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Total Station Precision

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bill93
(@bill93)
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People often forget how much averaging it takes to get angles accurate to the instrument spec. The definition isn't intuitive.

https://s3.microsurvey.com/support/Knowledgebase/stderr/Din18723.pdf

 
Posted : October 2, 2024 12:14 pm
field-dog
(@field-dog)
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Topic starter
 

@ BStrand

Looking through my state’s standards, I found only one line relating to locating or setting a monument with an instrument.

7.(f) Side ties to locate or set a monument shall be substantiated by multiple measurements.

 
Posted : October 3, 2024 1:09 am
Norman_Oklahoma
(@norman-oklahoma)
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If the boss is willing to pay the extra bucks and get the 1" model then I see no big reason to oppose the purchase. They operate the same as the 3" and 5" models. And it is usually not all that much more in the grand scheme of things. If that is what it takes to maintain peace and harmony, go for it. Choose another hill to die on. Use your political capital to push for high end tribrach, tripods, glass and rods instead.

 
Posted : October 3, 2024 1:12 am
OleManRiver
(@olemanriver)
Posts: 2542
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So true. Now some manufacturers quote the same 3” angle but is is done by different standards DIN or ISO. And that makes a difference as well. In how one obtains or goes about the field observations.

 
Posted : October 3, 2024 1:15 am
(@bstrand)
Posts: 2359
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My coworker is concerned about a possible future court case where a judge might rule against us for not using a precise enough total station to set the property corner in question.

Like one of my golfing buddies says when people blame their clubs for bad play-- it's the indian not the arrow. 😆

I've never studied it but I'd bet humans are far and away the biggest source of error on any given survey.

 
Posted : October 3, 2024 1:33 am

Norman_Oklahoma
(@norman-oklahoma)
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"I’ve never studied it but I’d bet humans are far and away the biggest source of error on any given survey."

People end up in court because of blunders, not because of missing precision targets.

 
Posted : October 3, 2024 2:12 am
not-my-real-name
(@not-my-real-name)
Posts: 1081
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I agree. The judge won't be taking your equipment choice into consideration.

Historic boundaries and conservation efforts.

 
Posted : October 3, 2024 2:34 am
MightyMoe
(@mightymoe)
Posts: 9988
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If you're using the instrument for fill in then the 5" gun is good. If you need to run a bit longer traverses maybe the 3" gun, if you need to do huge traverses and extra precision work the 1" gun would be handy. But who does huge 20-30 mile traverses anymore, I sure don't. I'm assuming you're not laying out precise building construction.

It sounds like the 5" gun will work well for your purpose. Get the 3" gun and you will never need to worry about it. The 1" gun is too much.

 
Posted : October 3, 2024 3:19 am
MightyMoe
(@mightymoe)
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The other question is why are they worried about ending up in a court case because of using a 5" instrument to set property corners?

That's exactly the type of instrument made for that purpose.

I've never even heard of a surveyor having that issue come up in a court case, maybe if anyone wants to look it up give it a shot. It's probably one of those things that will take forever to find cause it didn't happen.

 
Posted : October 3, 2024 3:51 am
field-dog
(@field-dog)
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@ bill93

I enjoyed reading the article. So much good information. I remember in 1994 when I moved from a theodolite to a total station, I was trying to compare the absolute encoders (diodes) on the total station’s plate to the etched graduations on the theodolite’s plate. It’s still a physical plate and is subject to inherent imperfections from the manufacturing process and to temperature variations.

 
Posted : October 3, 2024 4:26 am

(@dmyhill)
Posts: 3082
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People often forget how much averaging it takes to get angles accurate to the instrument spec. The definition isn’t intuitive.
https://s3.microsurvey.com/support/Knowledgebase/stderr/Din18723.pdf

And...(I was told) that they used to build the gun to make a certain spec and basically sorted them at the factory based on how they turned out.

Now, the precision is determined by what you purchase. All the guns are 1" and you pay them to not dither the results out to 5". So, in practice, in the past it was common for an instrument to exceed the stated accuracies, but that is no longer the case (according to some of the reps I have spoken to).

Yeah, a lot of caveats there, so, I would like to see an update to this article...

 
Posted : October 4, 2024 3:37 am
(@lukenz)
Posts: 525
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If you don't want to fork out for star*net but have time on your hands the government agency here responsible for survey matters has https://www.linz.govt.nz/products-services/geodetic/geodetic-software-and-downloads/geodetic-software/snap-and-concord-downloads which is free to use.

Tutorial here https://www.linz.govt.nz/products-services/geodetic/geodetic-software-and-downloads/geodetic-software/snap-guidance

 
Posted : October 4, 2024 11:21 am
(@crashbox)
Posts: 542
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I remember years ago in a PLS refresher course (long before I actually had my license) where we calculated the number of angle sets we would have to turn to get a desired accuracy of ±1" per DIN 18723. The results of that persuaded me that a 3" or better gun was the best fit for me, considering instrument cost and type of work I would eventually do. And my comfort level remains at a 3" or better TS.

 
Posted : October 5, 2024 1:15 am
field-dog
(@field-dog)
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Topic starter
 

@ lukenz

Thanks for posting the links.

 
Posted : October 5, 2024 5:22 am
(@cvt)
Posts: 9
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Equally as important as the accurcay of your instrument is taking the time and admittedly the expense to have it calibrated on a regular basis. It will be an inconvenience to be without it for the time needed but these are the tools we use to make a living. Maintainenance of instruments, rods and tripods is a better investment than increased accuracy.

 
Posted : October 7, 2024 2:35 am

(@bstrand)
Posts: 2359
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And…(I was told) that they used to build the gun to make a certain spec and basically sorted them at the factory based on how they turned out.

I think that's basically how CPU manufacturing is handled as well.

 
Posted : October 7, 2024 4:53 am
(@minbarwinkle)
Posts: 73
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Having a better instrument, 1 sec vs 5 sec, will give you higher confidence in your work and it will be more versatile in the long run.

I'm just speculating here, but I would say that a higher accuracy instrument will hold its value better than the lesser alternative.

Here is Australia, you need a 1 sec instrument if you intended to do any serious infrastructure work, it's a spec requirement. If you ever want to do monitoring, a 1 sec instrument is, usually, the standard requirement.

You might only do boundary work for now, but if the economy goes south, you might have to look for work wherever you can find it and having a better instrument gives you more options.

 
Posted : October 9, 2024 2:33 pm
(@eleven)
Posts: 4
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1” total stations are overkill at best (Unless you’re providing monitoring surveys and services on the regular). Field procedures are FAR more important than the difference between a mean angle of 1” vs. 3”. Turning a minimum of 5 sets of angles for control will tell you an amazingly accurate story. Modern robotic total stations are incredibly accurate at turning angles.

And maintenance - OMG. Plz don’t put a 40k+ total station on a cheap tripod, unadjusted tribrach and for the love of accuracy, purchase quality prisms. Put the extra $$$ you would have spent on a 1” total station it into all the parts and pieces that are vital to accurate surveying.

Also, send that total station in yearly or more as needed! We provide loaners for our RTS units while the customers is in the shop. No downtime.

 
Posted : October 9, 2024 3:10 pm
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