Vv. Bush et al., DEVICE FOR SIDE LEVELING COMPENSATING FOR NONPERPENDICULARITY BETWEENTHE LEVELING ROD TO THE LINE OF RANGE, Measurement techniques, 37(9), 1994, pp. 1025-1028
A device is described that compensates the nonperpendicularity of the
measuring rod to the collimation surface of the sighting device in lin
e of range observations.