The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
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Netherlands. 
*10 'S * ' * 42 0 
Figure 9. 
Figure 7. Unwrapped phase map of B (masked area with 
coherence less than 0.15) 
Figure 8. Unwrapped phase map of E (masked area with 
coherence less than 0.15) 
Figure 9. Residuals of F after removing the fitted quadratic 
surface 
According to Figure 1, one fringe in azimuth direction and six 
ones in range direction are simulated. After removing the 
simulated fringes in range and azimuth direction from Figure 1 
(bilinear method), few fringes remains, as is shown in Figure 2. 
The unwrapped phase results of Figure 1 and Figure 2 are 
respectively presented in Figure 7 and Figure 8. Evidently, the 
unwrapped phase values are decreased greatly after baseline 
errors are eliminated using bilinear method. The results show 
that the standard deviation (STD) is decreased from 10.9 
radians (Figure 7) to 3.1 radians (Figure 8). In nonlinear method, 
a quadratic function is used to fit the surface of the phase- 
unwrapped map, then the fitted surface is subtracted, as is 
shown in Figure 9. STD is decreased from 10.9(Figure 7) 
radians to 2.8 radians(Figure 9). 
The residuals in Figure 8 and Figure 9 may be caused by 
atmospheric delay errors, unwrapping errors, and uncomplete 
removement of linear fringes. 
4. CONCLUSIONS AND DISCUSSIONS 
According to the results above, we can see that the fringes on 
interferograms caused by baseline errors can be reduced greatly 
with both the bilinear method and nonlinear method. From the 
comparison of STD of Figure 8 and Figure 9, we can find that 
nonlinear method is a little effective than the linear one. 
However, which one is used depends on the patterns of the 
fringes on the interferogram. If the fringes are presented 
nonlinearly, the former is used, or the latter. 
Thanks to ESA for providing SAR images. 
Thanks to DELFT university for providing DORIS software. 
Thanks to JPL for providing SRTM3 DEM data. 
This work is founded by NSFC (40604002 40474002). 
ACKNOWLEDGEMENTS 
REFERENCES 
Hanssen,R.H., 2001. Radar interferometry-Data Interpertation 
and Error Analysis. Kluwer Academic Publishers.