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Ice Sheet Motion

Ice Sheet Motion

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Ice Sheet Motion

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Presentation Transcript

  1. Ice Sheet Motion Speckle tracking

  2. InSAR Feature Retracking Day 1 100 m Day 24 Day 1 Day 24 Day 1 Day 24 10 m 10 m Velocity measurement techniques Speckle Retracking

  3. Speckle Geometry

  4. Range direction only

  5. Preprocessing

  6. Doppler Overlap (See if you can use the image data to compute doppler spectra)

  7. Velocity Processing

  8. Azimuth Corrections • Azimuth pixel spacing goes as prf as well as orbit height, terrain elevation, look angle and latitude. Consequently two slightly different orbits will have slightly different azimuth spacings given approximately by For a purely vertical separation, corresponding to about 14 m in height, the azimuth Displacement will change about 3 parts in 10^6. There will be an accumulating Error such that after about 500 km, the azimuth will be incorrect by a measurable .3 pixels.

  9. Comparisons

  10. Coherence Streaks An early incorrect idea

  11. Ionospheric Streaks • For C-band Radarsat, A SAR footprint is illuminated for about 0.5 sec. The satellite travels about 3.5 km. • If the integrated electron density changes along the line of sight, while the footprint is illuminated, then the phase history built from about 600 pulses will be corrupted • The consequence is incorrect azimuth placement. • The effect is smaller in the range direction.

  12. Streaks • Idea tested by • Comparing streak density with ionospheric activity • Simulations using a phase screen • Relationships to streak density and magnetic poles

  13. Option 3 – only ascending descending range products. Option 1 – azimuth offset, range phase; azimuth offset, range offsets; ascending descending range;

  14. Calibrating Phase Islands in the Absence of Local Control

  15. Phase and Range Offset

  16. Phase reconciliation

  17. Information from Wrapped Phase

  18. Plug Vr into Vf and differentiate along flow direction We assume that several terms are small: change in look direction is small; changes in flow directions are small for large glaciers over 0-30 km, Large scale strain rates not effected by surface slope.

  19. Calculated Strain Rates