AT WHAT TEMPERATURE?
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Jon,
We are doing the assembly on the barges simply so we can float it into position and lift it with strand jacks. The strand jacks will be placed on towers that we will construct on the barges. Yes,
it is very heavy. You can keep up with the progress via web can but you should really stop in for a visit!
I posted the requirements just to get thoughts from my fellow surveyors. Many of you thought it was overkill, as did I.
Those of you who mentioned turning off the compensator are in line with my thoughts to collect a little data to satisfy what I have to do as project surveyor.
It is all prefabricated and the fit up is going well.
The trick to a survey like this is to get on the same plane as the structure and break out the simple tools and back away from the fancy stuff. I would be interested in seeing what quality of data a scanner would produce though.
Thanks for all of you opinions fellow surveyors!
AT WHAT TEMPERATURE?
Exactly, makes it tough unless the steel is in a controlled environment.
> Could you meet the accuracy stated below?
>
> "Survey Accuracy: Make precise measurements of horizontal and vertical locations to within +/- 0.01 ft accuracy vertically and +/- 1/8” in the horizontal plane.
>
> Report all elevations, distances and angles on spreadsheet after post-survey processing. Provide copies of field notebooks as well."
>
> This survey is for a 550' long truss span being assembled on 4 barges that are afloat but somewhat moored in shallow water.
>
> Given this information only, how would you respond?
photogrammetry from the barges themselves could provide your individual barge dimensions if they are needed to be individually measured and dimensioned.
also an un-leveled, no-compensator setup with a total station on the barge would do it too.
both methods obviously produce results that are relative to some adopted datum like the barge deck and not gravity. you could also establish points on the barge and monitor them for movement from the river bank so you could also report on the absolute positions of the barges at some average point and also provide an estimate of the range of relative movements.
i hope i got the jist of the problem.
:good:
> > Could you meet the accuracy stated below?
> >
> > "Survey Accuracy: Make precise measurements of horizontal and vertical locations to within +/- 0.01 ft accuracy vertically and +/- 1/8” in the horizontal plane.
>
> > Given this information only, how would you respond?
>
> I think I'd want to find out whether it would be feasible to set up an instrument on one of the middle barges on a bracket attached to the truss. The rest is probably doable with a total station if the vertical angle compensator is turned off.
>
> Basically, you'd establish fixed reference planes and measure horizontal and vertical angles in relation to them (not worrying about whether the zenith angles were measured in relation to actual zenith or not) as well as slope distances. Then you'd compute X,Y,Z coordinates in some arbitrary system and transform them to some more convenient system to make the spreadsheet computations.
I agree Mr. McMillan
> I recall reading several years ago about ship building with total stations. They turned off the level compensation, since the floating ship was constantly swaying relative to gravitational normal, and they would, each day, set up the gun on a pillar and sight two other points to establish the plane, which defined "horizontal on the ship. I'm sure they checked into other points as well, but the leveling was done by lining the cross hairs on a target at a particular vertical angle.
:good:
Assuming this is required after its all together?
Would it be possible to stretch a wire or 2 on each side attached to the truss at each end and measure off that? Could probably align a few intermediate supports to avoid sag. Still be hard to meet those specs, but wouldn't have to depend on a level instrument on a floating barge.
> I agree Mr. McMillan
It may well be, though, that the barge is a stable enough platform that the bracket mounting of the TS isn't necessary. I'd probably incline toward having a simple bracket fabricated just because it's unlikely to cost very much and would be the most stable mounting system that comes to mind.
> Accuracies requests have gotten ridiculous....
The common assumption is that if you set your dc to read out to the some decimal place the resultant measured point will be accurate to the least count. Coordinates listed to the second decimal place usually satisfies the requester of 0.01' precision and all too many surveyors are blissfully unaware of the folly in it.
summer - your Job 1 reminded me of an event from 35 or so years ago. I was a crew chief and my boss told me we had a new job. It was the middle of a winter with a pretty good snowfall, and this job was inside! It involved measuring the existing track at the local University and then marking it with start/finish lines. Boss had quoted $750. The first thing we discovered was that although the radius points were reportedly marked, one was underneath a basketball court and the other was under the hockey rink. Obviously neither was to be removed until their respective seasons were over, and there was an NCAA sanctioned track meet coming up in 3 weeks. We wound up locating a number of points on the inside and outside edges of the track - all with a manual total station and a 200 foot steel tape. No one in the office could figure out what to do with the measurements, so I was charged with completing the job. Once I accepted the fact that the curve radii were unequal and the tangents were not parallel I had a pretty good starting point. One of the track coaches present during the measurements had offhandedly mentioned the NCAA track standards, so I asked the boss if he had obtained these. He had no idea what I was talking about and told me to handle it. After several days of telephone calls (no internet then!) I found a lady who was willing to mail me a copy. This took 10 days, with the track meet looming closer all the time. The info she sent was very detailed, and we learned that virtually all the assumptions we had made about track markings were wrong! I particularly remember realizing that lane dimensions were measured from a certain point in the interior of the stripe, not from the edge. Coupled with small details like this was the fact that they needed both metric and imperial race length start lines marked, with a common finish line. Some start lines were straight lines perpendicular to the lane lines, some were arcs with radius points located so that they crossed the lanes with odd orientations. I think I worked on this (no CAD, no computer) for about 80 hours over 4 days and then went out and marked them all, while the track team was practicing on the track! We finished about 7:00 P.M. the night before the race.
The next week I got to explain to the boss why his $750 fixed fee had cost well over $5,000.
Some years later I heard that the track itself had been disqualified due to the fact that it did not have the require number of lanes. I can't attend or view a track meet without getting a headache, probably the same on I had 35 years ago!!
> Coordinates listed to the second decimal place usually satisfies the requester of 0.01' precision and all too many surveyors are blissfully unaware of the folly in it.
Wait until they inverse between two pair of coordinates and get a different bearing and distance than was written by 0.01'.
