Multi-return LiDAR data North Carolina

http://www.grassbook.org/ncexternal/

### Steps to produce LAS:
# use GRASS GIS 7 for conversion
v.in.ogr lidar_raleigh_nc_spm.shp output=lidar_raleigh
v.out.ascii -c input=lidar_raleigh@lidar output=lidar_raleigh.csv columns=Class,Layer,Return format=point separator=, dp=3

# create LAS
txt2las -parse xyzscur --verbose lidar_raleigh.csv lidar_raleigh_nc_spm_height_feet.las


### Metadata
lasinfo lidar_raleigh_nc_spm_height_feet.las 
---------------------------------------------------------
  Header Summary
---------------------------------------------------------

  Version:                     1.2
  Source ID:                   0
  Reserved:                    0
  Project ID/GUID:             '00000000-0000-0000-0000-000000000000'
  System ID:                   'libLAS'
  Generating Software:         'libLAS 1.7.0'
  File Creation Day/Year:      0/0
  Header Byte Size             227
  Data Offset:                 227
  Header Padding:              0
  Number Var. Length Records:  None
  Point Data Format:           0
  Number of Point Records:     2269213
  Compressed:                  False
  Number of Points by Return:  1849787 365924 51283 2181 38 
  Scale Factor X Y Z:          0.01000000000000 0.01000000000000 0.01000000000000
  Offset X Y Z:                0.00 0.00 0.00
  Min X Y Z:                   633370.82 215000.01 88.50
  Max X Y Z:                   645000.00 228500.00 558.87
  Spatial Reference:           None

---------------------------------------------------------
  Schema Summary
---------------------------------------------------------
  Point Format ID:             0
  Number of dimensions:        12
  Custom schema?:              false
  Size in bytes:               20

  Dimensions
---------------------------------------------------------
  'X'                            --  size: 32 offset: 0
  'Y'                            --  size: 32 offset: 4
  'Z'                            --  size: 32 offset: 8
  'Intensity'                    --  size: 16 offset: 12
  'Return Number'                --  size: 3 offset: 14
  'Number of Returns'            --  size: 3 offset: 14
  'Scan Direction'               --  size: 1 offset: 14
  'Flightline Edge'              --  size: 1 offset: 14
  'Classification'               --  size: 8 offset: 15
  'Scan Angle Rank'              --  size: 8 offset: 16
  'User Data'                    --  size: 8 offset: 17
  'Point Source ID'              --  size: 16 offset: 18
  
---------------------------------------------------------
  Point Inspection Summary
---------------------------------------------------------
  Header Point Count: 2269213
  Actual Point Count: 2269213

  Minimum and Maximum Attributes (min,max)
---------------------------------------------------------
  Min X, Y, Z: 		633370.82, 215000.01, 88.50
  Max X, Y, Z: 		645000.00, 228500.00, 558.87
  Bounding Box:		633370.82, 215000.01, 645000.00, 228500.00
  Time:			0.000000, 0.000000
  Return Number:	1, 5
  Return Count:		0, 0
  Flightline Edge:	0, 0
  Intensity:		0, 0
  Scan Direction Flag:	0, 0
  Scan Angle Rank:	0, 0
  Classification:	0, 0
  Point Source Id:	0, 0
  User Data:		0, 3
  Minimum Color (RGB):	0 0 0 
  Maximum Color (RGB):	0 0 0 

  Number of Points by Return
---------------------------------------------------------
	(1) 1849787	(2) 365924	(3) 51283	(4) 2181	(5) 38

  Number of Returns by Pulse
---------------------------------------------------------
	(0) 2269213

  Point Classifications
---------------------------------------------------------
	2269213 Created, never classified (0) 
  -------------------------------------------------------
  	0 withheld
  	0 keypoint
  	0 synthetic
  -------------------------------------------------------