[M-AG33] Satellite Land Physical Processes Monitoring at Medium/High/Very High Resolution

[MAG33-03] A Novel Harmonization Method for PlanetScope Constellation Imagery Leveraging a Graph-based Greedy Optimization Strategy

*楊 偉¹、Chen Ruilin²、Chen Jin² (1.千葉大学、2.北京師範大学)

キーワード：PlanetScope Constellation、Harmonization、Radiometric Inconsistency、Graph Optimization

The PlanetScope CubeSat constellation provides unprecedented high spatiotemporal resolution for Earth observations but is limited by radiometric inconsistencies resulting from sensor degradation and spectral configuration differences. Existing harmonization methods often rely on internal or external references, limiting harmonization to four of the eight spectral bands or restricting applicability to localized spatiotemporal scales. To address these limitations, we propose Harmoni-Planet, a novel harmonization method that leverages graph-based greedy optimization to achieve holistic radiometric consistency across all PlanetScope bands without requiring reference data. The method consists of two components: (1) graph construction, which integrates unharmonized image strips into a graph with nodes representing image strips and edges connecting intersecting strips, and (2) graph optimization, which iteratively minimizes radiometric inconsistencies between each strip and its intersecting strips to optimize consistency. Validated across four geographically diverse regions (the Nile, Beijing, Indonesia, and Greenland), Harmoni-Planet achieves substantial mean absolute error (MAE) reductions of 45%, 48%, 39%, and 26%, respectively, compared with smaller improvements obtained with the official algorithm (14%, 18%, 3%, and 10%, respectively). In addition to facilitating enhanced spatial and temporal comparability of PlanetScope imagery, Harmoni-Planet supports seamless integration with standard third-party reflectance products such as Landsat and Sentinel-2. Furthermore, it enables real-time harmonization for newly acquired imagery to accommodate the rapidly expanding data volume of PlanetScope constellation. Harmoni-Planet provides a practical solution to address cross-sensor radiometric inconsistencies, substantially improving the quality and reliability of PlanetScope data for diverse Earth observation applications.