Scale LiDAR Intensities

kgroverkgrover Global Mapper UserPosts: 23Trusted User
edited May 2014 in Technical Support
I have a few aerial datasets, and a few of them have intensities between 0 and 255 and look good, but others indicate intensities between 0 and 5100 for some reason. When viewed in GM, the ones from 0 to 5100 are really dark. I can adjust the brightness of the display of the intensities to look better, but is there a way to actually bulk scale the intensities to try to get it closer to the 0 and 255?? I could export to txt and scale in excel, but these are giant files and would take a long time.

Not sure if there is another way??

Kevin

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2014
    Kevin,

    Do you have a sample point cloud with the large intensity range that you could provide? Currently for point clouds with intensities outside 0-255 GM calculations the average and standard deviation of the intensity values that are present, then scales a 0-255 grayscale from the average - 2 standard deviations to the average + 2 standard deviations, so you should get a pretty good color variation across the available values. This just wouldn't work well if all of the values were clustered around the minimum and maximum or something like that rather than spread out.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • kgroverkgrover Global Mapper User Posts: 23Trusted User
    edited May 2014
    Hi Mike,

    I have attached a zip file of a las in the link. From what I can see the intensities seem to be small as in the other files, but they do appear to be clustered to the minimum ranges of 0 and 5100. I got the 0 and 5100 info from the lasinfo utility online, but don't know if that is in the header of the LAS, or just what it is reading.

    https://www.dropbox.com/s/bnm22pkxihapynd/083H11F01.zip

    Kevin
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2014
    Kevin,

    Thanks for the file. I took a look and found that indeed almost all of the values were below 255 except for a handful scaling all the way up to 5100. I've improved the render logic for this case and now it looks much better automatically. I have placed new builds with the latest changes at the links below:

    32-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper15.zip
    64-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper15_64bit.zip

    Simply download the .zip file for the build that you are using and extract over your existing installation files. The likely locations to extract to are as follows:

    32-bit: C:\Program Files (x86)\GlobalMapper15
    64-bit: C:\Program Files\GlobalMapper15_64bit

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • kgroverkgrover Global Mapper User Posts: 23Trusted User
    edited May 2014
    Thanks Mike, it works great!!

    I did also find another way to edit the files themselves, since it was actually a problem with the las files on their own. The las2las utility from rapidlasso is an open source tool, and was able fix them with it. I set it to read the las files, keep only the intensity values under 255, then scale the intensity values by about 3 times (not sure why there were so low, but it matched closer with the other data I had), then resaved the las files.

    Regardless, the solution in GM will help for any other files I have in the future too!!

    Thanks.

    Kevin
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