What does interpolate tangent to edge mean?

[cbucks]

What do these two checks do? I looked at the help and don't really understand curious if someone has a better explanation.

 

 

[Alaskan_Son]

When you choose to Interpolate Tangent to Edge, Chief attempts to build the terrain so that the resulting terrain contours have curvature that is more tangential to the elevation region.  In other words, if viewed in a perpendicular cross section,  the terrain arc would be tangent to the flat line created by the elevation region. The results vary a bit depending on how extreme the terrain slope and on your Terrain Surface Smoothing and Triangle Count settings, but here's an example to help highlight the difference with my settings pretty well maxed out for effect...