Estimating radiant flux of nighttime light images from NASA’s Black Marble product

Recently, radiant flux has been proved as a more accurate measure of nighttime light (NTL) compared to radiance. To estimate radiant flux of NTL from nighttime light images accurately, we propose a practical methodology that considers the anisotropy of NTL using the viewing zenith angle (VZA)-radiance quadratic model and the VZA-intensity quadratic model. Our methodology is derived from rigorous physical derivations. To verify the validity and superiority of our proposed methodology, we generated radiant flux products across eight U.S. states using NASA’s Black Marble product. And comparative analysis based on radiant flux calculated using different methods demonstrates that radiant flux calculated using our method provides a more appropriate physical metric for assessing NTL intensity than that derived from previous isotropic models. We conclude that radiant flux considering the anisotropy of NTL is more suitable for quantifying NTL energy and ecological impacts.