# Determining the difference between two TINs at points of intersections

Global Mapper UserTrusted User
edited October 2012
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

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
• 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.
• 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
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