Rapid Estimation of Sky View Factor and Its Application to Human Environment

Abstract

It is common practice to parameterize urban canyon geometry as a sky view factor to be used to estimate surface radiation budgets. However, it is found that existing techniques of the computation of sky view factors are tedious, time consuming, erroneous and has often limited to just a few study cases. A fully automated digital approach to calculate sky view factors from fisheye photos is presented here. The validity of the new automated technique was tested by a series of inter comparison with other manual methods, which produces nearly identical results. The technique was applied in real conditions and it was found that increased sky obstruction significantly decreases the loss of long wave radiation in the nighttime and thus affects cooling rates.