  Vision based haze density estimation is of practical implications for the
purpose of precaution alarm and emergency reactions toward disastrous hazy
weathers. In this paper, we introduce a haze density estimation framework based
on modeling of scattering coefficients of iso-depth regions. A haze density
metric of Normalized Scattering Coefficient (NSC) is proposed to measure
current haze density level with reference to two reference scales. Iso-depth
regions are determined via superpixel segmentation. Efficient searching and
matching of iso-depth units could be carried out for measurements via
unstationary cameras. A robust dark SP selection method is used to produce
reliable predictions for most out-door scenarios.
