Determining the difference between two TINs at points of intersections
Jake
Global Mapper UserTrusted User
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
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

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 rightclicking 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 
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.

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 
Frans,
You can calculate the cutandfill volume along the lines simply by selecting one with the Digitizer Tool, then rightclicking and selecting the Measure submenu option to measure the volume. You can specify the cutheight at each vertex of the line then find the cutandfill 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
Howdy, Stranger!
Categories
 12.3K All Categories
 5.3K Features Discussion
 312 Downloading Imagery
 1.2K Elevation Data
 374 Georeferencing Imagery Discussion
 582 GM Script Language
 42 User Scripts
 112 GPS Features
 388 Projection Questions
 790 Raster Data
 1.3K Vector Data
 6.4K Support
 159 Announcement and News
 881 Bug Report
 555 SDK
 1.1K Suggestion Box
 3.6K Technical Support
 523 Other Discussion
 126 GIS Data Sources
 26 Global Mapper Showcase
 217 How I use Global Mapper
 101 Global Mapper Forum Website