# Ten Years of Experience with Scientific TerraSAR-X Data Utilization
## 3 Results
### Proposal Analysis Overview
#### 3.1.5 Hydrosphere  
The hydrosphere is the second largest group, accounting for 18 percent of all proposals. Here, research questions referring to oceans, coastal areas, limnology, soil moisture and overarching the hydrological cycle in general are addressed (see Figure 8).  
Wind field and sea state retrieval is the major application, with 53 percent of the hydrosphere-related proposals. The latter mainly benefits from the higher spatial resolution which enables the derivation of shorter ocean waves with the shorter wavelength X-band system [140; 141]. High radiometric performance is essential for wind field retrieval [142; 143]. The high precision is utilized for offshore wind farming support [144]. The relatively low orbit of TerraSAR-X supports an improved observation of features on the sea surface compared to other L- and C-band sensors. Extreme weather conditions like storm observations and rogue waves generation [145] are investigated as well as the wind and wave interactions with ice [146].  
Figure 7: Thematic fields of geosphere related TerraSAR-X proposals, sorted by frequency addressing small- and large-scale surface deformations caused by the Earth crust’s dynamic (technics), volcanic activities, landslides and soil mapping including erosion.  
The mapping of inland waters is focus of 45 percent of the proposals. Seasonal changes [147; 148] are monitored and the available amount of water is estimated [149]. Special attention is paid to water management [150].  
A third of the proposals deal with coastal applications. Tidal flats [151; 152], salt marshes [153] and submarine ground water discharge [154] are monitored. Intertidal bedform shifts are investigated and the impact on sediments and benthic macrofauna [155] is assessed. For coastal protection purposes, oil spill detection and monitoring is performed [156; 157; 158].  
Mapping and monitoring of soil moisture in arid and semi-arid environment is another key application (15 percent of the proposals) [159; 160]. Here, soil moisture is important for water resources and irrigation management, but also for runoff estimations and land surface degradation processes.  
Another 14 percent are engaged in the identification and observation of vessels. This includes not only ships, but oil platforms and other sea based infrastructure as well. Ship surveillance is performed to increase security [161] and safety [162]. Apart from the ship identification and classification, ship heading and velocity estimation [163] is dealt with. Also, near real time services have been developed [164].  
Furthermore, ocean currents are of interest for 10 percent of the proposals. Here, the capability of Along Track Interferometry (ATI) is evaluated [165]. Variations in the backscatter intensity are likewise utilized, e.g., for the investigation of bottom topography-induced current front in a tidal channel [166].  
The bathymetry, especially of coastal areas, is of interest for 5 percent of the proposals. The bottom topography is derived by observing the wave behavior in shallow waters [167] and by evaluating the temporal correlation between the backscatter intensity and the water level [168].  
Only 20 percent of the proposals mention interferometric measurement techniques. 6 percent of these intend to apply along-track interferometry, while 19 percent request polarimetric data.