obtained elevation data on a near-global scale to generate the most 
complete high-resolution digital topographic database of Earth 
using a specially modified radar system that flew onboard the 
Space Shuttle Endeavour during an 11-day mission in February 
2000. 
position II 
  
  
    
    
position I 
common area of the 
successive images coverage 
image source: Pervir Tarikhi 
Figure 3: Coverage area of two successive SLC images 
4.2 How the Technique Works 
Using InSAR technique for the aquatic bodies in coastal areas and 
inland lakes looks promising when it is applied for the image pairs 
with temporal baselines shorter than 16 seconds. It is easily 
explained by the basic theory of the interferometry of optical 
surfaces using the interference of light which, under specific 
conditions, can produce visual patterns disclosing surface 
"topography" down to a fraction of a wavelength. Although it is a 
general discussion, it fits the case of the surface of aquatic bodies 
that in some sense act as the optical media. In general, the 
interferometer is an optical device combining two wave-fronts - 
one reference, perfect, and the other produced by the test surface - 
in order to produce the interference pattern making test surface 
visible quite well below the sub-wavelength size level. The 
simplest and traditional interferometer consists of two surfaces 
positioned at a slight angle one to another (Figure 
4). 
  
LIGHT Li 
Figure 4: Interference pattern formation for straight 
surfaces (image source: http://www.telescope- 
optics.net/testing optical quality.htm#prevent) 
As light passes through the two pieces of glass 
that is a transparent medium (refraction is 
negligible at actual angles for principal 
rays/wave-front), at every section where the gap 
increases by about 1/2 wave, waves tend to 
interfere destructively, forming dark lines, so 
  
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 
I . ss i 
MONOCHROMATIC EX ist position 
  
called interference fringes. Consequently the shape of lines 
depends directly on the surface shape. If both surfaces are flat, then 
the interference lines are straight (Figure 4). If one or both surfaces 
are curved, the dark lines of destructive light interference will be of 
circular form (Figure 5) provided the surface possesses rotational 
symmetry. Surface irregularities will cause deviation of the 
interference lines from straight, curved or circular line form and 
can be measured to a small fraction of a wavelength. 
Since conic aberrations cause different form of wave-front 
deformations, they also show distinctly different interferometric 
patterns (and since wave-front deformation relative to a reference 
sphere varies with focus point within the aberrated focus zone, 
interferogram patterns will also be different for best focus in 
comparison to other focus points for each particular aberration). 
The fringe spacing in a single-pass interferometer corresponds to 
M2 differential on the surface, or À on the wave-front; in a double- 
pass interferometer fringe spacing corresponds to half as large 
surface/wave-front differential. The same explanation applies for 
the moving surface layers of aquatic bodies that practically act as 
the optical/transparent surfaces when beamed by radar waves. 
(Sacek, 2006) 
  
  
Reference sur ece ^7 
Figure 5: Interference pattern formation for curved surfaces (image source: 
http://www.telescope-optics.net/testing optical quality.htmZprevent) 
S. RESULTS 
In Figure 6 a diagram of the application of Liqui-InSAR technique 
is given. Two samples of the results for the Western Haiti and 
Western Turkey coastal zones are given below (Figure 7, Figure 8 
and Figure 9) however the comprehensive collection of the 
products 
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Figure 6: Diagram clarifying Liqui-InSAR technique 
    
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