Geomax Prism Reccomendations

Full disclosure, I have no experience with products for either of these manufacturers, that being said I don’t think that you will have any issues.

If you are simply looking to track a passive reflector the type of reflector doesn’t terribly matter
(in my experience). I’ve run both Leicas and Trimbles with a variety of passive prisms and never noticed a difference in the ability to track as long as the glass stays visible to the gun. (And is the shiniest thing in sight.)

If you were looking to upgrade the Leica MPR122 is, for my money, the best 360 prism out there, with better repeatability than the GRZ4 (which Leica is transparent about in their specs).

As far as the copper/silver proprietary coatings, that depends on what precision you are hoping to achieve. It you are employing a 360 prism I assume that we aren’t splitting millimeters here. And if you are looking to get precise, I am of the opinion that one nodal prism is as good as the next (with regards to mini/layout prisms). When it comes to backsight/traversing setups your tribrach plummets, centering on components (tribrachs-carrier-reflector), pointing to the station, etc are more likely to be sources of error than whether or not the reflector has a coating.

As long as the prism constant is set correctly, any brand of prism works well enough. Test them all at a known distance to be sure you have it right. The internal reflective coating being silver or copper is no big deal, it might affect extreme range a little but has no effect on accuracy. The external anti-reflective coating is also no big deal, it might affect accuracy at very close ranges if the prism is in nearly impossibly perfect alignment.

However, the Leica style prisms (either genuine or copies) have several advantages that are worth the upgrade:

1. The quick connect system is convenient and puts every prism at the same height every time, which will match the graduations on a Leica rod and match the total station axis height when using a Leica tribrach adaptor.

2. The Leica style 360 prism has less offset than other brands when rotated. (I still don't recommend any 360 prism for traverse or other important shots)

3. All sizes of Leica prisms are nodal. (Just be careful with the prism constant setting because they are not labeled the same way as other brands.)

4. The GMP101 mini prism is well made and can replace the larger circular prisms for most all uses.

I'd like to hear how you are enjoying your new "Leica" vs. your experience with Topcon.

You can use any prism, including the APT1, with any instrument. Just be sure to account for prism constant. Leica calculates prism constants differently than other manufacturers. I'm not sure if that applies to the Geomax and Carlson brand varieties or not. Test and be sure.

Other brand prisms will work, but Leica prisms are very high quality. When using a Topcon Robot I noticed that the Topcon tracked the Leica GRZ4 noticeably better than it did the APT1 it came with. Possibly not enough better to justify the $1200 price of a GRZ4, but probably enough to justify the $400 difference between that and the APT1's asking price.

Dittos on the GMP101 minis. A lot of capability in a small package. I haven't found their maximum range yet. Probably it is less than that of a full size Leica prism, but a great deal more than anything I would attempt with a total station while I've got an RTK setup on hand.

I run a Geomax Zoom90 and I use all Lecia accessories. I much prefer the Lecia GMP101, lighter, cheaper and more accurate than a 360°. I've got two, one for pole and one for back sight to eliminate prism constant errors. Also, Leica legs are far superior to anything else I've seen/used and make a difference to final precision.

If the site is open I'll be using GNSS so total station is to get shots around buildings etc. and not that hard to keep prism pointed at total station if you need to. Same on a construction site, 360° isn't going to track you any better when a machine comes on line for you walk behind a pile of material.

I'm definitely liking the new instrument a lot compared to the Sokkia. My main complaint about it was the tracking. If I lost line of sight, the instrument would just be lost and looking into space. It was just frustrating and time consuming working with it. The Power search on the new instrument works great and it does everything it's supposed to do! I'm impressed so far and look forward to using it at more of a capacity once I trust that the prisms that I'm using are satisfactory.

I straightened the prism constants out already. But the more research I do on the prisms, the more questions I have! In an ideal world, I would just be able to stay with the prisms, prism pole, and tribrachs that we already own. However, I'm not willing to sacrifice too much precision or leave myself open to any inconsistencies like the ones that Leica says could happen at close range due to the lack of the copper anti-reflective coating or other reasons. I'm not trying to split mm's but would like to be able to stake out to the hundredth. I'm mainly doing property surveys, subdivisions, construction, staking out foundations and pinning footings, large commercial properties, ALTA's, Taking and Layout Plans for Municipalities, etc...stuff like that.

You don't need to worry about the coating on the 360 prism, it's unlikely that you will collimate with the glass surface, given the angle it's at. The Nodal prism, just point it slightly to one side of the instrument when closer than 20m. The issue with collimation usually only occurs at distances closer than 20m. We use Sokkia nodal prisms with a Trimble SX12, never had a problem with accuracy.