Impacts of DEM Geolocation Bias on Multiscale Validation of Land Surface Albedo Over Rugged Terrain

Quantitative evaluation of errors caused by Digital Elevation Model (DEM) geolocation bias is crucial for the multiscale validation of land surface albedo (LSA) over rugged terrain, as it provides a deeper understanding of topographic effects and helps minimizing validation uncertainties. This letter simulates the near-infrared band (NIR, 850 nm) fine scale albedo maps and coarse scale albedo by (large-scale remote sensing data and image simulation framework) LESS model, and shifts the DEMs along the different directions to aggregate to different coarse scales. The Mountain-Radiation-Transfer-based (MRT-based) albedo upscaling model was used to aggregate to the coarse scale. The results demonstrate that the errors distribution caused by DEM offsets is related to the terrain features. The primary factors influencing these errors are the average slope and coarse scale. Error increases with steeper slopes and decreases with larger coarse scales. Specifically, at 250 m, for terrains with a mean slope of approximately 25°, when the DEM is shifted by 4 pixels in both row and column directions, the errors can exceed 0.08, which is 4.5 times greater than those for gentle slopes (mean slope ≈ 5°). Minor DEM offsets are generally acceptable for gentle slopes and larger scales (>1 km), whereas precise DEM geolocation is essential for steeper slopes (mean slope > 15°), particularly at smaller coarse scales.