## 4 Results
### Sabratha and Metaponto Case Studies
#### 4.2.2 Results  
At the archaeological site of Sabratha, the processing and interpretation of remote sensing data focused on an area characterized by lesser-known archaeological features. They are composed of linear micro-relief, visible from optical images by means of shadow marks, attributable to shallow remains (walls, foundation) close to the Sabratha amphitheater. The COSMO-SkyMed Spotlight scene acquired on 12.12.2012 provides a stunningly detailed map of the features (see Figures 11b and 12a-d) thanks to the high resolution of the image and the effect of double bounce in backscattering as shown in Figure 13 (see also [42]). The same micro-relief could be observed from a multi-temporal image set available from Google Earth shown in Figure 11c-f. However, compared with the Spotlight image, the visibility of micro-relief is reduced in three of them (October 2009, 20 August 2011, 26 May 2012 in Figure 11c-e)) and similar in one (16 February 2013, in Figure 11f). A significant improvement of the Spotlight scene in terms of the visibility of archaeological micro-relief was achieved using adaptive and statistical filtering (Figure 12). In particular, the best results were obtained by calculating the sum of squares of the Lee filtering products (Figure 12d), which reduced the noise in the surroundings of the features, enhancing the micro-reliefs of archaeological interest. Figure 11: Detecting unknown archaeological features in Sabratha (Libya). **(a)** detail of an area characterized by the presence of micro-relief and traces of archaeological interest; **(b)** The archaeological features are clearly visible from the COSMO-SkyMed Spotlight image acquired on 12 December 2012, at 1m geometric resolution, in ascending orbit, with an angle of incidence of 27.320\({}^{\circ}\) and HH polarization; **(c–f)** Google Earth scenes on 8 October 2009, 20 August 2011, 26 May 2012 and 16 February 2013. The red boxes indicate the area with micro-relief (or shadow marks) whose visibility is less than in the Spotlight image in three of them (October 2009, 20 August 2011, 26 May 2012) and similar in one of them (16 February 2013). In Metapontum, a number of features related to palaeochannels, palaeoriverbeds, ancient roads and land divisions were investigated. They are very clearly visible from the available COSMO-SkyMed Spotlight image shown in Figure 14. For the sake of brevity, we shall discuss only the results obtained for two palaeochannels (A and B) and a road in the ancient urban fabric dating back to Greek colonization. Figure 12: Sabratha (Libya): Enhancement of the COSMO-SkyMed Spotlight scene in the red box in Figure 12. In detail: (**a**) raw data; (**b**) Sum\({}^{\wedge}\)2; (**c**) enhanced Lee filter; (**d**) SUM\({}^{\wedge}\)2 of the enhanced Lee filter result. Figure 13: Model of the response of elementary scattering mechanisms to the presence of archaeological microrelief and traces. In Figure 15, a multi-temporal image set available from Google Earth centers on a palaeochannel named A. The four scenes cover a temporal interval from May to September in different years (2004, 2006, 2013). In all four scenes, the palaeochannel feature, linked to variations in moisture content and vegetation cover lacks the typical curvilinear shape thus making it difficult to identify and map. Conversely, the axis is clearer from the Spotlight scene in Figure 16a and its enhanced version in Figure 16b. Figure 14: Metapontum (Southern Italy): a number of archaeological and palaeoenvinmental features are visible from the COSMO-SkyMed Spotlight image acquired on 14 November 2011 at 1 m geometric resolution, in a descending orbit, with an angle of incidence of 41.5\({}^{\circ}\) and HH polarization. The image shows palaeoriverbeds (pr), palaeochannels (pc), ancient land divisions (ald) and ancient roads. Red boxes denote the three investigated areas in relation to an ancient road and the palaeochannels A and B (indicated as pc_A and pc_B, respectively; see Figures 15, 17 and 19). Upper left : location of Metapontum in Southern Italy.