Mitigating Topographic Effects in Optical Remote Sensing: From surface reflectance to high-level products

Accurate estimation of environmental variables from satellite observations in mountainous terrain remains challenging as complex topography systematically alters the sun–target–sensor geometry. These terrain-induced distortions, including slope–aspect effects, shadowing, and terrain obstruction, are largely ignored by most operational satellite products. Given that mountainous regions occupy approximately 24% of Earth’s land surface, these errors introduce globally substantial uncertainties. This review provides a comprehensive synthesis of topographic correction and topography-aware strategies based on a retrieval chain. We reviewed the progress in reducing topographic impacts in surface reflectance in three strategies: 1) empirical and semiempirical methods, 2) physically based radiative transfer correction methods, and 3) combined atmospheric–topographic correction schemes. Furthermore, we critically examine the propagation of topographic effects and specific mitigation strategies across three key downstream domains: 1) surface radiation budget components [e.g., albedo, shortwave/longwave radiation, and land surface temperature (LST)]; 2) biophysical variables [e.g., vegetation indices (VIs), leaf area index (LAI), fraction of absorbed photosynthetically active radiation (FAPAR), and gross primary production (GPP)]; and 3) geophysical variables [specifically, snow cover and evapotranspiration (ET)].