getHeightAtCoordinates not work with ImportMesh

Hello,

I have a ground serialize with SerializeMesh() that I save in a babylon file. When I reload this file with ImportMesh:  getHeightAtCoordinates, updateCoordinateHeights, optimize ... does not work.  In fact everything concerning the ground create with CreateGroundFromHeightMap() or CreateGround() is serialized as mesh but can no longer be used as a terrain. We can only edit the properties on the mesh and not the geometry that no longer exists after serialization.

May be missing a serialization for the ground, like serialiserGround() in addition to serializeMesh(). Or convert a mesh to ground after using ImportMesh for used getHeightAtCoordinates. 

Thanks DK