Removing Tides and Inverse Barometer Effect on DInSAR · By subtracting the phase of 2 SAR images...
Transcript of Removing Tides and Inverse Barometer Effect on DInSAR · By subtracting the phase of 2 SAR images...
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Removing Tides and Inverse Barometer Effect on DInSAR
of Antarctic Ice Shelves
Q. Glaude, S. Berger, C. Amory, F. Pattyn,C. Barbier and A. Orban
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Methodology applied in Dronning Maud Land – Antarctica, but applicable elsewhere
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Displacement from DInSAR
Correction of vertical bias
Results
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SAR is an imaging technique where a spaceborne sensor emits an electromagnetic wave and captures its return
[Copernicus, 2019]
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By subtracting the phase of 2 SAR images taken from different dates and slightly different points of view, we make an interferogram
[TanDEM-X – Copahue volcano, i.e.]
PH
ASE
MA
STER
PH
ASE
SLA
VE
- =
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Many components are influencing the interferogramDInSAR consists in retrieving the phase term related to displacement
𝝋𝒊𝒏𝒕𝒇 = 𝝋𝒐𝒓𝒃+𝝋𝒕𝒐𝒑𝒐+𝝋𝒂𝒕𝒎 +𝝋𝒎𝒗𝒕
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The phase is ambiguous because only known between –π and +π. Phase unwrapping is necessary to retrieve the absolute phase
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Ice shelves are sensitive to variation of the sea level, mostly due to tides and inverse barometer effect (IBE)
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Between two close DInSAR (12 days), we can consider horizontal velocity as stationary, whereas vertical displacement is highly variable
𝑨𝒊 𝒙, 𝒚 = Δ𝒕𝒊𝒅𝒆𝒔𝒊 𝒙, 𝒚 − Δ𝒑𝒓𝒆𝒔𝒔𝒖𝒓𝒆𝒊(𝒙, 𝒚)
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Tides’ amplitudes are computed using the Padman model
[m]
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Similarly, surface atmospheric pressure are computed using the regional atmospheric MAR model
[hPa]
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A double differential interferogram (DDInSAR) consists in subtracting two consecutive interferograms. DDInSAR only accounts for vertical displacements
Roi Baudouin Ice Shelf
Grounded
Floating
10 km
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The DInSAR is corrected by scaling the DDInSAR to the DInSAR vertical bias
Φ𝒅𝒊𝒔𝒑𝒍𝑯𝟏= Φ𝑫𝑰𝒏𝑺𝑨𝑹𝟏 −
𝑨𝟏
𝑨𝟐−𝑨𝟏∙ Φ𝑫𝑫𝑰𝒏𝑺𝑨𝑹
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Results showed a strong decrease of the fringe rate in the grounding zone
Original DInSAR Vertical Bias Corrected DInSAR
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Results showed a strong decrease of the fringe rate in the grounding zone
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In conclusion, we developed a simple algorithm to remove vertical bias from DInSAR for the retrieval of horizontal displacement
Questions ?