Forum

Author Topic: Scale factor x y z in .las different after using subsample method  (Read 3224 times)

Sky_hie

  • Jr. Member
  • **
  • Posts: 67
    • View Profile
Hi.

I have used cloud compare to decimate a .las point cloud. Before subsampling I have 0.001 in x y and z scale (in point cloud from PS) and after subsampling in CC I have different number on the scales. Please see attachment.

Why is this happening? What does this mean? The point cloud is georeferenced in UTM coordinates..

Anyone?

thanks, SH

StevenF

  • Newbie
  • *
  • Posts: 39
    • View Profile
Re: Scale factor x y z in .las different after using subsample method
« Reply #1 on: December 09, 2014, 01:25:59 AM »
I don't know why CloudCompare is rescaling the data, but it's also changing the point data format. Both of these changes are going to making your las files bulkier than necessary. Even 0.001 (1mm) is too high for aerial collections. Your data probably doesn't have that level of accuracy.

I'd recommend using lastools to rescale and change the point format of your data to make it more compact.  See this lastools posting on fixing crappy las files.
 https://groups.google.com/forum/#!searchin/lastools/crappy$20las/lastools/oK81EEr7W3Y/pYBvwTzKOugJ.

Sky_hie

  • Jr. Member
  • **
  • Posts: 67
    • View Profile
Re: Scale factor x y z in .las different after using subsample method
« Reply #2 on: December 11, 2014, 02:53:25 PM »
I don't know why CloudCompare is rescaling the data, but it's also changing the point data format. Both of these changes are going to making your las files bulkier than necessary. Even 0.001 (1mm) is too high for aerial collections. Your data probably doesn't have that level of accuracy.

I'd recommend using lastools to rescale and change the point format of your data to make it more compact.  See this lastools posting on fixing crappy las files.
 https://groups.google.com/forum/#!searchin/lastools/crappy$20las/lastools/oK81EEr7W3Y/pYBvwTzKOugJ.

Thank you for the reply.

The scale factor of x, y and z, went from 0.001 to 0.00000035632something. Does this mean that the las file can not be thrusted for applications such as volume measurements and areameaurements? Will the Las file still represent the real world measurements correctly even thoug the different scaling?

Anyone?