Studying of solar radiation is essential to estimate its amount at ground level. In practice, there are two sources of solar data; the first consists of the measured ground data available in meteorological networks and radiometric solar stations. And, the other consists of extracting solar data from digital satellite images. However, only a few stations measured irregularly the amount solar radiation. Hence, in this paper, we will present a description and classification of some solar radiation estimation models based on ground measurements. Moreover, satellite image processing models are also discussed, an improvement of these models using fuzzy logic is also viewed. The validity of these models will be judged by comparing the obtained results by actually measured values of the available ground stations.