Global Mapper Pro

Determining the difference between two TINs at points of intersections

Jake
Jake Global Mapper UserTrusted User
edited October 2012 in Elevation Data
Is there an easy way to determine differences between 2 TINs? Right now this is what I tried.

Convert TIN areas to lines.
Intersect lines and place vertices at intersections.
Individually look at the Z value of the line vertex at the intersection (there are hundreds of thousands).

Ideally I would like to find the intersections and the difference for all points. I can do this with combined grids (subtraction) but I am trying to avoid using grids since the data is irregular (some points are close, some are far apart). Given the quantity is there a way to automate this? That is create a 3D point layer with the Z values?

Thanks

Comments

  • global_mapper
    global_mapper Administrator
    edited April 2012
    I think you would almost have to use grids to do this kind of difference operation since a TIN is really a surface and not just difference at points (unless the TINs have exactly the same triangles, just with different Z values). Once you grid the TINs and then find the subtraction surface, you can then create 3D points from that subtraction surface by right-clicking on it in the Control Center and selecting the option to create 3D points from the grid cell centers.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • Jake
    Jake Global Mapper User Trusted User
    edited April 2012
    OK thanks. Basically that is what I have done. However, since the point density varies significantly using a grid is not optimal. Either it is too coarse a grid or too fine, depending on the area you are looking at. For now I will use the combine subtraction and export the 3D points.
  • Frans
    Frans Global Mapper User Trusted User
    edited October 2012
    Hi Mike,

    I'm sure MP14 can make volume calculations but I can't achieve it.

    I have a layer of ASCII data over an area I want to excavate. I've created an elevation grid with that. Then I have created a design including toelines and slopes and dilligently alocated elevation levels to each line as well as x,y in UTM coordinates. How can I get MP14 to calculate the volume to excavate?

    Thanks

    Frans
  • global_mapper
    global_mapper Administrator
    edited October 2012
    Frans,

    You can calculate the cut-and-fill volume along the lines simply by selecting one with the Digitizer Tool, then right-clicking and selecting the Measure submenu option to measure the volume. You can specify the cut-height at each vertex of the line then find the cut-and-fill volume along some corridor around the line relative to your terrain surface.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
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