Bridging Gaps in Aquatic Remote Sensing Reflectance Validation: Pixel Boundary Effect and Its Induced Errors

Area of Science:

• Oceanography
• Remote Sensing
• Geophysics

Background:

• Ocean color remote sensing is vital for monitoring marine biogeochemical processes.
• Accuracy of remote sensing reflectance (Rrs) is crucial but limited by scale mismatch between point measurements and pixel observations.
• Pixel boundary effects (PBE) introduce poorly quantified uncertainty in Rrs products.

Purpose of the Study:

• To introduce and validate the pixel-level spatial mismatch index (PSMI) for assessing spatial representativeness errors caused by PBE.
• To quantify the impact of PBE on Rrs accuracy across different sensors and bands.
• To develop a framework for measuring spatial deviation peaks and defining PBE windows.

Main Methods:

• Developed the pixel-level spatial mismatch index (PSMI).
• Utilized AERONET-OC data with MODIS/Aqua and OLCI/Sentinel-3A observations.
• Proposed a Riemann Stieltjes integral-based index and a baseline method for PBE window definition.

Main Results:

• PSMI effectively identified systematic Rrs deviation peaks at pixel edges.
• Observed sensor- and band-dependent characteristics of these deviation peaks.
• PBE was confirmed as an independent error source interacting with atmospheric and geometric errors.

Conclusions:

• PBE significantly modulates overall uncertainty in Rrs products through multifactor interactions.
• Incorporating pixel-scale effects into validation protocols is essential.
• The PSMI framework offers a valuable tool for assessing and mitigating Rrs uncertainties.