Determine the plane of intersection between two TIN or terrain surfaces

Summary

Creating contiguous planes/lines of intersection between 3D features can present difficulties when TINs are used as the primary input surfaces. The 'Surface Difference' geoprocessing tool can be used to calculate the geometric difference between two surfaces. The tool performs a comparison between the two surfaces and provides a feature class with three divisions as output.

Note:
This tool requires the 3D Analyst extension.

Procedure

1. Run the Surface Difference tool, which outputs a polygon feature class containing three values: Above, same, and below.
2. Open the attribute table of the polygon feature class and select the record in the table that has a code of 1. These records contain the above features.
3. With this selection, right-click the feature class and navigate to Data > Export Data. Specify an output location for the selection.
   
   

   Note:
   This step requires an advanced license of ArcGIS Desktop.
   

   
   This outputs a polygon feature class and the Feature to Line tool converts the polygon to a line feature class that can be edited to delete non-needed features. This line defines the boundary between the TIN surfaces. This polyline does not contain z-values but can be rendered in 3D space by being draped upon the TIN surface.
   
   **To render the polygon in 3D space, use the Interpolate Polygon To Multipatch geoprocessing tool and skip changing the feature class to a polyline. The input surface for this tool is the TIN with lower elevation values and the input feature class is the polygon exported above.