Is this possible?

I have never used a laser tracker but it is my understanding that it is possible. Mike Falk that posted here or on POB did that type of work. It is not something that any average surveyor would be equipped to do. The ones that do this type of work don't bother with boundary surveys.

James

That's cheating,?ÿ you edited while I was looking for that video. I don't know about the 0.002" but they are extremely accurate compared to what we do.

A good system can get much tighter that in the right environment.It is also important to note that it's no longer a 'scientific' endeavor.

I'd definitely ask if the spec. is correct or a typo...

0.002 foot/foot is 0.2 feet in 100 feet. So, yes, that's do-able with digital levels and such. This is evidently a railroad bridge. And railroads, especially the high speed kind, have that kind of tolerance. It does take some special effort to achieve it.?ÿ

Posted by: linebender

I am quoting a bridge plan specification. My question: Is it possible to meet, how would you check it and with what equipment? THis is out of my scope of expertise. I'm looking for bridge staking experts. It's a little hard to read.?ÿ The tolerance numbers are?ÿ 0.002" per foot. They are all inch symbols in the spec , not foot symbols.?ÿ

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basically the width of a human hair. Do the specs go on to explain any hairs ?? ?ÿ ??ÿ

Mark, he said those are inch symbols and your post said feet.?ÿ

While 0.2 inch at 100 ft may be possible, 0.010 inch at 5 ft is probably harder with available equipment.

And at what confidence level? "You are 95% confident it was right? We're 100% sure things didn't fit."

The spec is probably wrong, and your comment would apply if it was ft/ft, but he needs to ask.

linebender: Yes this is possible. It tell you that a "?ÿLASER TRACKER OR SIMILAR EQUIPMENT" must be used.

Do an internet search on "Leica AT402?ÿ" sometimes called the Leica Absolute Tracker AT402 and look at the spec. sheet.

I make measurements better that what they want every time I turn on my HP Interferometer (1/1,000,000?ÿ or better in 1.4 meters (or

metre whichever you like).

?ÿ

JOHN NOLTON

Posted by: Bill93

Mark, he said those are inch symbols and your post said feet.?ÿ

While 0.2 inch at 100 ft may be possible, 0.010 inch at 5 ft is probably harder with available equipment.

And at what confidence level? "You are 95% confident it was right? We're 100% sure things didn't fit."

The spec is probably wrong, and your comment would apply if it was ft/ft, but he needs to ask.

You can purchase the equipment to meet (and far exceed) that spec for around 16K. I cant read the print in the op, but it's getting common to see numbers like this.

This would be "precision alignment" that requires special equipment most surveyors do not have in shop.

Mostly used in confined areas and capable of measuring within 1/64 inch.

6 inch stainless mini rule from a prior life in machine room layout.

The tolerance is achievable using MODERN 3D Industrial Metrology techniques. When reviewing measurement equipment data sheets, make sure you pay attention to the?ÿreported confidence?ÿlevel of the data.?ÿ

UPDATE

The plan is to use a FARO scanner to meet the spec.?ÿ Is that possible??ÿ

The tolerance numbers are 0.002" per foot.

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The plan is to use a FARO scanner to meet the spec.?ÿ Is that possible??ÿ

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I suggest you look at the technical data sheet for your equipment. Part of the technical data sheet for ?ÿFARO Laser Scanners you need to consider is ranging error, angular accuracy and 3D position accuracy.

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I'm inclined to laugh at specs like this because what are the odds of the structure settling or warping 5 or 10 or more times that much between the time the measurement is made and or after it's rolled over a couple times by a million ton train.

It depends on the foundation. Our firm works on equipment with foundations that have 20 feet of concrete and pilings to refusal.

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The spec refers to fabrication and then shimming - no mention of machining the working surface. The plates will have a fabrication tolerance of more than is being asked for in the survey.

As noted by BStrand the first traffic over it will adjust everything to suit itself (although the weight of the whole train is irrelevant: it ios the axle loading and the weight on the span which is important.

From time to time we have to set track plates for large carousels used to load undersea umbilical cables - typically up to 5000 tonne on a 40 meter diameter. The plates are all set, shimmed and grouted to around 0.2mm. A full load goes on and everything adjusts itself by up to 0.5mm. Big moving things shape their local universe.

This is our team working on a bascule bridge with a laser tracker