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Elevation Grid Creation Options

StacyL
StacyL Global Mapper UserTrusted User
edited January 2014 in Elevation Data
Hi Mike,

In GM 15, there is now an option box for "Automatic Spacing Multiple of Point Spacing".
It seems the "Help" page has not been updated to explain this option.

Can you explain this option?

Thanks,
Stacy

Comments

  • global_mapper
    global_mapper Administrator
    edited January 2014
    Stacy,

    The new option refers to how large grid cells will be when using a new bin gridding method on Lidar point clouds. A native point spacing is calculated for Lidar point clouds to represent the average distance between point samples. The 'Automatic Spacing Multiple of Point Spacing' means that the grid spacing will be some multiple of that calculated point spacing. So if you used a value of '3' for the spacing and the points were calculated to be on average 0.5m apart, the grid would have a spacing of 1.5m. Typically a value of 3 or so is good for gridding dense Lidar point clouds.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • txrpls
    txrpls Global Mapper User Trusted User
    edited January 2014
    The new option refers to how large grid cells will be when using a new bin gridding method on Lidar point clouds. A native point spacing is calculated for Lidar point clouds to represent the average distance between point samples. The 'Automatic Spacing Multiple of Point Spacing' means that the grid spacing will be some multiple of that calculated point spacing. So if you used a value of '3' for the spacing and the points were calculated to be on average 0.5m apart, the grid would have a spacing of 1.5m. Typically a value of 3 or so is good for gridding dense Lidar point clouds.
    Mike,

    Should this match the value use for the spacing when auto classifying ground points?

    Mark
  • global_mapper
    global_mapper Administrator
    edited January 2014
    Mark,

    Yes they refer to the same thing, but the best value to use may not be the same for gridding vs. automatic classification. The classification does grid internally at different resolutions, starting with the specified one, so you can speed up the classification by specifying a larger bin size. It's pretty dependent on the actual characteristics of your point cloud though and a bit of an art more than a science sometimes :)

    Thanks,

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