Application for mapping Ice Sheets Akhilesh Mishra Dec 04 2015 Figure 1 1 InSAR review Path length between two signals received by the antennas is a function of the elevation of mapped terrain ID: 461029
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Slide1
InSAR Application for mapping Ice Sheets
Akhilesh Mishra
Dec 04, 2015Slide2
Figure 1: [1]InSAR
review- Path length between two signals received by the antennas is a function of the elevation of mapped terrain
InSAR
Review
where
a = 1
for single-pass
a = 2
for
multipass
a = 2
for single-pass, ping-pong modeSlide3
RADAR Specification
Figure 2: [2]Geometry of the RADAR
Two
Tx channels and 8 Rx channelsBaseline between Tx
is 3.658m, =0Mode of operation -> Ping Pong mode with alternating PRI between two transmitters i.e.
Height above the reference plane ~2500m
Figure 3: [2]Mode of operationSlide4
Ground based
MultiChannel
Coherent Radar Depth Sounder
Center freq
= 150 MHzBW= 30MHzPulse Duration = 10s
Sampling freq = 120MHz
Tx channels = 2Rx channels = 8
Figure 4: [3]Image of the RADARSlide5
Steps for
InSAR
processing for this project -
Pulse Compress the Raw data Bandpass filter, coherently integrate and decimate data in range dimension Bandpass filter, coherently integrate and decimate data in azimuth dimension
SAR process data using Time Domain Back Propagation Steer beam +/- 20 Degrees off nadir
Create Side looking SAR complex imagesCoherence measurements
Image registration Create Interferogram Slide6
Pulse Compression and SAR processing- TDP
Range resolution = 3m
Azimuth resolution = 4m
Figure 5: Small fragment of the data Slide7
Estimation of the bed depth – Reference Height as we move in the along track direction, taken in two way propagation time for applying the
firn
refraction correction
Figure 6: Detection of the reference Height in along track
Figure 7: Dielectric constant profile of ice to model refractionSlide8
Animation for demonstration of beam steering for generating side looking RADAR image
Steering of beam off nadir
Figure 8: Animation for side looking RADAR Slide9
Steering of beam off nadir
Steer the beam to image scene off nadir 300m -900m and avoid the grating lobes
ice = (3e08/sqrt(r)) /fc = 1.13md= 0.857m
Figure 9 : Beam steered to 15o off nadir
Figure 9: [2]Applying Hanning window for steering Slide10
Results of steering the beam off nadir by 15 degrees for two paths
Figure 10: Steered beam for path 1
Figure 11: Steered beam for path2 Slide11
Calculation of the coherence in the two images for registration of images
Figure 12: Absolute power plot of cross track swath 1
Figure 13: Absolute power plot of cross track swath 2Slide12
Figure 14: Absolute power –mean power cross track swath 1
Figure 14: Absolute power –mean power cross track swath 2Slide13
Plots and results of Dr. William Blake
Figure 15: [2]Coherence value with pixel shift of -1.3 for 15
o
off nadir beam Slide14
Figure 16: [2] Constructed
Interferogram
Figure 17: DEMSlide15
References
InSAR
slides,
Dr. Allen INTERFEROMETRIC SYNTHETIC APERTURE RADAR (INSAR) FOR FINE-RESOLUTION BASAL ICE SHEET IMAGING, Dissertation Dr. William BlakeDataProducts and Images from CReSIS