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image pair, several processing steps have to be performed. One of 
the current challenges is to bring the techniques to a level where 
DEM generation can be performed on an operational basis. Multi 
pass interferometry is affected by the atmospheric effects. Spatial 
and temporal changes due to the 20% of relative humidity produce 
an error of 10 cm in deformation. Moreover, for the image pairs 
with inappropriate baseline the error introduced to the topographic 
maps is almost 100 m. 
Distinction between SAR imaging and the optical systems are 
more profound than the ability of SAR to operate in conditions that 
would cause optical instruments to fail. There are basic differences 
in the physical principles dominating the two approaches. Optical 
sensors record the intensity of radiation beamed from the sun and 
reflected from the features. The intensity of the detected light 
characterizes each element of the resulting image or pixel. SAR 
antenna illuminates its target with coherent radiation. Since the 
crests and troughs of the emitted electromagnetic wave follow a 
regular sinusoidal pattern, both the intensity and the phase of 
returned waves can be measured. 
InSAR has some similarities to stereo-optical imaging in that two 
images of the common area, viewed from different angles, are 
appropriately combined to extract the topographic information. 
The main difference between interferometry and stereo imaging is 
the way to obtain topography from stereo-optical images. Distance 
information is inherent in SAR data that enables the automatic 
generation of topography through interferometry. In other words 
DEMs can be generated by SAR interferometry with greater 
automation and less errors than optical techniques. Moreover, 
using DInSAR surface deformations can be measured accurately. 
(Tarikhi, 2009) 
4. USING INSAR TECHNIQUE FOR AQUATIC 
BODIES; A NEW APPLICATION 
InSAR techniques are developing rapidly and increasingly. Its civil 
applications include oceanography (ocean waves, ocean currents, 
wind, circulation, bathymetry), hydrology, (Kanevsky, 2009) 
glaciology, seismology, volcanology, land subsidence and uplift 
studies, change detection, coastal zones monitoring, forestry, 
cartography, geology, soil science, agriculture, environmental and 
hazard monitoring, and archaeology, (Henderson, et al. 1998) 
while its non-civilian applications are reconnaissance, surveillance 
and targeting, treaty verification and nonproliferation, navigation 
and guidance, foliage and ground penetration, moving target 
detection, and target detection and recognition. The domain and 
extent of the applications of this technique is still rapidly 
developing and expanding. In course of the years since 1994, 
studies and verifications by the Microwave Remote Sensing Group 
that is currently based at the Alborz Space Center (former 
Mahdasht Satellite Receiving Station) of Iran’s space agency has 
been carried out continuously on developing the applications of 
InSAR technique leading to good and valuable achievements. The 
studies include verifying and investigation of the variety of 
phenomena namely Izmit quake of August 1999, Bam quake of 
December 2003, L'Aquila quake of April 2009, Haiti earthquake 
of January 2010 and Chile earthquake of February 2010. 
4.1 Data and Methodology 
In continuation ofthe exploratory work of using Synthetic 
Aperture Radar Interferometry (InSAR) technique on aquatic 
bodies in different locations of the above-mentioned study sites the 
one-and-half-a-year project C1P.8242 under the ESA (European 
Space Agency) affiliated European Space Research Institute 
(ESRIN) was started in February 2011 by the Microwave Remote 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
Sensing Group at the Mahdasht Satellite Receiving Station. 
ESRIN has secured the needed data for the project. The 
background of this study and exploratory work goes far back to 
October 2010 when the author observed that using SAR 
Interferometry technique for aquatic bodies with the temporal 
baseline of maximum 16 seconds for image pairs could show 
considerable results enabling us to estimate the stagger speed of 
water bodies in coastal areas, the direction of sea surface motion in 
larger extent, the change in the height of the sea surface in the 
satellite sensor’s look direction and consequently the sea surface 
height change trend, wave pattern and the sea surface disturbance 
and whether the water motion is bulk and smooth or otherwise. 
Figure 3 illustrates the idea and geometry of the coverage of two 
successive SLC images. (Kanevsky, 2009) 
4.1.1 Study Areas and data used: The method has been 
examined for three different global areas in tropical zone, southern 
and northern hemisphere. In the tropical zone we have studied 47 
Envisat SLC SAR images of Haiti, Dominican Republic, North 
Atlantic Ocean, Golfe de la Gonave, Caribbean Sea and Lago 
Enriquillo acquired in 2010. For southern hemisphere 37 Envisat 
SLC SAR images of Western Chile and South Pacific Ocean 
acquired in 2010 have been examined. In the northern hemisphere 
1860 Envisat SLC SAR images of Western Turkey including 
Black and Mediterranean Seas coast areas and inland lakes 
acquired in 2002-2010 have been studied, however empirical field 
checkups is still necessary and the job will also be continued for 
examining other sites around the world for which the relevant data 
is available. For this application of SAR Interferometry the title of 
Liqui-InSAR is proposed that refers to the use of SAR 
interferometry technique for liquid bodies in general that is 
distinguishable from the SAR Interferometry of solid bodies for 
which the expression of Solid-InSAR is proposed and that deals 
with the non-fluid features like soil, sand, vegetation, rocks, 
snow and other cryo-spheric phenomena. 
4.1.2 Methodology: Common image processing and 
combination techniques used in SAR Interferometry as depicted in 
Figure 1 was applied benefiting the IMAGINE-InSAR and IDIOT 
to examine and assess the applicability of the technique for the 
aquatic bodies. Successful use of SAR Interferometry technique 
for aquatic bodies requires comparison of the SLC image pairs 
with very short temporal baselines. For Envisat SLCI data the 
temporal baseline should be ranging between 8 and 16 seconds. It 
is because of the technology that is used by synthetic aperture 
radar system. Normally the image acquisition period for each SLCI 
is 16 seconds. During this period of time the SAR system transmits 
a microwave beam in the form of a pulse towards the target and 
then records the reflections bounced back. Sending pulses and 
recording the corresponding reflections is repeated regularly but 
because of the rotation of Earth and satellite movement on a 
predefined and definite orbit the successive forwarded pulses hit 
different locations on the land surface which are situated on the 
strip that is satellite’s track on the land surface in the direction of 
satellite movement. In practice there is a time overlap between two 
successive imaging processes that leads to the overlap of the 
scenes imaged successively. This overlap normally differs between 
15 to 60 percent for ERS and Envisat SAR data. This short time 
baseline is useful for ideally generating DEMs when it is shorter 
than 10 seconds, and that the parallel component of the virtual 
baseline decreases, since the parallel baseline component plays key 
role in generating the interferograms. It is actually a way for 
producing accurate DEMs benefiting three-pass SAR 
Interferometry. However it is not as precise as the procedure used 
by NASA’s Shuttle Radar Topography Mission (SRTM) which