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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 
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Data Sources: 
Basemap: Bing Maps Aerial 
Cities & Towns: | www.openstreetmap.org., 
www.mapcruzin.com 
National borders: EuroGeographics 
(epp.eurostat.ec.europa.eu) 
Coordinate System: UTM (WGS 1984) Zone 32N 
  
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® City 
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Nationat border 
Study Area 
  
  
  
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Figure 1: Physical Map of the Study Area “Taubergieflen” in south-west Germany 
A new multilooking approach based on the Gaussian pyramid 
is used in order to suppress noise and to preserve the images 
geometric resolution because multiscale approaches have 
shown a high potential in previous studies (Schmitt, 2009). 
Instead of filtering the image with a constant number of looks 
this method locally adapts the number of looks to the image 
content by selecting the suitable image scale out of the 
Gaussian pyramid. Starting from the coarsest scale, i.e. the 
largest number of looks and hence, the best radiometry, the 
intensity values of the finer scales only are adopted if their 
value deviates significantly from the value with a higher look 
factor. The decision between better radiometric accuracy and 
geometric resolution is made by evaluating a stochastic model 
for the comparison of multilook intensities that is based on the 
beta distribution. Large homogeneous areas are smoothed with 
a large number of looks while fine structures showing 
deterministic scatterers remain unsmoothed. The decision 
pyramid derived from the intensity layer is subsequently 
applied to all available polarimetric layers. 
The resulting layers are geocoded via the TerraSAR-X 
geocoding routines and normalized as described above. As this 
algorithm is not restricted to single-pass acquisitions, it also can 
be used to compare the polarimetric scattering behaviour 
reported by several repeat-pass images. Two image acquisitions 
can be merged by adopting both as independent looks for one 
resulting “mean” image. Beside that they can be merged as well 
by establishing the so-called differential Kennaugh matrix 
(Schmitt, 2012) that comprehends the change in intensity and 
polarimetry in separate layers similar to the Kennaugh matrix 
  
for single pass acquisitions. Even the pyramidal multilooking 
can be used to enhance the information content. The decision 
pyramid is drawn from the total intensity of both images — 
equivalent to the first laser of the “mean” image — and then 
applied to all differential Kennaugh layers. Finally, the 
normalization step converts the changes to the Hyperbolic- 
Tangent-Scaling and enables further conversion to the usual 
unit decibel. 
In summary, a combined description of single- and multi-pass 
acquisitions for all common polarimetric SAR data modes from 
single- via dual- to quad-polarization was developed. 
Additionally, the new multilooking approach guarantees robust 
and reliable radiometric results without losing geometric 
resolution. Consequently, simple thresholding whether by 
empirically or statistically derived thresholds delivers clear and 
smooth classification results. The final value-added product 
displays clearly open water surfaces and flooded vegetation for 
single-pass images and the change in open water and flooded 
vegetation for repeat-pass images. 
1.3  Testsite 
As test area the RAMSAR site “Upper Rhine” in southern 
Germany is chosen which is a wooded flood plain near the river 
Rhine, see Fig. 1. Because of its very small extension and its 
fine structures high resolution SAR data is absolutely required. 
The test site covers large areas of the nature reserve 
"TaubergieBen", which is an important bird area and thus 
belongs to the Natura 2000 network. The wetland itself is 
dominated by freshwater swamp forests and wooded swamps,