For Sale - Leica precision traverse set
Leica precision traverse set for sale. Traverse set includes:
2 GDF-21 tribrachs (near new condition, slight scuffing of the 3 pads on the bottom of the tribrachs)
1 Wild Heerbrugg GZR3 precision carrier with optical plummet (very clean with 2 small paint chips)
1 Leica GZR3 precision carrier with optical plummet (very clean with 3 small paint chips)
2 Leica GPH1P precision prisms (near new condition with only a "1" and "2" scribed on the back of the prisms)
2 Leica precision targets (I can include 2 shields and 2 lights for night or underground work)
1 Leica orange traverse case
The two tribrachs are light green in color. The two GZR3 carriers are the classic Wild green in color. I purchased the GPH1P prisms from a New York surveyor who used them indoors. One of his industrial measurement projects was highlighted in a Professional Surveyor Magazine feature article (March 2009 issue).
Photos available upon request via PM or email c e kooper at gmail dot com
Some photos. The only marks on the prisms are numerals "1" and "2" etched on the backs to allow tracking of the two prisms during a traverse.
The prism have a locking screw that fixes the prisms in horizontal positions. I also conducted a test to check the offsets of each prism + carrier that I can forward to anyone interested in the traverse set.
Bumping this to the top as an interested party turned shy. One of the things they expressed an interest in is whether I had a Wild ZNL plummet to go with the traverse set. I don't have a ZNL, but do have a ZBL that I will sell with the traverse set.
The Wild ZBL is both a zenith and a nadir plummet. There is a knurled knob at the front of the plummet that switches between the two modes (see photos below). The plummet comes with a Wild tribrach with fisheye bubble and a leather carrying case in good condition; no dry rot. There are two plate bubbles set at 90° to each other. While it comes with a tribrach, the plummet will fit in any Wild/Leica tribrach. My main use for it is to plumb under mine spads when doing underground surveying and for accurate setups at calibrated base lines.
The ZBL plummet has a published accuracy that lies between the GZR3 precision carrier and the Wild ZNL and the scope is 10x. The accuracy is 1:10,000, while the GZR3 is 1:3000 (0.5mm in 1.5 m) and the ZNL is 1:30,000.
Tighter manufacturing tolerances, I suppose. The chinese things can be out of adjustment the minute after you put the donut away. The good Leica ones will stay in adjustment, with normal use, just about forever. Less racking in use. There truly is a difference in the results.
"Convention is like the shell to the chick, a protection till he is strong enough to break it through." Learned Hand
The new owner has projects that require tight tolerances, so this precision traverse set will work well for them. One of the unique features of the prism glass is that it is not coated. Reflection back to the instrument is avoided by having the face of the glass be at a slight angle to vertical. The prism housing is made from aluminium! 🙂
I used to do conventional control surveys, but there isn't much call for those today. The only thing I was using it for lately was measuring distances between intervisible GPS control stations so I could throw some conventional survey measurements into Star*Net or Columbus along with my GPS observations.
Using a Leica DI-2002 Distomat with published accuracy of 1mm +/- 1ppm and static observations with my legacy Leica SR530s with published accuracy of 2 to 3 mm (they may be boat anchors in 10 days), I was able to get mark to mark distances of the two to agree within 1 to 1.5 mm in a baseline of 1100 feet. I decided to sell it because comparing distances between GPS control points wasn't enough to warrant keeping them. I know the new owner will enjoy using it while I sob into my glass of prune juice. 😀