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Atmospheric Correction Matters: How ACIX-III Improves Land Observations from Space

A recently published paper in Remote Sensing presents results from a new comparison of seven widely-used atmospheric processing schemes. Dr Feng Yin and Prof Philip Lewis, NCEO scientists at University College London, were co-authors of the paper and developed the SIAC model which was included in the comparison report.

Why is the study important?

When satellites capture images of Earth, the atmosphere can distort what they see. Dust, water vapour, and aerosols scatter light, making it harder to measure land surface properties accurately. Correcting these effects, called atmospheric correction is essential for reliable data used in climate studies, agriculture, and environmental monitoring.

What’s new in this study?

The Atmospheric Correction Inter-Comparison eXercise (ACIX-III Land) is the first large-scale assessment of seven leading atmospheric correction processors for two cutting-edge imaging spectroscopy missions: EnMAP (Germany) and PRISMA (Italy). Researchers tested these processors on 90 diverse land scenes worldwide, comparing how well they retrieve:

• Surface reflectance (how much light the land reflects)
• Aerosol optical depth (particles in the air)
• Water vapour content

Key Findings:

• Most processors achieved surface reflectance uncertainties between 0.02 and 0.04, which is considered very good for hyperspectral data.
• Differences emerged in handling complex conditions like high aerosol loads or variable terrain.
• The SIAC model, developed by NCEO researchers Dr. Feng Yin and Prof. Philip Lewis at UCL, performed best overall in both accuracy and uncertainty.
• Accurate atmospheric correction underpins high-quality surface reflectance for any subsequent analysis—making this work critical for all Earth observation applications

Why is SIAC significant?

Dr. Yin originally developed SIAC during his PhD, partly for the ESA TRUTHS mission, but its design makes it broadly useful for any spaceborne multispectral and hyperspectral optical data. This adaptability ensures that SIAC can support future missions and global monitoring efforts

Why does this matter for NCEO?

Accurate atmospheric correction ensures that Earth observation data truly reflects what’s happening on the ground. This is vital for tracking land use change, monitoring ecosystems, and supporting climate action. ACIX-III sets a benchmark for future missions and highlights NCEO’s leadership in delivering world-class solutions for Earth observation.