Hi everyone. I am an undergraduate student doing a research on vegetation classification of 3D LiDAR point clouds and I am new to CloudComapre. Sorry if I ask stupid questions...
I acquired my 3D LiDAR points by the GEOSLAM Zeb Zero RT handheld laser scanner (HLS), and I used CSF plugin in CC to remove vegetation. The result was very good. Then, however, I encounter a problem, that when I want to compare the M2C3 distance of the CSF-processed point cloud with my baseline model point cloud, they show difference in position (attachment 1). As a result, my M3C2 distance was in complete grey (out of measurable distance).
My baseline point cloud was constructed from a government surveyed shapefile and turned into raster format by ArcGIS, currently in "adf file format" when being used in CC. It is in 6-digit gird system and I know CC only handles Cartesian coordinate system, so CC asked me to do a global shifting at first. (attachment 2) I assume my HLS has correct GPS record and the coordinates are in places. So is that the global shifting causes the position difference of my 2 point cloud? FYR, I have also attached the default setting of HLS scanned point cloud. (attachment 3)
Questions:
1. Is global shifting from 6-digit gird coordinate affect the actual position with the HLS scanned point cloud in GPS?
2. Any method to fix their positions so it is able to compare them in M3C2?
Thank you very much!
Coordination difference between 2 Point Clouds
-
EllenorLizee
- Posts: 2
- Joined: Tue Apr 21, 2020 2:18 pm
Coordination difference between 2 Point Clouds
- Attachments
-
- Default setting of HLS scanned point cloud
- Screenshot 2020-04-22 at 2.16.21 PM.png (70.04 KiB) Viewed 9904 times
-
- Global shifting of baseline point cloud
- Screenshot 2020-04-22 at 2.13.32 PM.png (62.93 KiB) Viewed 9904 times
-
- Position difference of 2 point cloud models
- Screenshot 2020-04-22 at 2.29.06 PM.png (123.93 KiB) Viewed 9904 times
Re: Coordination difference between 2 Point Clouds
Are you only applying the shift on one cloud? Normally you would need to apply the same shift on both clouds (if they both had large coordinates).
Other option: are you sure your raster grid geographic coordinate system the same as the GPS? (generally WGS84)
Other option: are you sure your raster grid geographic coordinate system the same as the GPS? (generally WGS84)
Daniel, CloudCompare admin
-
EllenorLizee
- Posts: 2
- Joined: Tue Apr 21, 2020 2:18 pm
Re: Coordination difference between 2 Point Clouds
Thank you so much for your prompt reply, Daniel!
I didn't apply the same global shifting, but I guess I fixed the problem.
I should've georeferenced my Zeb Revo HLS point cloud first! Just like here: https://www.youtube.com/watch?v=_eG-oj22YrY
Thank you so much for your help though.
I didn't apply the same global shifting, but I guess I fixed the problem.
I should've georeferenced my Zeb Revo HLS point cloud first! Just like here: https://www.youtube.com/watch?v=_eG-oj22YrY
Thank you so much for your help though.