This tool flags or removes noise points in LAS/LAZ/BIN/ASCII files. The tool looks for isolated points according to certain criteria that can be modified via ‘-step 3’ and ‘-isolated 3’ as needed. The default for step is 4 and for isolated is 5. It is possible to specify the xy and the z size of the 27 cells separately with ‘-step_xy 2’ and ‘-step_z 0.3’ which would create cells of size 2 by 2 by 0.3 units.
The tool tries to find points that have only few other points in their surrounding 3 by 3 by 3 grid of cells with the cell
the respective point falls into being in the center. The size of each of the 27 cells is set with the ‘-step 5’ parameter.
The maximal number of few other points in the 3 by 3 by 3 grid still designating a point as isolated is set with ‘-isolated 6’.
By default the noise points are given the classification code 7 (low or high noise). Using the ‘-remove_noise’ flag will
instead remove them from the output file. Alternatively with the ‘-classify_as 31’ switch a different classification code
can be selected. Another option is the ‘-flag_as_withheld’ switch which sets the withheld flag on the points identified
It is also important to tell the tool whether the horizontal and vertical units are meters (which is assumed by default)
or ‘-feet’ or ‘-elevation_feet’. Should the LAS file contain proper projection VLRs then there is no need to specify this
explicitly. Internally the step size in xy or in z direction will be multiplied with 3 if the coordinates are found or are
specified to be in feet. The size of the grid cells needs to be changed with ‘-step 0.0001’ or similar if the input is in
geographic longlat representation.
You can avoid having certain points being classified, marked withheld, or removed with the ‘-ignore_class 2’ option.
See README file for more information.