@ bill93
Put some distance numbers on the angle value.
At a distance of 200' a 5" angular error would only produce a linear error of 0.005'.
Please explain how total stations are rated in terms of arc seconds.
I would not hesitate to use a 5” gun. Most states regulations are still written in a way that a 20” theodolite or transit could achieve the angular requirements and then throw in a chain or steel tape one can still meet 1:20000 precision if correct care and procedures were used. Now I like .5” and 1” angular and 1mm +1ppm edm but that’s my geodetic side . Of course like others have stated that tight instrument is useless on bad tripods and glass tribrach and glass and rod.
I was handed a small traverse to adjust a few days ago. The loop did not meet requirements. I was lucky as they discovered the tribrachs were out of adjustment. As they traversed throughout the site to do the Topo. They made enough cross ties and such that I was able to save a complete re run of the loop all of that was done after they fixed the bad tribrach.
Redundancy always helps. For a 3” gun 4 rounds gets you down to like 2.4” depending on how the gun is specked though.
@ Norman_Oklahoma
IMO the sweet spot between precision and cost is the 3″ model.
That sounds reasonable.
@ dmyhill
Are you shooting to a rod with a circular bubble?
We use a rod with a built-in circular bubble.
@ dmyhill
I want to see that court case.
There was no court case. 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. I know that sounds ridiculous, but it's true. He's using this reasoning to say we need a 2" or a 1" second total station to set a corner that won't be disputed because we'll set it with 2" or 1" precision. Oh boy. The knowledgeable will prevail. I'll write a paper with a list of our typical jobs, the state requirements for precision, and the equipment we should have. Florida's minimum technical standards have changed, so if no precision is indicated I'll just show the math. You can't argue with math.
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
@ 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.
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.
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.
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.
"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.
I agree. The judge won't be taking your equipment choice into consideration.
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.
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.
@ 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.
