A simple analytical model which can predict accurately the sonic boom pressure signature on the ground in the vertical plane below a supersonic aircraft flying at constant horizontal speed in stratified atmosphere is presented. The proposed model employs geometrical acoustics to propagate the boom and combines a nonlinear treatment of its amplitude with a nonlinear calculation of its distortion, supplemented by the ”area rule” for shocks fitting; ray-tracing equations are derived to calculate the rays trajectory and the ray-tube area, considering the standard atmosphere. Although simple, this combined method allows a very efficient and accurate prediction of the boom propagation starting from a given pressure signal in the near-field and can be considered a useful tool for the aerodynamic design and multi-objective optimization of low-boom supersonic aircrafts via CFD methods. Comparisons with recent experimental data and previously published results obtained via well established sonic boom propagation codes are provided.