Simple LiDAR ground points classification and segmentation using PDAL

PDAL (Point Data Abstraction Library) comes with a couple of options to segment point clouds by classifying LiDAR ground points (an example unclassified point cloud is shown below) - Simple Morphological Filter (SMRF) or Progressive Morphological Filter (PMF).

I have found the SMRF method to be fast and produce reasonable results while the PMF method seems to take a much longer time to do the job. The steps to run ground classification on a LAS file are describe below.

1. In Windows, open up the OSGeo4W Shell.
   
   The OSGeo4W Shell is displayed.
2. In the OSGeo4W prompt, type in and run the command:
   
   C:\> pdal translate -i unclassified.las -o ground.las smrf -v 4
   
   Notes:
   -i unclassified.las is the input file
   -o ground.las specifies the output file
   smrf is the option to apply the Simple Morphological Filter
   -v 4 is the processing messages verbosity level
   
   Processing messages appear.
   
3. Display the ground classified LAS file in a viewer.
   
   
   
   
4. To use the Progressive Morphological Filter to perform the ground classification, type in the following command:
   
   C:\> pdal translate -i unclassified.las -o ground.las pmf -v 4
   
   Notes:
   -i unclassified.las is the input file
   -o ground.las specifies the output file
   pmf is the option to apply the Progressive Morphological Filter
   -v 4 is the processing messages verbosity level