TOPOGRAPHIC SOLAR-RADIATION MODELS FOR GIS

Incident solar radiation at the Earth's surface is the result of a com plex interaction of energy between the atmosphere and the surface. Rec ently much progress has been made towards the creation of accurate, ph ysically-based solar radiation formulations that can model this intera ction over topographic and other surfaces (such as plant canopies) for a large range of spatial and temporal scales. In this paper we summar ize our current work on solar radiation models and their implementatio n within both GIS and image processing systems. An overview of the eff ects of topography and plant canopies on solar radiation is presented along with a discussion of various options for obtaining the data nece ssary to drive specific solar radiation models. Examples are given fro m our own work using two models, ATM (Atmospheric and Topographic Mode l), a model based within an image processing framework, and SOLARFLUX, a GIS-based model. We consider issues of design, including GIS implem entation and interface, computational problems, and error propagation.