How to read the height mesh?

I want to use the navmesh to performance the collision support for ground, to avoid using much physic collider. And I want to export the data to use in server side.
I found the navmesh I export is not exactly match the ground, and I found an option "Height Mesh" in navigation window.
I want to know is there any way to read the height map from the navmesh?

 

Pretty sure you can't, and also pretty sure you wouldn't want to. Nav meshes are not meshes like you are thinking, they are structured differently. So is the height mesh most likely. So chances are not only would it be much more expensive then physics, you wouldn't even know how to query it because you don't know the structure.

Just use physics it's bound to be simpler and perform better.