Abstract
Configuration factor can be obtained either from an area of orthographic projection on the unit-sphere method or from a means of illuminance calculation. The illuminance values can be obtained from dimensions of a building or horizontal and vertical angle values from calculating point by the via-perspective method. Therefore the calculation method using illuminance values is better rather than measuring the area of distorted figure which looks like particular barrel for orthographic projection on the unit-sphere method. Especially a method using angle values method is useful for computing required value rapidly from values measured by a transit at actual spot.
