Importing point cloud xyz

scrscr Global Mapper UserPosts: 42Trusted User
edited September 2013 in Elevation Data
Hello

I searched the forum about handling a big point cloud (in my case 50'000'000) but couldn't find a satisfying answer.

I have an ASCII file with xyz. The data is representing LIDAR data. It is actually a grid 0.5/0.5m with elevation.

I need to crop that data to different polygon area which I created in Global Mapper.

But it is really slow.

Any ideas?

Thanks Rainer

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2013
    Rainer,

    Which part is slow? If you load it in as a Lidar point cloud, select the polygon, then export out to a new XYZ file and choose to crop to the polygon the slow part might be the 50,000,000 point-in-polygon checks, especially if the polygon is complex. Does it have a lot of vertices?

    That said, I have plans to dramatically speed up operations that require large numbers of point-in-polygon tests, perhaps before the final v15 release, which could help if that is the slowdown.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • scrscr Global Mapper User Posts: 42Trusted User
    edited September 2013
    Hi Mike

    I didn't load the data as Lidar point cloud. I opened the points directly as point data. The polygon itself was a test polygon and therefore very small.

    I guess I can do now what I want to do.

    Just to tell you: When I loaded this huge point cloud as points the program slowed down extremly, although the processor time sometimes was idle. For example i couldn't use die export menu because the export submenu didn't show up.

    But anyway, thanks Rainer
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2013
    Rainer,

    Loading that many as normal points would take a huge amount of memory, which probably caused you to swap to disk and everything to get slow. If you load as a point cloud the memory would only be a few hundred MB and it should go quite fast.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
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