Creating Intensity data

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abdullah.kianejad

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Apr 18, 2015, 3:12:06 PM4/18/15

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Hello Dear Mr Martin Isenburg

I am kianejad. I have a LIDAR data with txt format.
I want to generate Intensity data from this LIDAR data. But, I don't know the best formula for this purpose. My data have some columns such as: Easting [m] Northing [m] Elevation [m] Pulse width [0.1 ns] Return number Reflectance [dB] Amplitude [0..1]
Please, help me for creating Intensity data.
Kind Regards
Kianejad

Martin Isenburg

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Apr 18, 2015, 4:28:25 PM4/18/15

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Hello Kianejad,

sounds like you have a file like that:

East [m] North [m] Elev [m] PW [0.1 ns] ret_count ret_num Refl [dB] Ampl [0..1]

1441.705 9921.431 350.757 4.2 2 2 12.48 0.6252

1441.717 9921.875 350.760 4.3 1 1 13.78 0.2188

1441.729 9922.332 350.751 4.3 1 1 13.22 0.1967

1441.736 9922.786 350.651 4.4 1 1 13.16 0.9005

1441.749 9923.249 350.660 4.4 1 1 13.98 0.2937

1441.760 9923.659 350.668 4.4 1 1 12.79 0.7432

1441.771 9924.098 350.653 4.2 1 1 10.99 0.1534

The intensity in LAS does not really have a well-defined "physical" meaning. I think in your case you would map the amplitude to the intensity by scaling the [0.0 1.0] range to fit either [0 65535] or [0 255] or whatever may make sense for you in between. In the PTS (or PTX?) format the range is often more like [0 4095].

I you also want to store the PulseWidth and the Relectance into the LAS / LAZ files (in form of extra bytes) then see this example description here:

http://groups.google.com/d/topic/lastools/DWQ2GXKE8f8/discussion

Attached are the sample files used / produced below.

txt2las -i kianejad.txt ^

-skip 1 ^

-parse xyzsrnsi ^

-scale_intensity 255.0 ^

-odix _int8bit -olas

WARNING: written 7 points but expected 0 points

txt2las -i kianejad.txt ^

-skip 1 ^

-parse xyzsrnsi ^

-scale_intensity 65535.0 ^

-odix _int16bit -olaz

WARNING: written 7 points but expected 0 points

lasinfo kianejad_int8bit.las

lasinfo for kianejad_int8bit.las

reporting all LAS header entries:

file signature: 'LASF'

file source ID: 0

global_encoding: 0

project ID GUID data 1-4: 00000000-0000-0000-0000-000000000000

version major.minor: 1.2

system identifier: 'LAStools (c) by rapidlasso GmbH'

generating software: 'txt2las (version 150406)'

file creation day/year: 108/2015

header size: 227

offset to point data: 227

number var. length records: 0

point data format: 0

point data record length: 20

number of point records: 7

number of points by return: 6 1 0 0 0

scale factor x y z: 0.01 0.01 0.01

offset x y z: 0 0 0

min x y z: 1441.71 9921.43 350.65

max x y z: 1441.77 9924.10 350.76

reporting minimum and maximum for all LAS point record entries ...

X 144171 144177

Y 992143 992410

Z 35065 35076

intensity 39 230

return_number 1 2

number_of_returns 1 2

edge_of_flight_line 0 0

scan_direction_flag 0 0

classification 0 0

scan_angle_rank 0 0

user_data 0 0

point_source_ID 0 0

overview over number of returns of given pulse: 6 1 0 0 0 0 0

histogram of classification of points:

7 never classified (0)

D:\LAStools\bin>lasinfo kianejad_int16bit.laz

lasinfo for kianejad_int16bit.laz