Clearing Cloudy Satellite Signals For Better Earth Imaging

Scientists have devised a novel cloud screening method for satellite imaging, enabling accurate and high-resolution Earth monitoring.

AsianScientist (Jan. 14, 2022) – While cloudy skies can obscure satellite imaging data, a Hong Kong-US team has shown that every cloud has a silver lining, developing observational methods to improve the accuracy and spatial resolution of Earth monitoring efforts. The study was published in Remote Sensing of Environment.

Whether natural or human-accelerated, the planet is constantly undergoing environmental changes, from loss of forest cover to rivers encroaching on land. Satellite sensors can sweep across the entire globe every few days, sending images of Earth’s surface to help researchers to assess the ongoing impacts of human activities.

However, satellite sensing can typically only provide a bird’s eye view, with data signals muddled by clouds, shadows and varying sunlight angles. With observational methods that can only discern large-scale changes, such as the disappearance of acres of forest, researchers may prove too late in detecting and mitigating rapid environmental destruction.

To better track fine-grained changes from space, Dr. Wang Jing from the University of Hong Kong and colleagues have developed novel approaches to enhance the imaging data from nearly 200 sensors called CubeSats, leading to more accurate interpretations of the satellite signals.

This satellite constellation offers daily global coverage at three-meter resolution, meaning objects three meters apart are recognized as separate pixels to produce highly detailed images of the planet’s surface.

Further fine-tuning the image quality, the team’s automatic cloud and shadow screening method clears up hazy skies regardless of season and land type, from savannas to urban areas.

Besides high-accuracy cloud detection, efforts from the same lab have involved rigorous calibration to improve data consistency as well as overcome persisting issues with sunlight and reflection angles that interfere with satellite sensors. These processing techniques allow for more detailed monitoring, including distinguishing between leafy and leafless treetops.

By keeping a watchful eye over the Earth at such fine scale, the researchers envision that developments in CubeSats and other remote sensing technologies can propel ecological research, climate change impact assessments and environmental mitigation projects to better protect the future of the planet.

“Our research has made significant observational advances to make full use of these new-generation satellite data and ultimately facilitate the monitoring of Earth’s environmental changes, especially for rapid and fine-scale changes,” Wang concluded.

The article can be found at: Wang et al. (2021) Automatic cloud and cloud shadow detection in tropical areas for PlanetScope satellite images.


Source: The University of Hong Kong; Photo: Shutterstock.
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