LAS file provided in a different coordinate system that I need.

[Mihai Prelipceanu]

Hello

I am new here and I have the following problem:

I downloaded a LAS tile file from Illinois Geospatial Data Clearinghouse.

I was told that data comes in metric system, NAD 83, UTM Zone 16N and NAVD88,

but I need it in US survey feet, NAD83, Illinois-East Zone, and NAVD88.

 

The LAS file has about half a million points and I would like to convert it in a TXT file

that can be used my coordinate system. I also can import LAS data in my photogrammetric

software, but the LAS data has to be converted first.

 

What LAS tool do I need? LAS2TXT doesn’t provide settings for the output file.

Do I need a Geographic Calculator for this task?

Thanks a lot for any advice.

Regards

Mihai

[Evon Silvia]

las2txt doesn't support reprojections. You'll just have to do what you want in two steps. Use las2las to change the units/projection, and then use las2txt to convert the resultant LAS files to TXT files. Something like...

• las2las -i utm.las -o spc.las -target_spc83 IL_E -target_survey_feet -target_elevation_survey_feet
  
• las2txt -i spc.las -o spc.txt -parse xyz
  

If you need more efficiency, use LAZ and/or look into Martin's piping workflow.

Evon

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[Martin Isenburg]

Hello,

indeed. As long as you do not change DATUM (and you don't as you stay within NAD83) you can use las2las.

http://rapidlasso.com/las2las

http://lastools.org/download/las2las_README.txt

Then you would go from EPSG code 26916 to EPSG code 3435

http://spatialreference.org/ref/epsg/nad83-utm-zone-16n/

http://georepository.com/crs_3435/NAD83-Illinois-East-ftUS.html

add the navd88 info and convert the vertical units from meters to US feet. Either of these two command lines should do the trick:

las2las -i in.laz ^

            -epsg 26916 ^

            -vertical_navd88 -elevation_meter ^

            -target_epsg 3435 ^

            -target_elevation_survey_feet ^

            -o out.laz

las2las -i in.laz ^

            -nad83 -utm 16n ^

            -vertical_navd88 -elevation_meter ^

            -target_epsg 3435 ^

            -target_elevation_survey_feet ^

            -o out.laz

but they don't because there is a small bug of not setting  US feet for the target coordinates so that you get coordinates scaled in meters despite the EPSG code stating otherwise. I already fixed this for the next release but I can send you the fixed executable already now (send me a private message).

You can then output text with las2txt or directly specify text output (use '-o out.txt' instead).

http://rapidlasso.com/las2txt

http://lastools.org/download/las2txt_README.txt

Regards,

Martin @rapidlasso