In 2001 I had to survey a bunch of column tops on the roof of a large urban mall, they wanted to fabricate steel to place on top of these columns, which protruded from the roof, to build a building or something on top, I don't remember what exactly.
It was someone else's project, but they asked me to help. At the time, I had a Zeiss S10 (1", 1 mm+ 1 ppm), and they had a Topcon GTS 3B. What we wound up doing was shoot all with both instruments, and also RTK (mainly to get good orientation and position), and also tape between the columns with a calibrated steel tape. I came up with weights for each type of observation, and threw it all into a least squares adjustment. Then I transformed to a local coordinate system at the surface.
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Fascinating post. Getting highly accurate results is something I'm always curious about. Now I'm wondering about this though:
1" in 100' is 0.0004848'. 1" pointing is rather hard to do in outdoor environments, especially on construction sites. If you used robotic aiming, though, and took a lot of wrapped shots, say 10 per interior angle, you could achieve this easily. - See more at: http://beerleg.com/index.php?mode=thread&id=276429#sthash.sLHNQQ15.dpuf
How exactly does wrapping work? I'm not sure what this means. I usually do topos and construction staking, so this is outside of my expertise, but I'm trying to broaden my horizon.
Anchor Bolts
Ancor Bolts are a problem becasue the tolerances are soo tight that it is hard not to use up your error budget in plumbing the prism over the ancor bolt or your back site. This is a handy tool that I have found that should help with that issue.
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Goes like this:
Doesn't look like these guys were going for ultra accuracy, though, given the speed with which he is aiming.
I wish they would have shown the accuracy residuals where you could read the screen.
Also, I think pretty much all data collection programs show 1 sigma resection results.
I wouldn't want to use Carlson with Trimble, but what do you mean by your statement?
Carlson SurvNET is on quite on par with StarNet these days. I took a seminar taught by Bruce Carlson and Dean Goodman on SurvNet. If I wasn't so deep in Trimble it's the way I would go. I wonder how their GNSS processing software is coming along?
Also "wrapping" is slang for measuring multiple sets of angles. Redundant measuring is one of the keys to increasing accuracy/precision.
tell the contractor that's what grinders are for.
Anchor Bolts
> Ancor Bolts are a problem becasue the tolerances are soo tight that it is hard not to use up your error budget in plumbing the prism over the ancor bolt or your back site. This is a handy tool that I have found that should help with that issue.
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So have you used the Marksman?
You like?
Worth the cost?
Anchor Bolts
We just bought 2 of the Marksman, one for a back site and one for a foresite. We need to see over a 3 foot tall guard rail. With the Marksman and a section of range pole, we should be able to plumb a prism over a point with a +-0.0005 meter accuracy. We are going to start on 2 pillars and tie the points from both pillars, along with 2 tripods, then reshoot the points from the tripods, then tie into 2 more pillars, and reshoot the points from there, along with the other pillars. The Marksman should allow for a quick repeatable set up. The first time, we are going to shoot a point, then rotate the Marksman 180 degrees, re level, and shoot the point again. We will be using a Leica TCRP 1201+ and turning 4 sets of angles. We are only going to have to tie 8 points for now. These are alignment marks on a navigation lock. I hope that the error ellips is less than 0.005 meters. After we do the initial survey, we will check to see if we have too much redundancy and can speed up the process. One of the Pillars will be in a secure location, and I plan to have an OPUS X90 running on it for several weeks to prove that our pillars are stable.
Anchor Bolts
> With the Marksman and a section of range pole, we should be able to plumb a prism over a point with a +-0.0005 meter accuracy.
I would expect a significant amount of eccentricity due to the range pole addition -- any slop in the concentricity of the 5/8"x11 thread will affect the alignment. But if you turn the Marksman 180 and reshoot, the mean should be good. Half-millimeter plumbing accuracy is an ambitious goal, though. I'm interested to learn what you find out, so I hope you'll post results.
Anchor Bolts
Excellent response. I look forward to future reports on this project and other users of the Marksman. It is on my wish list.
Anchor Bolts
Steve, man, don't forget to close that red case, dust will get in, then in the instrument, then you won't be able to chase these millimeters...;-)
