Patent US 8,326,536

A computer-implemented system and method for correlating satellite imagery for use in photovoltaic fleet output estimation is provided. Pixels in satellite imagery data of overhead sky clearness is correlated to a bounded area within a geographic region. Each pixel represents collective irradiance that is converted into point clearness indexes for the points within the bounded area relative to clear sky irradiance. The point clearness indexes in the point clearness indexes are averaged for the points within the bounded area into an area clearness index. A variance of the area clearness index is determined in proportion to a physical area covered by each pixel. For each point, a variance of the point clearness index is determined as a ratio of the area clearness index variance and the physical area relative to the point clearness index, regional cloud speed, and a time interval relating to a time resolution of collective irradiance observation.