On cloud bottom boundary determination by digital stereo photography from the Earth’s surface

Abstract

In this paper, we studied the method for measuring the cloud bottom boundary altitude using the stereo pair of cloud images obtained using two digital photo cameras. We suggested a method for determining the camera orientation parameters using the nighttime images of star sky. The range to the cloud is calculated using the shift of the image of a cloud fragment as a whole. A given fragment on the photographs is identified using the methods of morphological image analysis. When the stereo base is 60 m and images are taken with a resolution of 1200 pixels within a field of view of 60°, the uncertainty does not exceed 10% when cloud altitude is less than 4 km. Optimizing the parameters of photography and increasing the stereo base may substantially improve the accuracy of the cloud base altitude estimation. Examples are presented of cloud bottom boundary determination using a prototype of the experimental setup as compared to data of a laser range finder.