Automated Reconstruction of Parametric BIM for Bridge Based on Terrestrial Laser Scanning Data

Algorithm 1

Point cloud projection filter segmentation.

Input: initial point cloud Datan × 3; neighborhood value m; threshold T;
Output: processed point cloud PCn-i × 3
(1)	Datax = Datan × 3 (:, 1);
(2)	Datay = Datan × 3 (:, 2);
(3)	PC = [Datax, Datay];//Project the point cloud of the precast box girder to the y direction.
(4)	Neighbor search (PC);//Find m neighborhood points of each point in PC.
(5)	Dn × m-1;//Construct the distance matrix.
(6)	n × 1 = Dn × m-1 × [1/m]m-1 × 1;//Calculate the average distance between each point and its domain point.
(7)	μ, σ;//Calculate the mean and standard deviation of the distribution.
(8)	for i = 0: n do
(9)	if i>μ + Tσ;//Determine the points with average distances that are greater than the threshold.
(10)	then
(11)	n-i × 1 =  n × 1\i;//Delete eligible distances.
(12)	PCn-i × 3;//Determine the coordinates after the segmentation.
(13)	end if
(14)	end for
(15)	return PCn-i × 3