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Prism compatibility for total stations

Prism compatibility for total stations

Prism compatibility for total stations

I recently acquired an older total station (Wild Heerbrugg / Leica TC 1000) that I would like to use to do some occasional topo surveying and construction staking.
I don't have a prism or prism pole.  So my question is, are only certain models/kinds of prisms compatible with my instrument in order to get an accurate distance measurement?  Will using the wrong prism give me incorrect distance readings?  Does my instrument need to be calibrated to the specific prism manufacturer/model somehow?  Or will any decent prism make/model be accurate?

(No manual with the instrument, so if anyone knows of a good source of old equipment manuals that would also be helpful.  I found this site:  www.surveyors.de - which has the manual in Spanish as a free pdf download but not in English.


RE: Prism compatibility for total stations

What you're referring to is usually called the "prism constant" -- how much is added/subtracted to/from the immediate distance measurement before the result is presented to the user.

Yes, you can use different prisms (from other manufacturers) and get good results. However, different manufacturer's instruments do have different assumptions about how much should be added/subtracted for each measurement, so different prism constants do need to be applied when mixing prism and total station models.

Your best bet is to
(a) make several measurements over known baselines -- comparing what your instrument says and what you know from tape measurements, and
(b) learn how to set the appropriate prism constant in the total station.

RE: Prism compatibility for total stations

hi boss ,
  there will b noproblem in using any prsim of any instruments u just make sure that the prism rod is not cross r its length is not accruate
just try it

RE: Prism compatibility for total stations

The TC1000 can use any reflector you like.
Wild has from the very beginning used a standard round prism as a reference and this instrument must be set to a prism constant of zero for this standard round prism. (type GPH1 or GPR1)
This prism has an actual (true) prism constant of -34.4, which allows it to be put centred onto the pole avoiding errors when it's not exactly pointed right.
As a consequence you need to set the prism constant to:
 +34.4 for a true zero constant prism or reflective sticker
 +17.5 for mini prisms (GMP101/102) as are used commonly in construction and monitoring
 +30.0 for 360 mini prisms (GRZ101)
 +23.1 for 360 prisms (GRZ4)
The mentioned types are from Leica, but other prisms will work just as well, just make sure you set the constant correctly in the instrument.

You might try http://www.wild-heerbrugg.com for obtaining a printed manual for the TC1000.
Manuals for almost any other total station from Wild / Leica Geosystems explain the required prism constant settings.

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