Abstract: Apparatus and method for measuring height variations along a directional axis in a roadway surface from a vehicle includes a first sensor for sensing a first distance from the first sensor to a first point on the surface and generating a first signal indicative of the first distance; a second sensor for sensing a second distance from the second sensor to a second point axially separated from the first point on the surface and generating a second signal indicative of the second distance; and a computer for receiving the first and second signals and generating and recording a difference signal indicative of the difference in height of the first and second points, The first and second sensors are operated simultaneously to compensate for vertical motion of the sensors with respect to the surface.