Geomatics Approaches for Detecting Floating Macroplastic Litter: The Res4Seal Project

Plastic pollution along coastlines is one of today’s most pressing environmental issues. The resilience of plastic, coupled with its ubiquitous use, allows it to persist in marine environments for years, posing a threat not only to marine life but also to human health through the seafood consumption. While traditional methods like in-situ surveys can help monitor this pollution, they are time-consuming, expensive, and limited in scope. Fortunately, remote sensing technology offers a more efficient, large-scale solution for detecting plastics in our oceans. However, this approach still faces challenges such as atmospheric interference and limitations in resolution. To tackle this issue, the ReS4Seal project was developed, using advanced geomatic techniques to detect plastic debris both in the water and along the shoreline. For plastics floating in the sea, a three-tier classification model was created, leveraging Sentinel-2 satellite images combined with the Floating Debris Index, the Normalized Difference Vegetation Index, and the Otsu filter to automatically identify macroplastics. Meanwhile, high-resolution photogrammetric images from Remotely Piloted Aircraft Systems were used to detect shoreline plastics, producing detailed orthophotos that allowed for precise mapping and classification of plastic debris. The results show that these methods are not only effective in locating and tracking macroplastic pollution but also offer a standardized approach, using a 1x1 meter grid, which facilitates consistent data collection for future monitoring efforts. Additionally, spectral analysis of the high-resolution RGB orthophotos confirmed their potential for distinguishing different types of plastic waste. Overall, these innovative techniques provide a promising path forward in our fight to manage plastic pollution and protect our coastal ecosystems.