Satellite Imagery
This method of detection makes use of the existing satellite systems orbiting the earth in the thermosphere and stratosphere (38). Photographic and geographic information are collected simultaneously to facilitate the detection and tracking of plastic pollution in waterways.
Data Collection
Multi-Spectral Instruments (MSI) allow satellites to passively collect images of the earth's waterways as they travel along their orbital. This photographic data is linked with GPS coordinates that allow for accurate identification of plastic litter hot spots (9).
Image Processing
Using computer algorithms and Machine Learning (ML), the photos taken can be analyzed to identify and classify objects within (4). This is possible due to the unique optical properties of floating materials in comparison to the surrounding water. Plastics and natural debris have unique spectral reflectance levels in the near infrared (NIR) and shortwave infrared (SWIR) light ranges, unlike the ocean, which is a dark target with low reflectance (7). While water absorbs waves in these light ranges, floating materials like plastic reflect them. This allows satellites to detect debris from space (4).
