{'fraction_non_alphanumeric': 0.016357688113413305, 'fraction_numerical': 0.0, 'mean_word_length': 5.3310344827586205, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Influence of DEM and BRDF effects on the radiometric correction of satellite imagery

The calculation of ground reflectance imagery from satellite scenes acquired over mountainous terrain depends on a number of factors. Two factors are considered here: the spatial resolution of the Digital Elevation Model (DEM) and bidirectional reflectance (BRDF) effects. Due to the large range of local solar incidence angles in a rugged terrain a strong departure from the isotropic reflectance behavior is often apparent in the imagery. Simple empirical functions are offered to reduce the BRDF influence for the reflectance image product. DEM errors, an inadequate spatial resolution or a small sub-pixel misregistration between an image pixel and the DEM resolution cell lead to reflectance errors. The magnitude of this error is wavelength-dependent. Some typical configurations are investigated to assess the DEM influence.