Data selection proces The first question that needs to b

the highest possible spatial res provide the opportunity to work w

R

100

splacement map based on the interferometric pairs 14.08.09 m of vertical change.

ferograms

interferograms is an approach that works w ccessful phase unwrapping (GAMMA2008). It is b a complex number with the complex conjugate o between the arguments of the two complex num

results in the scaling of the wrapped phase w

of ‘artificially’ modifying the spatial baseline by grams.

s study for the generation of a differential inte 0 (= Int.1) and interferogram 12.08.10/ 05.05 ines were estimated for - 158 m and -0.43 m re t in an effective baseline of -37.29 m (-195 – ( - 15 am now contains the differential phase compon

phase information of the second pair. Consequ the differential interferogram is much lesser therefore the combined interferogram will be m

ss

be addressed is which satellite system should be olution for radar data was desired. Additionally with new datasets to explore their information con

Remote Sensing Data

9/ 25.08.09 and 14.08.09/

without a DEM and, ased on the idea that of a second complex mbers, and the phase with the same integer

scaling the wrapped

erferogram based on .10 (= Int.2). In this espectively, therefore 58m) = - 511 m). The nent of the first pair, uently the information than the containing much better suited to

e used. In this case, y, the system should ntent. The selection of

Remote Sensing Data

101

the recently launched German TerraSAR-X satellite was therefore a very quick process, since not only very good quality data could be expected from its sensor, but it also offered a lot of unexplored possibilities. Its images seemed to be perfect for this methodical research that also includes some new applications.

TerraSAR-X

Launched on June 15th 2007, the German TerraSAR-X satellite acquires new high-quality X-band radar images with a spatial resolution of up to 1 m of the entire planet, whilst circling Earth in a polar orbit at 514 km altitude. Its major purpose is the acquisition of high-accuracy global SAR data for scientific and commercial use, which is why its mission is the result of a public-private partnership between the German Federal Ministry of Education and Research, the German Areospace Centre (DLR) and Astrium GmbH. TerraSAR-X is supposed to operate for 5.5 years. The X-band sensor operates at a frequency of 9.65 GHz which equals a wavelength of around 3 cm (DLR, 2010). The repeat period is 11 days, but due to the ascending and descending swath overlay, a 2.5 day revisit time is possible (Infoterra GmbH, 2010). Images can be acquired in either single, dual or quad polarization, and in three operational imaging modes: SpotLight (resolution 1 m; footprint 10 x 5 km), StripMap (resolution 3 m; footprint 30 x 50 km) or ScanSAR (resolution 18 m; footprint 100 x 150 km) illustrated in Figure 7.24.

Figure 7.24: The different acquisition modes ScanSAR, StripMap and Spotlight from the TerraSAR-X satellite (modified after Infoterra GmbH 2011)

Unique features of TerraSAR-X are its high spatial resolution (up to 1 m) independent of weather conditions and illumination, and its high geometric accuracy. A further advantage of this satellite is its partner satellite TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement), in space since June 21th 2010. It is almost identical to TerraSAR-X, and together they form the first bistatic SAR mission by flying in a closely controlled formation with a distance of 250 – 500 m (DLR 2011). The cooperation of the two spacecraft will serve to generate new quality DEMs of the world, ‘along-track interferometry (e.g. measurement of ocean currents) and new bi-static applications (e.g. polarimetric SAR interferometry)’ (DLR 2011).

Although the launch of TanDEM-X was unfortunately too late to use its data for the purpose of this study, it might be beneficial if continuing studies in this research field and this test site are desired.

ScanSAR Mode

StripMap Mode

Spotlight Mode 514 km

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