Abstract: A method of predicting the level of radio field and/or the duration of radio propagation of a mobile telephone network for the coverage of a cell using the ray tracing technique and utilizing geographical databases, wherein the database directly utilized is a matrix base composed of pixels, each pixel carrying at least an information item specific to the type of ground cover and an information item specific to the height of the ground cover, a vectorization processing is applied to the matrix base to linearize the contours of obstacles encountered while rays are fictitiously traced, the rays according to the obstacles encountered being either reflected or diffracted and scattered, whilst the global attenuation and/or propagation duration is calculated, the vectorization processing of the contours of obstacles being applied to matrix bases to linearize the contours of obstacles encountered by forming straight lines whose positions and various angles are known accurately.