Through different previous communication, we presented the techniques of cloud cover analysis by infrared spectrometry in use in different sites since now roughly two years. • In a first step we will present the results of Monte Carlo simulations of cloud shape distortion induced by the method of measurement, and define optimal values for detectors like field of view (°), number of detectors… • In a second step various “grid” methods were tested in order to provide a realistic view of the sky dome compared to those from wide angle digital pictures. Preliminary results will be presented and discussed.