View full-text article in PMC Sensors (Basel). 2021 May 26;21(11):3703. doi: 10.3390/s21113703 Search in PMC Search in PubMed View in NLM Catalog Add to search Copyright and License information © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). PMC Copyright notice Algorithm 1. GPCA outliers removed Input:S(n×3 points) Output: Sf(nf×3 points),Sw(nw×3 points) 1: S=(xn,yn,zn) 2: μ=1n∑i=1nxi,1n∑i=1nyi,1n∑i=1nzi 3: for each point pi=(xi,yi,zi)∈S do 4: pi=pi−μ 5: end for 6: C=S 7: Γ=1nCTC 8: UΣVT=Γ 9: V=t1,t2,t3 10: ΔT=(t1,t2) 11: Sq=SΔT 12: bx=xmax−xmin/l 13: by=ymax−ymin/l 14: for each pointvi=xi,yi∈Sq do 15: hxi=round((xi−xmin)/bx) 16: hyi=round((yi−ymin)/by) 17: hi=(hxi,hyi) 18: end for 19: for each grid (i,j) do 20: Count the number kij of points in each cell 21: if kij<kσ then 22: Noise f ← Points in grid (i,j) 23: else 24: Wall points w ← Points in grid (i,j) 25: end if 26: end for 27: Get Sf and Sw