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IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
Important steps in SAR interferometry procedure are: selection 
of data sets; co-registration of the images; generation of 
interferogram; phase unwrapping; height calculation DEM 
p 
  
5. Ice and glacier movements: Measurements of ice and 
glacier movements have been reported by Jouglin et al. 
(1998). 
  
Figure 10. Aseismic creep along the Hayward fault, California. Based on SAR 
interferogram from images acquired in June 1992 and September 1997, aseismic creep of 
2-3 cm with right-lateral sense of movement has been inferred. (Black-and-white printed 
from colour image). (After Buergmann et al. 2000) (Source: photojournal.jpl.nasa.gov) 
generation and geocoding. 
Data used includes aerial systems such as AIRSAR (JPL), 
CCRS - SAR (Canada) etc., and various other aerial InSAR 
systems. Out of the space-borne missions, data from ERS-1, -2, 
JERS-1, Radarsat and SRTM have been used. 
4.3 Applications 
The InSAR-derived DEMs have found utility in a wide range of 
geoscientific applications 
l. Earthquake studies: SAR interferograms from earthquakes 
are well reported in the literature. A number of examples 
have been published showing use of InSAR technique for 
mapping fault lines on the Earth's surface and measuring 
fault displacements (e.g. Massonnet et al., 1993). 
N 
Aseismic creep: exhibited by Hayward Fault, California, is 
an interesting example of measuring subtle ground 
deformations using InSAR (Fig 10). A displacement of 2-3 
cm with right-lateral sense could be measured (Buergmann 
et al., 2000). 
3. Land subsidence: Measurement of urban subsidences are 
reported by many workers, e.g. in Napoli by Tesauro et al. 
(2000). Further, using DInSAR, Mouelic et al. (2002) 
show measurement of uplift of ground by 1.3cm +/- 0.3 cm 
in Paris, the uplift being apparently related to the rise in 
ground water piezometric level at the end of underground 
construction work. 
4. Landslides: Use of InSAR technique for monitoring of 
landslides in Alpine terrain with movements of a few mm 
/year to a few cm / year is reported by Nagler et al. (2002). 
6. Volcano monitoring: From DInSAR, monitoring of 
volcanic hazards is a highly promising application area. 
Around an active volcano, often surface inflation and flank 
deformation takes place due to lava emplacement, before 
the active volcanic eruption occurs. These subtie surface 
changes in volcano morphology can be monitored through 
DInSAR (e.g. Lu et al., 2002). For example, at the Three 
Sisters Volcanic region (USA), the USGS detected uplift 
of ground surface over an area of 15-20 km diameter, 
believed to be a result of the intrusion of a small volume of 
magma at depth (Fig. 11). 
4.4 Limitations 
A number of factors affect interferometric SAR data processing 
(e.g. Gens, 1998). Precise determination of baseline is very 
important to know the viewing geometry. Atmosphere is 
important as heterogeneous atmosphere leads to refraction 
affecting interferograms. Physical changes in the character of 
the terrain surface (e.g. vegetation growth etc.) during the 
interval of two SAR passes (temporal decorrelation) may occur 
affecting InSAR output quality. Normal baseline distance 
beyond a certain limit may also preclude some specific high- 
resolution applications. 
5. CONCLUDING REMARKS 
From the above it can be concluded that the remote sensing 
techniques are being increasingly applied to collect quantitative 
data on various geological aspects, such as the chemistry of 
minerals, temperature of volcanic vents, lava flows, coal fires, 
and on ground deformation accompanying earthquakes, 
volcanic activity, creep etc. 
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