134 
value of freezing bulge is 5 mm, and maximum value of 
thawing subsidence is 25mm in this area during 2004 to 2006. 
Figure 6. Distribution of PS candidates around Qinghai-Tibet 
railway and highway overlaid on SAR image. 
6. CONCLUSIONS 
In this paper, we process 13 ASAR images and obtain 16 
interfergrams with different temporal and spatial baseline. The 
characteristics of coherence for different surface objects are 
analyzed at Beiluhe area in the Qinghai-Tibetan plateau. Due to 
the difference of their structure and dielectric properties, ground 
objects show widely variety on their coherence coefficients. 
The permafrost’s thawing and freezing influence the ground 
objects’ pattern and structure, and lead to change of ground 
objects’ coherence. Between the active periods of frozen ground, 
coherence reduces obviously and is mush lower than in the 
stable period. With temperature rising and beginning of process 
of thawing, alpine aim’s coherence reduces quickly. The ground 
objects’ coherence pass two active processes are lower than 
after one active process, and are full decorrelation after whole 
thawing/fazing circle procedure in the study area. 
Figure 7. Deformation history of PS during 2004 to 2006 
around Qinghai-Tibet railway. The master image is acquired in 
Jan. 27, 2005 
The Qinghai-Tibetan railway and highway keep high coherence 
under the condition of long spatial. The image pixels, 
representing the railway and highway, are coherent over almost 
all the observation. So these pixels can be chosen as permanent 
scatters for deformation sequence analyzing of frozen ground. 
The deformation of railway roadbed, detected by Permanent 
Scatters Interferometry, mainly appears in the way of thawing 
subsidence from May to November every year with 25 mm 
maximum subsidence in the two years. 
REFERENCES 
Bamler, R. & Hard P., 1998. Synthetic aperture radar 
interferometry. Inverse Problems, 14(4), pp. Rl-54. 
Berardino, P., Fomaro, G., Lanari, R. & Sansosti, E., 2002. A 
new algorithm for surface deformation .monitoring based on 
small baseline differential SAR Interferograms. IEEE Tram. 
Geosci Remote Sensing, 40(11), pp. 2375-2383. 
Bu'rgmann R., Hilley, G., Ferretti, A. & Novali F., 2006. 
Resolving vertical tectonics in the San Francisco Bay Area 
from permanent scatterer InSAR and GPS analysis. Geology, 
34(3), pp. 221-224. 
Colesanti, C., Ferretti, A., Novali, F., Prati, C., & Rocca, F., 
2003. SAR monitoring of progressive and seasonal ground 
deformation using the permanent scatterers technique. IEEE 
Trans. Geosci. Remote Sensing, 41(7), pp. 1685-1701. 
Ferretti, A., Prati, C., & Rocca, F., 2000. Nonlinear subsidence 
rate estimation using permanent scatterers in differential SAR 
interferometry. IEEE Trans. Geosci. Remote Sensing, 38(5),pp. 
2202-2212. 
Li, Z., Li, X.W., Liu, Y., 2004. Detecting the displacement field 
of thaw settlement by means of SAR Interferometery. J. Glaci. 
Geocry, 26(4), pp. 389-396. 
Ma W., Shi C., Wu Q., et al., 2006. Monitoring study on 
technology of the cooling roadbed in permafrost region of 
Qinghai-Tibet plateau. Cold Regions Science and Technology, 
44, pp. 1-11. 
Nan, Z.T., Li, S. & Liu,Y., 2002. Mean annual ground 
temperature distribution on the Tibetan Plateau. J. Glaci. 
Geocry, 24(2), pp. 142-148. 
Zebker, H.A., Rosen, P., Goldstein, R.M., Gabriel, A. & 
Werner, C.L., 1994. On the derivation of coseismic 
displacement fields using differential radar interferometry: The 
Landers earthquake. J. Geophys. Res., 99, pp. 19617-19634. 
Zhao, L., G. Cheng, S. Li, et al., 2000. Process of freezing and 
thawing in active layer in Wudaoliang permafrost region of the 
Tibetan-Qinghai Plateau. Chinese Sci. Bui. 45(11), pp. 1205- 
1211. 
ACKNOWLEDGEMENT 
This work was supported by funds from NSFC and CAS under 
grants 40671140 and kzcx2-yw-301. The EnviSat ASAR data 
were provided by ESA through the Category-1 ID: 1406. The 
authors wish to thank Dr. Bert Kampes for providing Doris 
software.