This study introduces the implementation of a spatial disaggregation process for irradiance maps in Corsica. Conventionally adopted hypotheses are for the first time tested and the errors they induce are evaluated step by step. Horizons derived from a Digital Elevation Model (DEM) as well as the binary hypothesis for beam irradiance were assessed. It was found that the global irradiance decomposition is a significant source of error, with a measured root mean square error over 30%. The process was tested at six locations, and the results confirm in most cases that the process for downscaling the satellite derived maps from a 10 km to a 90 m grid leads to better irradiation estimations compared to ground measurements. Finally we show that radiation estimates at mountainous sites are enhanced in the early and late hours of the day. Spatial disaggregation is therefore considered particularly well adapted for complex relief zones such as the island of Corsica. This previous work allows concluding on a mapping procedure that can be useful for a future political and economical energetic plan. (c) 2012 Elsevier Ltd. All rights reserved.