Close Shot Photogrammetry for Measuring Wind-Drifted Snow Distribution on Stepped Flat Roofs

A contactless inspection using a household digital camera (close shot photogrammetry) is introduced to improve measurement of wind-drifted snow distribution on the lower roof of a stepped flat roof model. Based on the image processing technique, a series of wind tunnel tests under different wind directions are investigated. Then 3-dimensional coordinates of the target points are calculated. Two typical directions are presented and discussed. The calculation results indicate that snow distribution on the lower roof appears to be concave when it is on the windward side. The maximum snow depth is located at the step, and the magnitude is about 2.78 order of the average snow depth. When the lower roof is on the leeward side, the distribution appears to be convex. The maximum depth located 1. OH away from the step, and the magnitude is about 1.2 order of average depth.