Cloth Simulation Filter

Author: O.Conrad (c) 2026
Menu: Shapes | Point Clouds | Classification

Description

Airborne LiDAR ground/off-ground filtering method based on Cloth Simulation (CSF) as proposed by Zhang et al. (2016) and implemented by Jianbo Qi. In 3D computer graphics cloth modeling is used for cloth simulation by fitting the shape of cloth as represented by a finite number of particles according to physical laws. The CSF is mainly controlled by four user-defined parameters (Zhang et al 2026):

cloth grid resolution, which represents the horizontal distance between two neighboring particles
time step, which controls the displacement of particles from gravity during each iteration
rigidness, which controls the rigidness of the cloth
a slope smoothing option, which indicates whether the handling of steep slopes is required during post-processing

In addition, two threshold parameters are used to aid the identification of ground points. The first is a distance threshold, that governs the final classification of the LiDAR points as either ground or off-ground based on the distances to the cloth grid. The second threshold parameter is the height difference, which is used during post-processing to determine whether a movable particle should be moved to the ground or not.

References

CSF Github Repository
Zhang, W. , Qi, J., Wan, P., Wang, H., Xie, D., Wang, X. & Yan, G. (2016): An Easy-to-Use Airborne LiDAR Data Filtering Method Based on Cloth Simulation. Remote Sens., vol. 8, no. 6, p. 501. doi:10.3390/rs8060501

Parameters

	Name	Type	Identifier	Description	Constraints
Input	Points	point cloud, input	`POINTS`	-	-
Output	Ground Points	point cloud, output	`GROUND`	-	-
Output	Off-Ground Points	point cloud, output	`OFF_GROUND`	-	-
Options	Field	table field	`FIELD`	-	-
	Output	choice	`OUTPUT`	-	Available Choices: [0] attribute field [1] delete off-ground points [2] ground points [3] off-ground points [4] ground and off-ground points Default: 0
	Classification	choice	`ASPRS_LAS`	-	Available Choices: [0] 0=off-ground, 1=ground [1] ASPRS LAS Standard Default: 1
	Cloth Grid Resolution	floating point number	`cloth_resolution`	-	Minimum: 0.000000 Default: 0.500000
	Time Step	floating point number	`time_step`	-	Minimum: 0.000000 Default: 0.650000
	Rigidness	integer number	`rigidness`	-	Minimum: 1 Default: 3
	Slope Smoothing	boolean	`bSlopeSmooth`	-	Default: 1
	Distance Threshold	floating point number	`class_threshold`	-	Minimum: 0.000000 Default: 0.500000
	Height Difference	floating point number	`height_threshold`	-	Minimum: 0.000000 Default: 0.300000
	Maximum Iterations	integer number	`iterations`	-	Minimum: 1 Default: 500

Command Line


Usage: saga_cmd pointcloud_tools 17 [-POINTS ] [-GROUND ] [-OFF_GROUND ] [-FIELD ] [-OUTPUT ] [-ASPRS_LAS ] [-cloth_resolution ] [-time_step ] [-rigidness ] [-bSlopeSmooth ] [-class_threshold ] [-height_threshold ] [-iterations ]
  -POINTS:                Points
	point cloud, input
  -GROUND:                Ground Points
	point cloud, output
  -OFF_GROUND:            Off-Ground Points
	point cloud, output
  -FIELD:                 Field
	table field
  -OUTPUT:
                               Output
                               	choice
                               	Available Choices:
                               	[0] attribute field
                               	[1] delete off-ground points
                               	[2] ground points
                               	[3] off-ground points
                               	[4] ground and off-ground points
                               	Default: 0
  -ASPRS_LAS:
                               Classification
                               	choice
                               	Available Choices:
                               	[0] 0=off-ground, 1=ground
                               	[1] ASPRS LAS Standard
                               	Default: 1
  -cloth_resolution:   Cloth Grid Resolution
	floating point number
	Minimum: 0.000000
	Default: 0.500000
  -time_step:          Time Step
	floating point number
	Minimum: 0.000000
	Default: 0.650000
  -rigidness:             Rigidness
	integer number
	Minimum: 1
	Default: 3
  -bSlopeSmooth:          Slope Smoothing
	boolean
	Default: 1
  -class_threshold:    Distance Threshold
	floating point number
	Minimum: 0.000000
	Default: 0.500000
  -height_threshold:   Height Difference
	floating point number
	Minimum: 0.000000
	Default: 0.300000
  -iterations:            Maximum Iterations
	integer number
	Minimum: 1
	Default: 500