The National Renewable Energy Laboratory of United States (NREL) has done an amazing job developing the Solar Prospector, a tool to navigate through data derived from satellite imagery with a resolution of 10×10 km. This mapping tool is designed to help developers site large-scale solar plants by providing easy access to solar resource datasets and other data relevant to utility-scale solar power projects.
Unfortunately the information is only for United States.
Accurate computation of solar position plays a fundamental role in solar energy applications, especially for concentrating systems. The required accuracy varies over a wide range, depending on the application: flat systems tolerate errors of a few degrees without significant losses, while high-concentration systems can require an accuracy of the order of 0.01º. More specific applications, such as the calibration of pyranometers ( Reda and Andreas, 2004 ), require an even greater accuracy.