US Patent 7266897 Self-aligning, self plumbing baseline instrument

A self aligning baseline instrument including a first light assembly operable to generate a first vertical light plane, a second light assembly operable to generate a second vertical light plane at a predetermined angle to the first vertical light plane, a third light assembly operable to generate a first horizontal light plane that is perpendicular to the first and second vertical light planes, and a fourth light assembly operable to generate a vertical plumb light beam that defines a reference point on an underlying surface, the vertical light beam parallel to and coincident to the center axis of the instrument. The first and second vertical light planes and fourth plumb laser beam all intersect together through the center axis of the instrument.