# Improving the RST-OIL Algorithm for Oil Spill Detection under Severe Sun Glint Conditions
## 4 Discussion
Regardless, the results obtained are still satisfactory because it is worth mentioning that the main goal of the technique proposed is not to provide detailed oil mapping but to give an effective and timely alert in case of an accident. Figure 14: TCNNA shape files (violet) for (**a**) 25 April 2010 at 11:50 GMT (TerraSAR) data (overlapping on MODIS RGB of 25 April 2010 at 18:55 GMT) and (**b**) 29 April 2010 at 03:45 GMT (Envisat) data (overlapping on MODIS RGB of 29 April 2010 at 16:55). Figure 15: Comparison between the new proposed RST-OIL approach (green) and the TCNNA methodology (violet) for both test case images: (**a**) 25 April 2010 at 18:55, and (**b**) 29 April 2010 at 16:55. Through the analyzed MODIS time-series images (Figures 9-11), it was possible to estimate the accidental oil evolution in the temporal domain (Figure 16). Despite the possible oil slick underestimation discussed previously, the oil area profile reported in Figure 16 is in very good agreement with the results of another independent study [20], which coherently matches the phases that characterized the accident. The observed variability seems to be linked to a progressive oil accumulation. Once sunk, the DWH platform continued to spill oil into the sea, which accumulated more and more on the surface. Starting from 21 April 2010 (the day after the event), the competent authorities tried various actions to stop the oil spill [51]. In the first few days after the event, an attempt was made to act on the exhaust blocking valves. Then, an attempt was made to contain the spilled oil, and toward the end of May, the first operations to pump mud into the wells were attempted to try to cement it. However, all of these operations had no success. It is, therefore, necessary to wait for the month of June to witness the first successful interventions, which will be completed at the end of July with the entire containment of the spill. The results achieved in this work indicate a few limitations of the proposed approach. Cloud cover affects the achieved results with a two-fold contribution. On one hand, clouds may completely mask the sea surface, hampering any detection. On the other hand, a cloud mask that is not completely accurate may affect the accuracy of the produced outputs. Few areas could not be considered in the analysis because they were erroneously detected as being affected by the cloud. Further analyses have to be carried out on this topic to refine cloud detection schemes and further enhance the quality of the achieved results. Moreover, oil slick characterized by a negative contrast may be difficult to discriminate from the surrounding waters due to the very low range of variability of the investigated signal under such conditions, which is also very complicated for detection from a statistical point of view. A possible solution to face such an issue could be to consider, as an unperturbed condition, the minimum historically recorded value at the pixel level in place of the medium one. Proposed work can be open to other future developments, which may even involve exploiting the advanced capabilities offered by new generation sensors, such as the Ocean and Land Color Instrument (OLCI) onboard the Copernicus Sentinel-3 mission (in orbit since April 2018). The instrument, which has a similar spatial resolution to MODIS (i.e., 300 m), has a higher spectral capability and was specifically developed for sea surface observation. Furthermore, OLCI data may be integrated with those acquired by the Multi Spectral Imager (MSI) onboard the Copernicus Sentinel-2. This sensor, which is fully operational on both Sentinel-2A (in orbit since June 2015) and Sentinel-2B (in orbit since March 2017) ensures the availability of data with a spatial resolution of up to 10 m in the VNIR bands, which allows an increase in sensitivity, even for small spills.