Studies on Modelling Direct Solar Radiation in a GIS Environment

Clear sky solar radiation varies in response to latitude,elevation, surface gradient (slope) and orientation (aspect), as well as position relative to neighbouring surfaces. This paper presents a model for estimating daily direct solar radiation. The model is based on technology and theory of GIS, using DEM to caculate slope, aspect and shading. Compared with measured radiation in the south of Ningxia Hui Autonomous Region, the results of the model is in a high degree of accuracy and can be used in the fields of forestry, ecology, biology and agriculture.