NWPHYS007 — Use underwater acoustics to map waterways

Elements & performance criteria

Performance evidence

• adjusting acoustic parameters for optimum performance during sounding operations
• analysing and reporting echo sounder returns through differentiation between return signals
• analysing and reporting on the following:  problems or artefacts in on-line data due to inappropriate configuration or changing environmental parameters  side scan sonar records considering target characteristics, system configuration, potential sources of noise and distortion  sources of error and angle uncertainty depending on acoustic parameter configuration
• analysing sounding data and identifying the marine floor type using backscatter analysis
• analysing the water column to identify features
• applying quality control procedures to data acquisition and on-line processing
• calculating and reporting on components contributing to uncertainty in derived ranges
• creating sound speed profiles from water column measurements and describing the effect on the acoustic ray path
• detailing sources of noise and the impact of noise on operation of acoustic systems
• reviewing acoustic results and reporting to relevant personnel
• selecting appropriate range, scale, frequency and pulse repetition rate for marine floor surface return and assessment of sediment layer in relation to spatial resolution, bottom penetration and depth of water
• setting up, deploying and operating all of the following types of underwater sonar systems including:  side scan  single beam  swath echo sounders

Knowledge evidence

• acoustic wave behaviour with reference to physical properties of the water column
• active sonar equation including:  causes of propagation loss in relation to water properties together with characteristics of the sea floor and targets  noise level and directivity  sound source
• characteristics of acoustic units, intensities and sound levels
• combining sources of uncertainty
• echo sounders including:  bottom detection principles  components of a single beam echo sounder  full echo envelope returns  operation of single beam echo sounders  split beam and dual beam echo sounders  sub-bottom profiling systems
• plane and spherical waves including:  amplitude  frequency  wavelength
• principles and geometry of multibeam and interferometric (phase measurement) sonar systems
• principles, components, geometry and deployment of side scan sonar systems
• quality control procedures for hydrographic surveys
• refraction and the path of sound rays through the water column
• side scan including:  images and sources of distortion  sonar backscatter and floor reflection
• speed of sound in relation to water properties and profile in the water column
• swath echo sounders systems including:  amplitude and phase bottom detection  backscatter and seabed classification  beam forming and beam steering  gain, power and pulse length  hull and pole mounting of transducers considering platform motion  integration of components including:  attitude compensation  networking  sensor offsets  time stamping  optimisation of environmental factors for measurement and target detection  surface and water column sound speed monitoring  system parameters including:  bandwidth  detection  gain  pulse length  pulse repetition rate  range resolution  spatial resolution  threshold  transducer parameters impacting beam characteristics, elements and arrays  validation and calibration for hydrographic surveys  variations in beam spacing and footprint size

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