# Ten Years of Experience with Scientific TerraSAR-X Data Utilization
## 3 Results
### Proposal Analysis Overview
#### 3.1.6 Methods and Techniques  
A small share of the proposals--13 percent--addresses methodological and technical developments rather than specific application fields. Figure 9 shows the major techniques where further developments were proposed.  
Figure 8: Thematic fields of hydrosphere-related TerraSAR-X proposals, sorted by frequency addressing oceanographic applications, coastal zones, inland waters, soil moisture and the identifications and observation of ships and ship traffic.  
Close to a third (32 percent) of the proposals target improvements of techniques for measuring surface movements like persistent scatterer interferometry [169], distributed scatterer interferometry [170] and subpixel offset techniques [171]. The common goal is to overcome the limitations of the differential interferometry like geometric and temporal decorrelation, atmospheric artifacts and the one-dimensional line of sight sensitivity. Along track interferometry combines data sets acquired during a single overflight and enable the observation of internal waves [172] and tidal energy resource assessment [173].  
The goal of 27 percent of the proposals is to assess the polarimetric information in TerraSAR-X data. Some examples are the derivation of polarimetric information for mapping purposes [174], the improvement of the image segmentation of high-resolution polarimetric data [175; 176], novel classification approaches [177] or texture tracking in polarimetric SAR data [178].  
The development of techniques for the identification of changes is focus of 13 percent of the methods related TerraSAR-X proposals. The high spatial resolution and the SAR image speckle cause significant backscatter intensity variations even within a single object on ground. In order to simplify and optimize change detection, techniques such as image segmentation [179; 180] and similarity cross tests based on polarimetric features [181] are applied.  
SAR tomography is another development of the persistent scatterer interferometry that utilizes multi-incidence angle observations of the same targets on ground. It thereby enables the 3d-localization and motion of scattering objects [182; 183]. The 3D coordinates can also be derived by radargranmetry [184; 185]. Here, an image set acquired from at least two different positions in space is processed similar to the elevation model generation from optical data with a stereo-like view. The so called SAR imaging geodesy enables solid Earth tide measurements [186] by utilizing the very high spatial resolution and range measurement accuracy.  
In summary, SAR interferometry is the main application for TerraSAR-X data. Fifty-two percent of all proposals investigate various kinds of surface movements. Different differential interferometric measurement and feature tracking techniques are employed. Twenty-seven percent request single polarized TerraSAR-X data for mapping purposes. Nineteenpercent ask for dual- and quad-polarized data. The remaining 2 percent are interested in SAR experiments and the development of new modes.  
Figure 9: Thematic fields of methodological and technical research related TerraSAR-X proposals, sorted by frequency addressing differential SAR interferometry including its further developments such as PSInSAR, polarimetry, automated detection of changes, SAR tomography, and radargrammetry for 3d mapping.