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Norman Oklahoma
Posts: 4749
2,500+ posts
Joined: 5 years ago

I'm going to be adding a 2nd crew to my operation soon and am currently engaged in working up a list of equipment to outfit it. While we do the lion's share of our work with a total station shot lengths rarely approach 1000'.  I am wanting to have 2 prisms (in addition to a 360) for use when running control. I'm thinking that mini-prisms will be sufficient, take up less room in the truck, and cost less.   

But will they negatively impact accuracy? What say you? And what kind of practical range could I expect with one of them and a Trimble S5, for example?

15 Replies
A Harris
Posts: 8402
5,000+ posts
Joined: 10 years ago

Mini prisms are great for close work and setting monuments.

They are difficult to see at a distance and to get a shot on thru any kind of foilage.

I much prefer looking for and at a regular sized prism with a target for anything over 100ft and expecially into the trees and into shadows.

The accuracy is the same with either.

BTW, a second crew will usually cost twice as much as the first crew, it puts you into a whole new bracket when all the costs are put into place.

good luck

Posts: 972
500+ posts
Joined: 10 years ago

The last time I took all my prisms to a calibrated base line the mini prisms turned out to be the most accurate: the  worst, 8mm in 1,475 meters.

Posts: 5861
5,000+ posts
Joined: 10 years ago

If you set the prism constant offset for each prism, any prism should give essentially the same accuracy as another over most of the working range. 

Error will increase if you are stretching the range so the return signal is weak or too close so the EDM is oversaturated. 

The limitation on accuracy should be centering error and temperature & pressure settings.

John Putnam
Posts: 1213
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Joined: 9 years ago

Mr. OK

I went to all mini (Leica) years ago and have never looked back.  Just shot 311m with ATR to one today, no problem.  If you were turning to them conventionally the size might make it harder to see but if you use the magic of robotics then that just is not an issue.  They are cheaper, lighter and smaller and according to Leica, just as accurate as the circular.

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