FPM FG-OLN Optical Nadir PlummetThe small optical plummet FG OLN with Wild Leica Claw system from FPM is for the exact positioning above reference points. The FG OLN is a small optical nadir plummet with an axis system that can rotate freely. Two bubble levels are used to level the instrument. The adjustable bubble levels provide a sensitivity of 2 arc minutes per 2mm bubble travel. The advantage of the FG OLN compared to tribrachs with a built in optical plummet is that the user