“…This content can be grouped into three geometrically significant clusters with respect to surface normal distributions as: the horizontal structures, vertical structures, and clutter which might be existent as dissolved in any direction, anisotropically-heterogeneously, throughout the whole point cloud. The common approach to leave out walls in this mixed data, is to start with extracting ceiling and floor within horizontal structures, and further eliminate clutter from the remaining cloud (Oesau et al, 2014), (Mura et al, 2013), (Adan and Huber, 2011), (Okorn et al, 2010). For this purpose, the inherent density predominance of ceiling and floor is exploited in a point density histogram along the vertical axis, and clutter is removed by estimating surface normal, and filtering points whose normal are not parallel in the vertical direction.…”