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  lasground_new:

  This is a tool for bare-earth extraction: it classifies LIDAR
  points into ground points (class = 2) and non-ground points
  (class = 1). This is a totally redesigned version of lasground
  that handles complicated terrain much better where there are
  steep mountains nearby urban areas with many buildings.

  You can use other classifications than the ASRPS standard with
  '-ground_class 10' or '-non_ground_class 25'. It is possible to
  leave intact the original classification of any points that are
  not classified as ground with '-non_ground_unchanged'.

  The default step size has been increased to 25 meters, which
  allows to remove most buildings in common cities (except very
  large warehouses or factories which require a larger step). 
  For smaller towns or terrains with a few buildings use the
  '-town' option that decreases the step size to 10 meters. For
  very large cities use '-metro' and the step size is increased
  to 50 meters You can also experiment with setting it directly
  using '-step 35'. Then there is the '-nature' option that uses
  a step size of 5 meters for terrains without buildings and the
  '-wilderness' option that uses 3 meters if you care for smaller
  features on the ground in high resolution LiDAR.

  It is 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/LAZ file contain
  projection information then there is no need to specify this
  explicitly. If the input coordinates are in an earth-centered
  or a longlat representation, the file needs converted to, for
  example, a UTM projection first. That said, some folks have
  successfully ground-classified longlat representations using
  a very small '-step 0.000005' or so.

  By default the tool only considers the last return. Earlier
  returns are considered non-ground. You can turn this off by
  requesting '-all_returns'. If you want to leave out certain
  classifications from the bare-earth calculation you can do
  so with '-ignore_class 7'.

  For very steep hills you can intensify the search for initial
  ground points with '-fine', '-extra_fine', '-ultra_fine', or
  '-hyper_fine' and similarly for very flat terrains you can
  simplify the search with '-coarse' or '-extra_coarse' but try
  the default setting first. 

  The experienced user can fine-tune the algorithm further by
  specifing the threshold in meters at which spikes get removed.
  Setting '-spike 0.5' will remove up-spikes above 50 centimeter
  and setting '-spike_down 2.5' will remove down-spikes below 2.5
  meters in the coarsest TIN. The maximal offset in meters up to
  which points above the current ground estimate get included can
  be set with '-offset 0.1'. You can also - if you want to try a
  lot of settings - play with '-bulge 1.5' that - by default - is
  set to a tenth of the step size and then clamped into the range
  from 1.0 to 2.0.

  Finally you can ask lasground_new to compute the height above the
  ground for each point (so you can use lasclassify next without
  needing to run lasheight first) with '-compute_height' or even
  ask to have the computed height replace the elevation value with
  option '-replace_z'. Then you directly get a height normalized
  LAS/LAZ file that can be used, for example, with the lascanopy or
  lasgrid tools or the pit-free canopy height model (CHM) algorithm.

  Should lasground miss-behave try turning off some optimizations
  using the '-no_clean' or the '-no_bulge' flags.

  If there are too few points to do reliable ground classification
  then the files are simply copied (and in case of '-replace_z' all
  elevations are zeroed). Alternatively these files can be skipped
  with the command-line option '-skip_files'.

  Please license from martin@rapidlasso.com to use lasground_new
  commercially. Please note that the unlicensed version will set
  intensity, gps_time, user data, and point source ID to zero,
  slightly change the LAS point order, and randomly add a tiny
  bit of white noise to the points coordinates.

  For updates check the website or join the LAStools mailing list.

  http://rapidlasso.com/
  http://lastools.org/
  http://groups.google.com/group/lastools/
  http://twitter.com/lastools/
  http://facebook.com/lastools/
  http://linkedin.com/groups?gid=4408378

  Martin @lastools

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example usage:

>> lasground -i terrain.laz -o classified_terrain.laz

classifies a terrain with the default settings.

>> lasground -i terrain.laz -o classified_terrain.laz -feet -elevation_feet

classifies a terrain where both horizontal and vertical units are
in feet instead of in meters (which is assumed by default unless
there is projection information in the LAS file saying otherwise).

