Procedure 1: theoretical basis

• For a fixed sun position, the irradiance map for an arbitrary radiance sun is a multiple of the normalized irradiance map (i.e. the irradiance map for a unit radiance sun).

• For a fixed arbitrary diffuse horizontal irradiance and circumsolar region position, the irradiance map for an arbitrary anisotropic sky (clear or intermediate) is almost equal to a multiple of the normalized irradiance map (i.e. the irradiance map for a unit diffuse horizontal irradiance sky and a fixed circumsolar region position).

• For a fixed arbitrary diffuse horizontal irradiance, the irradiance map for an arbitrary overcast sky is almost equal to a multiple of the normalized irradiance map.