# Ten Years of Experience with Scientific TerraSAR-X Data Utilization
## 3 Results
### Analysis of the Scientific Publications based on TerraSAR-X Data  
Analogous to the analysis of the 1636 TerraSAR-X proposals, a keyword scan was performed in Scopus to all titles, author and index keywords of the 2850 publications referring to TerraSAR-X. In total, 116 keywords were selected and grouped in a way so that they represent the same six fields of  
Figure 12: Geographic and quantitative distribution of scientific areas of interest observed by TerraSAR-X between 2007 and 2017, the color indicates the number of acquisitions per \(1^{\circ}\times 1^{\circ}\) tile. research as for the proposals. The publications were then assigned to the research area (sphere) which best represents the keyword search (see also Section 2.1). Figure 13 shows the corresponding results. A noticeably high percentage of papers deal with methodological and technical issues (36 percent), followed by a large number of papers in the hydrosphere group (22 percent). The geosphere (13 percent) represents the second largest geoscientific group. Whereas the fractions of anthroposphere (11 percent) and biosphere (10 percent) are very similar, the cryosphere (8 percent) shows a relative small number of publications. It should be noted that there are overlaps between the different research fields, particularly between hydrosphere and cryosphere as well as anthroposphere and geosphere. Snow and glaciers are at the center of attention in cryosphere research but at the same time they also play an important role in the hydrological cycle, e.g., as water source and reservoir. The observations of volcanos and earthquakes improve the understanding of the tectonically active areas of the Earth in terms of location and areal extent, dynamics and intensity. Many of those areas are densely populated and, thus, relevant for anthropogenic research as well. Figure 14 presents the number of TerraSAR-X related publications from 2003 to 2016. Prior to the launch of the TerraSAR-X satellite in 2007, only a small number of papers about preparatory work were published. Three years after the launch, a significant increase of publication activities can be noticed, with an increase from 153 publications in 2010 to 510 in 2016. The number of articles continuously increased in all research fields until 2015. This trend continues for the anthroposphere, hydrosphere and geosphere. The number of publications related to cryosphere issues remains fairly constant, while those related to biosphere and methods decreased between 2015 and 2016. Figure 14: Accumulation of TerraSAR-X related research papers for thematic areas between 2003 and 2016. Figure 13: Histogram of TerraSAR-X related fields of research, expressed in percent based on the analysis of 2850 publications. Analysis of the scientific literature suggests that the dominant use of high-resolution SAR data is the derivation of surface movements. 1044 publications address this topic, 834 (29 percent of all TerraSAR-X related publications) of them deal with deformation and displacement of the solid land surface including glacier flow and 210 with movements of the ocean surface like currents, wave and wind fields. 720 articles (25 percent) used SAR interferometry including its different processing variants like PSInSAR or SAR-tomography. Feature tracking techniques were applied in 214 publications (8 percent), in 72 cases in combination with SAR interferometry. SAR polarimetry is the focus of 256 papers (9 percent). Change detection is carried out in 8 percent of the published articles and proposals. The analysis further reveals monitoring as one of the main applications, referred to in 425 articles from the keyword search. Mostly monitoring comes along with the detection and understanding of changes of the land cover composition and extent. A regular observation of the area of interest is required, and longer time series are employed to analyze seasonal and multi-year dynamics. A significant number of publications (237 papers) deal with changes and change detection.