>> lasground -i terrain.laz -o classified_terrain.laz -all_returns

classifies a terrain considering all points - not just the last
returns (as is the default behavior).

>> lasground -i tiles_raw\*.laz -odir tiles_ground -olaz -cores 16

classifies all LAZ files from the tiles_raw folder with the default
settings on multiple cores and stores the result as LAZ files in the
tiles_ground folder (that must exist).

>> lasground -i *.laz -town -odix _g -olaz -cores 8

the same as above but uses finer spacing to allowing only smaller
buildings and other man-made structures to be removed.

>> lasground -i *.laz -metro -odix _ground -olaz -cores 4

the same as above but uses a wider spacing to allow removing very
large buildings such as warehouses and factories.

for more info:

D:\LAStools\bin>lasground_new.exe -h
Filter points based on their coordinates.
  -keep_tile 631000 4834000 1000 (ll_x ll_y size)
  -keep_circle 630250.00 4834750.00 100 (x y radius)
  -keep_xy 630000 4834000 631000 4836000 (min_x min_y max_x max_y)
  -drop_xy 630000 4834000 631000 4836000 (min_x min_y max_x max_y)
  -keep_x 631500.50 631501.00 (min_x max_x)
  -drop_x 631500.50 631501.00 (min_x max_x)
  -drop_x_below 630000.50 (min_x)
  -drop_x_above 630500.50 (max_x)
  -keep_y 4834500.25 4834550.25 (min_y max_y)
  -drop_y 4834500.25 4834550.25 (min_y max_y)
  -drop_y_below 4834500.25 (min_y)
  -drop_y_above 4836000.75 (max_y)
  -keep_z 11.125 130.725 (min_z max_z)
  -drop_z 11.125 130.725 (min_z max_z)
  -drop_z_below 11.125 (min_z)
  -drop_z_above 130.725 (max_z)
  -keep_xyz 620000 4830000 100 621000 4831000 200 (min_x min_y min_z max_x max_y max_z)
  -drop_xyz 620000 4830000 100 621000 4831000 200 (min_x min_y min_z max_x max_y max_z)
Filter points based on their return number.
  -first_only -keep_first -drop_first
  -last_only -keep_last -drop_last
  -keep_middle -drop_middle
  -keep_return 1 2 3
  -drop_return 3 4
  -keep_single -drop_single
  -keep_double -drop_double
  -keep_triple -drop_triple
  -keep_quadruple -drop_quadruple
  -keep_quintuple -drop_quintuple
Filter points based on the scanline flags.
  -drop_scan_direction 0
  -scan_direction_change_only
  -edge_of_flight_line_only
Filter points based on their intensity.
  -keep_intensity 20 380
  -drop_intensity_below 20
  -drop_intensity_above 380
  -drop_intensity_between 4000 5000
Filter points based on their classification.
  -keep_class 1 3 7
  -drop_class 4 2
  -drop_synthetic -keep_synthetic
  -drop_keypoint -keep_keypoint
  -drop_withheld -keep_withheld
Filter points based on their user data.
  -keep_user_data 1
  -drop_user_data 255
  -keep_user_data_between 10 20
  -drop_user_data_below 1
  -drop_user_data_above 100
  -drop_user_data_between 10 40
Filter points based on their point source ID.
  -keep_point_source 3
  -keep_point_source_between 2 6
  -drop_point_source 27
  -drop_point_source_below 6
  -drop_point_source_above 15
  -drop_point_source_between 17 21
Filter points based on their scan angle.
  -keep_scan_angle -15 15
  -drop_abs_scan_angle_above 15
  -drop_scan_angle_below -15
  -drop_scan_angle_above 15
  -drop_scan_angle_between -25 -23
Filter points based on their gps time.
  -keep_gps_time 11.125 130.725
  -drop_gps_time_below 11.125
  -drop_gps_time_above 130.725
  -drop_gps_time_between 22.0 48.0
Filter points based on their wavepacket.
  -keep_wavepacket 0
