Sky-view factor approximation using GPS receivers

A technique is described which allows the real time measurement of sky-view factors by proxy. A simple and inexpensive global positioning system (GPS) receiver is used to acquire satellite visibility data, which is then used to develop indices related to the sky-view factor of a location. The number of visible satellites, dilution of precision and strength of satellite signal are used for analysis and demonstrate that up to 88% of the variation of the variation of the sky-view factor in urban environments can be explained by a simple index. Explanation is reduced in rural (R-2 = 72%) and suburban (R-2 = 52%) environments as a consequence of increased image complexity caused by variations in tree cover type and canopy height in addition to just crown closure. The complicity and expensive nature of existing sky-view factor calculation techniques should mean that utilization of the outlined methodology will improve the accessibility of sky-view data for future climate studies. Copyright (C) 2002 Royal Meteorological Society.