The GDF311 (and the GDF312) Professional 3000 series tribrachs are the mid-grade professional tribrachs from Leica. All Leica original tribrachs comply with the strict specifications and quality standards of Leica Geosystems. Your choice should ideally be made according to your individual accuracy requirements.
These tribrachs are suitable for non-motorised TPS instruments with angle accuracy from 5" to 7" and GNSS antenna stations as well as backsights and control points.
The torsional rigidity (or hysteresis) of the Professional 3000 Series tribrachs amounts to a maximum of 3" (1.0mgon).
The accuracy with which a tribrach returns to its starting position once the instrument has stopped, is called torsional rigidity or hysteresis. This hysteresis is the relative movement between the top plate and the base plate of a tribrach that occurs through the rotation of a TPS instrument. The hysteresis has direct influence on the angular accuracy of the instrument – and that speaks for the original. To optimize the hysteresis as Leica Geosystems has done is complex and calls for the highest precision: a movement of the top plate to the base plate of 0.3µm corresponds to an angle error of 1". Especially motorized instruments with their high acceleration and brake power require tribrachs with very high torsional rigidity.
The foot screws are maintenance free and have a larger diameter. This allows for fine adjustments, even when wearing work gloves under difficult environmental conditions.
WE CALIBRATE ALL TRIBRACH LEVEL VIALS BEFORE THEY SHIP...TRY GETTING THAT SERVICE FROM MOST ONLINE SELLERS!