## 5 Data Processing and Experimental Results: SAR Mode
### First Results
Exceptions to the above considerations are represented by some isolated man-made targets which are present in the scene (see, the targets highlighted with the yellow ellipses in Figures 10 and 13). In this case indeed the average phase difference between the HH and VV channels is nearly \(\pi\), see Figure 12b, and the even-bounce component (the blueish pixels in Figure 13) represents the dominant contribution to the scattering mechanism. Figure 12: Relevant to the SAR data-set collected by the flight track considered in Figure 10. Correlation coefficients between polarimetric channels: Amplitudes (**a**) and phases (**b**). To show the interferometric potentialities of this SAR system, we consider three repeat pass acquisitions carried out over the TS4 site. Few minutes elapsed between the different acquisitions. Application of the processing chain depicted in Figure 9 has led to the generation of twelve focused SLC, one for each track and polarimetric channel. Table 3 reports main data processing parameters. As an example, Figure 14 shows, in the ground range-azimuth grid, the amplitude of the corresponding MLC relevant to the HH channel. The observed scene has an extension of about 14 Km in azimuth and 3 Km in (ground) range. Figure 15 shows the SAR image of the top panel of Figure 14 in geographic grid and superimposed to a Google Earth orthophoto. For all the interferometric data pairs achievable with the different polarimetric channels, we have carried out a first interferometric analysis, by using the processing parameters listed in Table 4. In particular, Figure 16 shows the interferometric coherence relevant to the VV channels, which turned out to be on average the highest one with respect to that achievable with the other combinations of polarimetric channels. As can be seen, in most of the observed area the obtained coherence is quite good. Coherence losses are however observed in near range and in some well confined azimuth strips, due to the spatial decorrelation effects induced by the large spatial baselines generated by the severe track deviations of the helicopter during the radar acquisitions. This is confirmed by the height of ambiguity maps reported in Figure 17 and relevant to the same data pairs considered in Figure 16. As can be seen, in the low coherence regions of Figure 16 the height of ambiguity reported in Figure 17 reaches very low (absolute) values. Note in particular, that the color scale in Figure 17 is set between (\(-15\) m, \(15\) m) to highlight that trajectories are crossing, causing the interferometric baseline to go to 0. Accordingly, at some locations the height of ambiguity becomes infinite (hence all the saturated areas), and then returns in the interval (\(-15\), \(15\)) with opposite sign. Figure 14: SAR results relevant to three repeat pass flight tracks on TS4. HH channel, SAR-Low mode: Amplitude of the SAR MLCs in ground range-azimuth grid. Acquisition date: 15 May 2018. Mean flight velocity: 50 m/sec. Mean flight altitude: 1600 m. Mean terrain height: 730 m. From the top to the bottom panel the acquisition start time is: 14:21:32, 14:38:31, 14:58:13. Figure 15: As the top panel of Figure 10 but represented in geographic grid and superimposed to a Google Earth orthophoto. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline Azimuth spacing & 4 m & Ground range spacing & 6.25 m \\ Azimuth resolution & 15 m & Ground range resolution & 15 m \\ \hline \hline \end{tabular}
\end{table} 
Table 4: SAR data processing parameters relevant to the InSAR results collected in Figures 16–18. Figure 16: Relevant to the repeat pass interferometric SAR data-set collected by the flight tracks considered in Figure 14. Coherence maps relevant to the VV channels. Figure 17: Height of ambiguity maps relevant to the data pairs considered in Figure 16.  
Figure 18: Interferograms relevant to the data pairs considered in Figures 16 and 17.