Solar Radiation Resource assessment is a broad term that refers to the various aspects of solar radiation relevant to solar energy and related applications. The terms resource characterization, resource measurement, resource information, and resource evaluation all fall under the comprehensive definition of solar radiation resource assessment. Solar resource information is a significant input for a wide range of applications: collector and device testing, building simulations (with either architectural or HVAC emphasis), solar system simulation for feasibility, design, siting or operational purposes. For each application however, resource assessment may mean something quite different. For some applications, the information and tools available today may be more than adequate but for others it may fall far short. It is useful to classify solar resource information in terms of a physical quantity or parameter with specific temporal and spatial characteristics. Examples of physical quantities are global irradiance, direct illuminance, or zenith luminance. The temporal characteristics include time step (e.g., one-minute, hourly, daily, etc.) and time specificity (e.g., time specific, typical, average, stochastic, forecasted, real time, etc.). Spatial characteristics refer to geographical determination of the resource information. This information may be point specific (e.g., based on a single station) or extended (e.g., a gridded map). The main concern with point specific data is the information's validity as distance increases. The concern for extended resource information is its spatial resolution.