Nikon D7000 User Manual page 11

Display avirtual h orizon based o ninformation fromthecamera
tilt sensor. The reference lineisdisplayed i ngreen when the
camera i slevel.
[I_ Tilting the Camera
The virtual horizon display is not accurate when the camera is tilted
at a sharp angle forward or back. If the camera is unable to measure
tilt, the amount of tilt will not be displayed.
[] Viewfinder Virtual Horizon
If Viewfinder virtual horizon is assigned to the Fnor depth-of-field
_review button using Custom Setting f3 (Assign Fn button) or f4
(Assign preview button), a tilt meter can be displayed in the
viewfinder by pressing the selected button (_ 231).
[] See Also
A virtual horizon can also be displayed during live view (_ 53).
Reference line
245