I bought a nice used Sokkia prism assembly from ebay, The curious part is that it does not produce the same distance as my other prism assemblies, and gets a constant error of 0.01 feet. All of the other prism assemblies are Sokkia, and have been tested on the range.
Since the distance result of is longer by the constant error I tried shimming the prism in the yoke with a washer, and it seems to correct the error.
Is there anything else I could try?
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Historic boundaries and conservation efforts.
I'd glue the washer in and rock on if it's not causing any other issues.?ÿ Sure can't tell from the photo that you did "home mechanix" on it...
That looks like the Chinese knock off sold on AliExpress and Amazon for $38
Years ago Geotronics used to supply a set of shims which fitted behind the prism, so for precise purposes you could take out any instrument/prism constant.?ÿ We used to have the ones which were shimmed marked up with the instrument number, so they didn't get mixed up.
As an aside, I found that the old Kern Prisms used to work OK with Geotronics, but ONLY if they were the right way up! Put them upside down and you got a different reading. We had an old pair of them which were mounted on an inflatable, for hydro work - they were picked up in a junk sale, so it wouldn't have mattered if they had been lost off the back of the boat. (I think they are still at the back of the store, but I dare not go and look for fear of what else I might find!)
Thank you. That is some great information.
Historic boundaries and conservation efforts.