Estimating Exposure Roughness Based on Google Earth

Abstract

Exposure roughness is significant in the evaluation of design wind loads. The roughness length (z0) is a key parameter to determine the exposure coefficient. In current wind load provisions, z0 is determined generally according to the exposure categories. However, subjective interpretation of upstream roughness by designers may lead to disagreements of exposure type. To address this issue, a more accurate method of determining the value of z0 is proposed in this paper. This approach uses morphometric methods in combination with the application of Google Earth Pro or equivalent. A three-dimensional modeling methodology is proposed which is based on the two-dimensional images captured in Google Earth Pro. The city center of London, UK and Tampa International Airport, US are chosen as case studies to verify the accuracy of the proposed method by comparison with available measured data. The comparison shows that this method works well for the estimation of z0 of upstream exposure.