Steve, Marvin,
There is a bench mark shown on the existing plot plan. But no bench mark at site to co-relate. The surveyor needed 2 ref points. I asked the surveyor to take a pump suction line as the reference point. I have a check tape measure of the dist between the suction and discharge, which happens to be off by 140 mm from the GPS measure. Yes, a transmitter was used at the survey points.
Perhaps, the pump is not where it is as shown on the drawing. That is a big as-built error, then.
I will post here, if I come to know anything more about this.
Sajit
-----Original Message-----
From: Marvin Punu [mailto:marvin_pnu@yahoo.com]
Sent: Sunday, October 31, 2004 10:16 AM
To: <a href="/group/PipingDesign/post?postID=dlq7V8B6VL8dMcJ-SZYGeRLsRPtjs8VAx9kNXdqkSny9RCtVerCEgZGn3Hvw-S9gPpaV-qwh_egNF2avZyDu_8_h">PipingDesign@yahoogroups.com</a>
Subject: RE: [PipingDesign] Survey vs FFWs
The GPS shall be calibrated with the local bench mark (should be available at site) before use.
Problem seems to be related with calibration, otherwise results of GPS survey are generally good.
regards
Steve McKenzie <mechproj@xtra.co.nz> wrote: Hi Sajit
a GPS is a fairly broad description. For 2cm accuracy, the surveyor would be using local transmitters. I suspect he measured the wrong pipes or got his identification table messed up. I wouldn't waste your time suing him; it will cost too much. However his mistakes may produce a valuable lesson if you can sit down with him and figure out what went wrong. That way you may be able to use a very powerful tool (GPS) with confidence in the future. If you walk away, you have learned almost nothing and paid a high price for it. If you figure out the problems and how to overcome them then you are one step ahead of the rest.
I would be very interested to hear how you get on.
Cheers
Steve
-----Original Message-----
From: Sajit Viswan [mailto:sviswan@tebodin.co.om]
Sent: Saturday, October 30, 2004 10:14 PM
To: <a href="/group/PipingDesign/post?postID=dlq7V8B6VL8dMcJ-SZYGeRLsRPtjs8VAx9kNXdqkSny9RCtVerCEgZGn3Hvw-S9gPpaV-qwh_egNF2avZyDu_8_h">PipingDesign@yahoogroups.com</a>
Subject: RE: [PipingDesign] Survey vs FFWs
A survey was done by the pipelines survey team with the piping designer present to show the center line of the pipe etc. The survey used the GPS instrument. The surveyor claims a accuracy of the reading of 2 cm. However there was in-accuracies of the order of meters. I still have not figured out what went wrong there. Perhaps have to go with the tape rather or trust the fabricator to measure it up again before he makes it.
Sajit
-----Original Message-----
From: Paul Bowers [mailto:pbowers@pipingdesign.com]
Sent: Saturday, October 30, 2004 8:00 AM
To: <a href="/group/PipingDesign/post?postID=dlq7V8B6VL8dMcJ-SZYGeRLsRPtjs8VAx9kNXdqkSny9RCtVerCEgZGn3Hvw-S9gPpaV-qwh_egNF2avZyDu_8_h">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] Survey vs FFWs
Never trust a non-piper's field dimensions. Often you will get dimensions to the outside of insulation, wall surfaces (unrelated to building columns) and "that thing that looked like a good reference point".
Try to not get locked into anything, this sounds like one of those neverending projects.
Put an experienced guy on site, someone that can talk to the operators and contractors.
If "add more FFWs" is the solution to all problems, suggest that they hire an artist to draw a picture and have a contractor build from that. This often actually works if nobody cares about specs.
Paul
> Our project is a refinery modification type of work, a servey
> contractor provides field survey service for us. They've surveyed
> piping, equipment, piperack, foundation... and not surprisingly
> almost all the survey results were out from couple inch 2 couple feet
> (not kidding). But after a long still going argument about how to
> use the survey result, the project decision was made: Add FFWs!!!
> and keep surveying!!!
>
> How's the survey information being used in your projects? How
> accurate they may be? Do you eliminate any FFWs because of using
> survey results?
>
> Thanks for any reply.
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[Non-text portions of this message have been removed] Received on Mon Nov 01 05:50:00 2004
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