry, and ray path distortions.

Acoustic Backscatter Data Interpretation

Recognising and interpreting features and artifacts in swath sonar backscatter data. The appearance of wrecks of different scales using hull-mounted systems. A direct comparison of high-speed hull-mounted sonars vs. low-speed deep-towed sonars.

Review of data processing stream appropriate for high- density swath sonar data (both bathymetry and backscatter). Identification of major problem areas and difference from conventional single beam processing.

Data Structures

An overview of digital data representations including data types and data structures. Appropriate use of dynamic range of different data types given the range and resolution of archived data. Issues of inter-platform portability (byte ordering, byte alignment).

Navigational Filtering

Methods for cleaning navigational data, taking advantage of the high density of the swath bathymetry and the tight constraints on likely vehicle path indicated by complementary attitude data.

Bathymetric Data Cleaning - Interactive Methods

Graphical interactive methods for presenting high-density swath bathymetric data for the purpose of outlier identification and rejection. Integration of complementary data in the form of attitude, backscatter, and neighbouring swath information.

Bathymetric Data Cleaning - Automated Methods

Automated statistical methods for the identification of outliers within high density bathymetric data sets. A comparison of 4 published approaches.

Refraction Residuals - Methods for their Correction

Methods for the quantification and correction of systematic residual errors in swath bathymetric data due to imperfect knowledge of the water column. Coping with temporal and spatial variations in water masses. Assumptions inherent in water mass models. Potential for the use of checklines as a means of quantifying residual errors and their correction.

Integration of Seamless Vertical Datums

Assessment of the feasibility of introducing seamless vertical datums making use of ellipsoids as the ultimate data reference rather than local chart datums or geoid models.

Examines the methods for bathymetric terrain model derivation. Advantages and disadvantages in representing high density data as DTMs. Compromises inherent in derived raster representations.

Sonar Backscatter Mosaicing

Methodology for spatially mapping variations in seabed backscattered data. Coping with variations in insonified footprint, grazing angle, illumination azimuth, and beam pattern residuals. Trade-offs between honouring imaging geometry and computational efficiency.

Visualisation

Review of visualisation principles, including 3-D projections, sun-illumination. Using multiple degrees of freedom to represent different seabed parameters (depth, slope, backscatter, uncertainty, etc.). Application to high density swath sonar data. Practical use of cable and pipeline engineering operations.

Multiparameter Chart Products

Presentation of map-like products that can be derived from high density swath-sonar systems. Bottom morphology, bottom sediment type, bottom slope, bottom roughness information. Methods for viewing and interpreting these products.

Data Management - Archiving Issues

Assessment of the scale of the data archiving problem. Identification of the type of information that needs to be easily accessible for spatial and temporal searches.

ECDIS and the Role of High Density Data

Presenting an overview of electonic charts and the role that high density bathymetric data is likely to play in the evolution of this product. Discussion of integration of real-time elevation information.