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  lassplit:

  splits the input file(s) into several output files based on
  the point source ID of the points. In praxis, the input file
  will often be an on-the-fly merge of many files (such as a
  folder of LAS tiles) into a single input with the '-merged'
  option. As input the user can provide one or multiple file
  names or a text file containing a list of file names.

  Instead of splitting LAS/LAZ/BIN/ASCII files based on the
  point source ID they can also be split into many numbered
  files that each contain the same number of points (except for
  the last one) with the '-split 100000000' option, which would
  split ech time after 100 million points were written.

  The header information from the first file (e.g. VLRs, scale
  factor offset, ...) is used for each written output file while
  these LAS header attributes are updated:

    * number_of_point_records
    * number_of_points_by_return[5]
    * max_x, min_x, max_y, min_y, max_z, and min_z

  In case the '-merged' option is used, it may become necessary
  to change the x_scale_factor, y_scale_factor, z_scale_factor
  and/or the x_offset, y_offset, z_offset, values. In order to
  have more control over this process the user can reset those
  in the command line with

     -rescale 0.01 0.01 0.001
     -reoffset 600000 4000000 0

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

  http://lastools.org/
  http://groups.google.com/group/lastools/
  https://lidarbb.cr.usgs.gov/index.php?showforum=29
  http://twitter.com/lastools/
  http://facebook.com/lastools/

  Martin @lastools

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example usage:

>> lassplit -i lidar.las -olaz

splits the file "lidar.las" based on the point source ID into
files named "lidar.XXXXX.laz" where XXXXX corresponds to the
point source ID.

>> lassplit -i *.las -olas

splits all files that match "*.las" based on the point source
ID into files named "*.XXXXX.las" where XXXXX corresponds to
the point source ID.

>> lassplit -i *.las -merged -o flightlines.laz

merges files that match "*.las" and splits the result based on
the point source ID into files named "flightlines.XXXXX.laz" where
XXXXX corresponds to the point source ID.

>> lassplit -i *.las -merged -o chopped.las -digits 2 -split 10000000

merges all *.las files into one and then splits the result into
several output files that contain ten million points each and that
are called chopped.00.las, chopped.01.las, chopped.02.las, ...

>> lassplit -i big.txt -iparse xyztp -o split.laz -split 500000000

split the ASCII file "big.txt" that could, for example, contain 25
billion points one and then split it into several compressed
output LAZ files that contain 500 million points each that are
called split.00000.laz, split.00001.laz, split.00002.laz, ...

for more info:

C:\lastools\bin>lassplit -h
Please license from 'martin.isenburg@gmail.com' to use LAStools commercially.
Filter points based on their coordinates.
  -clip_tile 631000 4834000 1000 (ll_x ll_y size)
  -clip_circle 630250.00 4834750.00 100 (x y radius)
  -clip_box 620000 4830000 100 621000 4831000 200 (min_x min_y min_z max_x max_y max_z)
  -clip 630000 4834000 631000 4836000 (min_x min_y max_x max_y)
  -clip_x_below 630000.50 (min_x)
  -clip_y_below 4834500.25 (min_y)
  -clip_x_above 630500.50 (max_x)
  -clip_y_above 4836000.75 (max_y)
  -clip_z 11.125 130.725 (min_z, max_z)
  -clip_z_below 11.125 (min_z)
  -clip_z_above 130.725 (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
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_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 1 2
  -drop_wavepacket 0
Filter points with simple thinning.
  -keep_every_nth 2
  -keep_random_fraction 0.1
  -thin_with_grid 1.0
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
  -clamp_z_min 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
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
  -change_return_number_from_to 2 1
  -change_number_of_returns_from_to 0 2
Modify the classification.
  -set_classification_to 2
  -change_classification_from_to 2 4
Modify the point source ID.
  -set_point_source_to 500
  -change_point_source_from_to 1023 1024
Transform gps_time.
  -translate_gps_time 40.50
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
  -i flight0??.laz flight1??.laz -single
  -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 0.1 0.1 0.1
  -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
  -olas -olaz -otxt -obin -oqfit (specify format)
  -stdout (pipe to stdout)
  -nil    (pipe to NULL)
LAStools (by martin.isenburg@gmail.com) version 120116 (licensed)
usage:
lassplit -i *.las
lassplit -i *.las -merged -o flightlines.las
lassplit -i *.las -split 100000000 -digits 2
lassplit -i *.laz -merged -split 10000000 -o split.laz

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