A Method for Intelligent Extraction of Pseudoinvariant Calibration Sites Using Earth–Atmosphere Characteristic Coupling Analysis

Pseudoinvariant calibration site (PICS) calibration is an important method for ensuring the on-orbit radiometric accuracy of Earth observation satellites. The proper selection of calibration sites is essential for ensuring the quality of quantitative remote sensing data and consistency across various sensors. This study presents a PICS selection method based on object analysis and a comprehensive evaluation of multidimensional characteristics, identifying qualified sites in the Golmud region of the Qaidam Basin. In this study, Landsat 8 Operational Land Imager (OLI) remote sensing data and related auxiliary data from 2014-2023 are used to comprehensively evaluate the calibration site from multiple dimensions, including spatiotemporal spectral consistency, site flatness, climatic characteristics and trend stability. The results are as follows: (1) The proposed method selects sites with excellent attributes, with no significant correlation observed between spectral band consistency and spatiotemporal stability, indicating these should be treated as independent indicators. (2) Segmented objects based on the spatial neighbourhood intensity constraint (SLIC) serve as units for site selection, which is suitable for PICS selection at various scales and effectively prevents spatial fragmentation issues linked to pixel-scale selection based on coefficient of variation (CV). Compared with the sliding window method, the selected sites are better in terms of spatiotemporal stability, with the mean spatiotemporal CV decreasing from 1.699% to 1.594%. (3) The PICSs meeting the characteristic requirements are mainly distributed in the central Qaidam Basin and the northwestern area of Guolemude town. The CVs of both GRM<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\_$</tex-math></inline-formula>1 and GRM<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\_$</tex-math></inline-formula>2 are less than 1.6%, with a dry climate, low cloud coverage and precipitation, and a uniform surface, making them suitable as supplementary sites for high-frequency calibration and correction.