I have been looking a tribrachs recently and just wanted to reach out to see if any one has used a bi-directional plummet tribrach? Is adjusting them done differently? Are they more susceptible to being knocked off plum? Is trimble the only one that manufacturers them? Also what tribrach models do you suggest for the following:
1. GNSS
2. Backsights
Does bi-directional mean that it has the eyepiece on the side and also works with an instrument or prism adapter that looks straight down through it?
My Topcon tribrachs allow a partial view straight through, maybe just over half, but I don't know if it is enough to work with.
Yea, the one I was looking at is for a Trimble SX10 but is compatible with S Series Instruments. I have Topcon tribrachs as well, but I guess I never tried it.
"Also what tribrach models do you suggest...."
The Leica Professional models (GDF321 &GDF322). They cost a bit more but worth every penny. There is no equal.
Don’t use optical plummet tribrachs.
For easier accuracy checking, use open tribrachs and the plummet or laser in the instrument. For prism mounting or GPS use adapters (“carriers”) with plummets. The best optical plummet adapters by far are Leica GZR3. They are solidly made, and the central bubble stays centered as you rotate it. Leica SNLL121 laser plummet adaptors are also nice. Leica GZR103 are inferior, with a reversed view through the plummet and a bubble that needs frequent adjustment. Some Chinese copies on eBay are actually better made, with a non-reversed plummet.
If you need to use a 5/8 threaded GPS or non-Leica prism on the Leica stud; use the GAD31 adaptor, or the slightly better made Chinese copy.