US Patent 7322252 Apparatus for taking measurements in access manholes

An apparatus for measuring the location and annular orientation of pipe inverts and other features in manholes. An elongate, telescoping rod is supported centrally in the manhole opening by a pivot assembly that permits the rod to both rotate in the horizontal plane and pivot in the vertical plane. A laterally-extending foot member on the lower end of the telescoping rod is inserted into the openings of the inverts for measurement. Electronic angle sensors record the length and orientation of the rod member at each measurement point, from which the location and angular orientation of the invert opening or other feature is then calculated.