Performances of driver assistance systems depend on weather conditions: when the later deteriorate, for instance due to fog or rain, the performances deteriorate too. We hereby present a new approach of modelling raindrops on the windshield using the declivity principle applied in different plans. Our goal is to define a profile of raindrops by analyzing intensities behavior in different planes -- horizontal, vertical, left-diagonal, and right-diagonal -- based on the declivity principle's properties.