Nona IDEAL.
€——
—————— HÀ Lar ot Ur set BJ maire:
Figure 9: Scatter plot of unmodulated phase vis-a-vis phase
unwrapped using quality guided path following
algorithm for a) SNR=0.2, b) SNR=0.3, d) SNR=0.4
and SNR=0.5
The scatter plots of unwrapped phase vis-a-vis the absolute
phase is useful to estimate the number of isolated patches along
any profile. Such scatter plots for quality guided path following
algorithm and weighted multigrid algorithm are shown in
Figures 9 and 10 respectively. The number patches of multigrid
algorithm are always less than that for quality-guided
algorithms. Moreover, all patches also exhibit a positive
correlation, which is not the case for quality-guided path
following algorithm.
a
Laird Uewerrot Whos ale odevol
SNR=04
Verte Phor
p^
p
re NRT a et SNR SN. e
Figure 10: Scatter plot of unmodulated phase vis-a-vis phase
unwrapped using weighted multigrid algorithm for
a) SNR=0.2, b) SNR=0.3, d) SNR=0.4 and
SNR=0.5
Wrapped Phase
30
Figure 11. Simulated interferogram with SNR=0.5 unwrapped
using quality guided algorithm with a perfect
quality map
IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India,2002
Use of appropriate quality images always improves the phase
unwrapping performance. A synthetic quality image derived
from phase noise added during simulation, have found to
improve the performances of both quality guided and multi-
grid unwrapping techniques. Quality guided algorithm when
supplied with phase quality image could unwrap even
interferogram with SNR=0.5 to a single contiguous unwrapped
image (Figure 11). However, in practice such quality maps are
not obtainable from phase coherence images alone.
6. CONCLUSIONS
A number of phase unwrapping algorithms have been evaluated
using simulated SAR interferograms at varying signal-to-noise
(SNR) ratio. At low SNR of 0.1 and 0.2, all unwrapping
algorithms perform equally well. However, at higher SNR
values, weighted multigrid approach is most effective. Quality
guided path following algorithm results next best performance
at cheaper computational cost. Use of phase quality maps
always improves unwrapping performances and yields
acceptable solutions at higher SNR.
Acknowledgements: The author would like to thank Dr.
Shailesh R. Nayak, Group Director, Marine and Water
Resources Group, Space Applications Centre (ISRO),
Ahmedabad, INDIA for supporting this study.
REFERENCES
Akerson, J.J., Yang, Y.E., Hara, Y., Wu, B-I, Kang, J.A., 2000.
Automatic unwrapping algorithms in Synthetic Apérture Radar
(SAR) interferometry. IEICE Tran. Electron., E83-C (12), pp.
1896-1904.
Gens, R., and Genderen, J.L. van, 1996. SAR interferometry-
issues, techniques and applications, International Journal of
Remote Sensing, 17(10), pp. 1803-1835, 1996.
Ghiglia, D.C., and. Pritt, M.D., 1998. Two-dimensional phase
unwrapping : theory, algorithms, and software. Wiley-
Interscience Publication, ISBN 0-471-24935-1, 493p.
Goldstein, R.M., Zebker, H.A., and Werner, C.L., 1988.
Satellite radar interferometry : two-dimersional phase
unwrapping. Radio Science, 23(4), pp. 713-720.
Massonnet, D., 1997. Satellite Radar Interferometry. Scientific
American, 276(2), pp. 32-39.
Pritt, M.D., 1996. Phase unwrapping by means of multigrid
techniques for interferometric SAR. 7EEE Transactions on
Geosciences and Remote Sensing, 34(3), pp. 728-738.
Zebker, H. and Villasenor, J., 1992. Decorrelation in
interferometric radar echoes, IEEE Transactions on
Geosciences and Remote Sensing, 30, 950-959.
KE
A Si
area
tota
ang]
0.1-
higl
Lea:
unit
cont
eva]
effe
effe
of n
sim
moc
and
of t
fron
emp
base
rem
Myr
The
for
base
are
crop
due
LAI
The
real
beer
Rab
Has!
the
appı
199:
