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.