An Automatic Procedure for Ice Drift Estimation in the Fram Strait Region

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An Automatic Procedure for Ice Drift Estimation
in the Fram Strait Region
Morten W. Hansen Nansen Environmental and Remote
Sensing Center NIERSC Summer School (2007)
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Content

• Introduction
• Infrastructure
• Version Control
• Bug and Issue Tracking
• ASAR Archive
• Sea Ice Monitoring
• Ice Drift Procedure
• Conclusions

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Introduction 1

• Current Satellite Services on the Web
• Harmful Algal Bloom Monitoring (HAB)
• Synergetic Use of ASAR-MERIS Data for Coastal
  Monitoring (SARIS)
• Envisat ASAR Archive
• Planned Service
• Automatic Ice Drift Estimation and Forecasting

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Introduction 2

• Automatic downloading, processing and display of
  satellite data three parts
• Download of satellite data and other auxiliary
  data from various ftp or http servers
• Processing combining data from different
  sources, generating derived products, map
  projection, mosaic creation etc. and
• Display of the derived products (mainly images)
  on various web pages.
• Need for shared responsibility in maintaining and
  developing the code

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Infrastructure 1

• Subversion
• An Open Source Version Control System
  (Unix/Linux)
• Easy to Use
• Easy to Maintain
• Upload code
• Locally svn checkout file///Data4/sat/svnSatRep
  o sat
• Remotely svn checkout svnssh//nansen.nersc.no/
  Data4/sat/svnSatRepo sat
• Check in code
• svn ci m some comments about the changes
• Update code
• svn update
• Everyone can work on the same files at the same
  time (minor) problems only occur if two
  programmers change the same lines of code!

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Infrastructure 2

• Trac
• An Open Source Bug and Issue Tracking System
• Suitable as a Project Management Tool
• Clarify project goals
• Set project timeline and milestones
• Interface to Subversion
• Integrated Wiki
• Discuss issues
• Manage users
• Easy to Use
• Browse source and history
• Register new tasks
• Register finished tasks
• Share problem solving
• Not so Easy to Maintain

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ASAR Archive

• Select area
• View latest ASAR Acquisitions
• Classify Images

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Ice Drift Monitoring

• Security of navigation
• Climatic impact
• Sunlight absorption
• Thermohaline circulation
• Geological impact
• Biosphere influence

Microwave measurements (passive AND active) are
independent of solar illumination and
meteorological conditions, thus suitable for
monitoring sea ice!
Aqua AMSR-E Ice Extent 2007.08.22
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Ice Drift Procedure
Envisat ASAR (2)
Envisat ASAR (1)

• Ice Mask from AMSR-E
• ASAR Images from ESA Rolling Archive
• Pattern Recognition Algorithm (Kloster et al.,
  1992)
• Drift Vectors from pairs of SAR images
• Correlation between 0 and 1 to indicate vector
  quality
• Database
• Vectors from all investigated images
• Ice Drift Map
• Manual Verification
• New Drift Map

Aqua AMSR-E March 2006
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Results
Average speed 1 km/day Max speed 62
km/day Size of map 5000 650 km2
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Summary Conclusions

• Subversion and Trac are essential tools when
  working with complex systems and many developers
• Ice drift by SAR imagery in combination with
  Passive Microwave
• Need improved algorithm
• Problem with length of arrows in the maps
• Small scale variations cause unrealistic disorder
  in the resulting maps
• Should consider to only estimate drift for images
  with a constant time difference and use averages,
  thus filtering out small scale variations
• Results need further verification against models
  and other measurements

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References

• K. Kloster, H. Flesche, O.M. Johannesen Ice
  Motion from Airborne SAR and Satellite Imagery,
  Adv. Space Res. 1992