Global Mapper v25.0

Adding elevation to LiDAR data

nikolajvh
nikolajvh Global Mapper User
in Elevation Data
I have a Surface that defines the height limit of my terrain and object like buildings and trees.
I also have a LiDAR scanning of the area.
I would like to extract the LiDAR points that penetrate the limitation surface.
As the height of the limitation surface vary, i can not just extract the points above a specific height.

My possible solution is to make a DEM surface of the limitation surface with inverted height and ad it to the LiDAR height, and the points with > 0 elevation is above the limitation surface. Then i can classify the points and reverse the process.

But when i try to add/extract an elevation from lidar points the elevation values is multiplied by 100.?
So when i add 50m an elevation will become e.x. 218.95m x 100 +50 = 21945m

I have tried with multiple LiDAR sets with the same result.

Any one know how to add elevation to LiDAR correct or have another way to accomplish this task?



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Answers

  • csnoke
    csnoke
    Is this for obstruction analysis? There is no good way to do it currently, all methods approximate the obstacle and OIS surfaces.
  • 946
    946 Global Mapper User Trusted User
    Maybe this way:
    Export the lidar data as csv file.
    Load back into GM.
    Change attribute value ELEVATION with other name.
    Apply elevation to the points from the obstacle limitation surface DEM.
    Use calculate attributes over the csv layer and extract original elevation from DEM elevation.
    The negative value is penetrating the surface.

    Or create 2 surfaces.
    one of the lidar data and second of your limitation surface.
    extract with combine/compare terrain 

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