Question about scale of imported heightmaps

How is the scale of an imported Landscape determined? I have a heightmap of a 4096m x 4096m area. How do I make sure it has the same size if I load into UE4? Is it simply 1 pixel of the heightmap = 1m in unreal?​

Yes. 1px=1m

Height is a ratio. Look in the docs since we got them to update them with sample formulas.