  -drop_wavepacket 3
Filter points with simple thinning.
  -keep_every_nth 2
  -keep_random_fraction 0.1
  -thin_with_grid 1.0
  -thin_with_time 0.001
Transform coordinates.
  -translate_x -2.5
  -scale_z 0.3048
  -rotate_xy 15.0 620000 4100000 (angle + origin)
  -translate_xyz 0.5 0.5 0
  -translate_then_scale_y -0.5 1.001
  -switch_x_y -switch_x_z -switch_y_z
  -clamp_z_below 70.5
  -clamp_z 70.5 72.5
Transform raw xyz integers.
  -translate_raw_z 20
  -translate_raw_xyz 1 1 0
  -clamp_raw_z 500 800
Transform intensity.
  -scale_intensity 2.5
  -translate_intensity 50
  -translate_then_scale_intensity 0.5 3.1
  -clamp_intensity 0 255
  -clamp_intensity_above 255
Transform scan_angle.
  -scale_scan_angle 1.944445
  -translate_scan_angle -5
  -translate_then_scale_scan_angle -0.5 2.1
Change the return number or return count of points.
  -repair_zero_returns
  -set_return_number 1
  -change_return_number_from_to 2 1
  -set_number_of_returns 2
  -change_number_of_returns_from_to 0 2
Modify the classification.
  -set_classification 2
  -change_classification_from_to 2 4
  -classify_z_below_as -5.0 7
  -classify_z_above_as 70.0 7
  -classify_z_between_as 2.0 5.0 4
  -classify_intensity_above_as 200 9
  -classify_intensity_below_as 30 11
  -change_extended_classification_from_to 6 46
Change the flags.
  -set_withheld_flag 0
  -set_synthetic_flag 1
  -set_keypoint_flag 0
  -set_extended_overlap_flag 1
Modify the extended scanner channel.
  -set_extended_scanner_channel 2
Modify the user data.
  -set_user_data 0
  -change_user_data_from_to 23 26
Modify the point source ID.
  -set_point_source 500
  -change_point_source_from_to 1023 1024
  -quantize_Z_into_point_source 200
Transform gps_time.
  -translate_gps_time 40.50
  -adjusted_to_week
  -week_to_adjusted 1671
Transform RGB colors.
  -scale_rgb_down (by 256)
  -scale_rgb_up (by 256)
Supported LAS Inputs
  -i lidar.las
  -i lidar.laz
  -i lidar1.las lidar2.las lidar3.las -merged
  -i *.las - merged
  -i flight0??.laz flight1??.laz
  -i terrasolid.bin
  -i esri.shp
  -i nasa.qi
  -i lidar.txt -iparse xyzti -iskip 2 (on-the-fly from ASCII)
  -i lidar.txt -iparse xyzi -itranslate_intensity 1024
  -lof file_list.txt
  -stdin (pipe from stdin)
  -rescale 0.01 0.01 0.001
  -rescale_xy 0.01 0.01
  -rescale_z 0.01
  -reoffset 600000 4000000 0
Supported LAS Outputs
  -o lidar.las
  -o lidar.laz
  -o xyzta.txt -oparse xyzta (on-the-fly to ASCII)
  -o terrasolid.bin
  -o nasa.qi
  -odir C:\data\ground (specify output directory)
  -odix _classified (specify file name appendix)
  -ocut 2 (cut the last two characters from name)
  -olas -olaz -otxt -obin -oqfit (specify format)
  -stdout (pipe to stdout)
  -nil    (pipe to NULL)
LAStools (by martin@rapidlasso.com) version 150125 (commercial)
usage:
lasground_new -i in.laz -o out.laz
lasground_new -i *.laz -odix _g -olaz -cores 4
lasground_new -i in.las -o out.laz -metro
lasground_new -i in.laz -o out.laz -town -ignore_class 7
lasground_new -i in.laz -o out.laz -v -step 45 -spike 1.5 -down_spike 2.5 -bulge 2.5 -offset 0.1
lasground_new -i in.las -o out.laz -feet -elevation_feet
lasground_new -i in.laz -o out.laz -no_bulge
lasground_new -i *.laz -v -odir ground_classified -olaz -cores 8
lasground_new -h

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if you find bugs let me (martin.isenburg@rapidlasso.com) know.
