Application potential in oceanography, offshore industry and navy

1
Flow field mapping with AUVsPhD project, Oyvind
T. Odegaard

• Measurement uncertainty modeling

• Post-processing and visualization methods and
  tools

• System requirements and survey design

• Application potential in oceanography, offshore
  industry and navy

2
Flow field mapping with AUVsMeasurement
uncertainty modeling

• Aim
• Interactive model
• Inputs Sensor type and configuration, Navigation
  system characteristics, survey architecture,
  environmental parameters
• Output Velocity uncertainty vector
• To be used for survey system selection/design and
  operation planning

• Navigation uncertainty modeling approach
• Modeled using NavLab (Navigation Laboratory)
  developed by FFI in the HUGIN AUV programme.
• Approach
• Specifying an AUV mission in three dimensions
• For each mission, specifying
• A collection of navigation sensors
• The short- and long term error characteristics of
  each sensor
• The time-varying availability of each sensor
  (e.g. DVL only at seabed, GPS only at surface)
• Having the NavLab simulator generate an
  artificial set of sensor readings from the
  specified sensors
• Having the NavLab estimator process the
  artificial data set
• Recording the uncertainty of the AUV velocity and
  orientation as estimated by NavLab. (The
  theoretical uncertainty attainable if the sensor
  suite behaves exactly as modeled)

• Uncertainty budget has two main elements
• Current sensor uncertainty
• Depends on model, make and configuration relative
  to environmental factors. Acoustic Doppler
  current profilers (ADCPs) typical choice.
• AUV navigation uncertainty.
• Depends on several sub-systems. Complex to model

3
AUV current measurementsPost-processing and
Visualization Software

• Post-processing challenges
• A variety of different but interrelated types of
  data are sampled
• ADCP data (vector and scalar)
• CTD data (scalar)
• Platform/instrument system state variables
  (vector and scalar)
• All data referenced to space
• Additional geodata required for interpretation
• All data referenced to time
• The measured process (flow field) may
  significantly evolve during the survey
• The 3D motion of the AUV requires a spatially
  more unconstrained processing and visualization
  regime than the software tools used for
  ship-mounted and stationary sensors

• ANCOR (ADCP Navigation Correction)
• Written and run in MATLAB
• Earth-references ADCPCTD data with AUV nav data
• Enables post-synchronization of data sets
• Performs quality checks and calculates statistics
• Offers temporal and spatial smoothing
• Provides interactive visualization features
  intended to facilitate perception of time-space
  relationships between the various data categories