Forums >> Revit Building >> Technical Support >> Shocking Survey Data, nothing drawn to a UCS! slightly off axis errors imenent!!

JRPcad

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Joined: Thu, Jul 1, 2010
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Okay guys, Ive been asked to produce an as built model of a rather large building which seems to have been built off a fairly tidy grid. However, as my subject suggests the Surveying company have neglected to draw this to a UCS meaning that not one of the columns/steels/walls etc. are parrallel.

I've not properly started this project yet but am pretty worried that when the architect eventually gets the finished result he's going to kick up a big fuss about things not joining correctly and not being able to dimension anything.

I can get Revit to correct lines slightly off axis when I import it but not sure exactly what it's going to move and ideally my model will need to match the survey in some way.

I'm really stuck with what to do, is there an automatic fix that Revit can correct the many thousand errors I'm going to encounter??? At the minute I'm drawing leaving everything to true north and haven't picked a project north (mainly because I don't know which "horizontal" line to pick) so I'm dodging the errors.

Any help or advice will be much appreciated

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For Architectural Services visit www.jrpcad.co.uk

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WWHub

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Joined: Tue, May 16, 2006
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I would think that the initial design was to a proper grid and that the survey is too exact to fit it.  I would "drive" my own grid through the project using the assumptions that it is parallel and a regular dimension. 

If that grid approximates the centers of the existing columns within the structural construction tollerances, then your right on.

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JRPcad

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I think you're spot on Hub (as always )

It's probably not exact though it's more than likely what their equipment told them and they used no logic. I think the way to go is to build my own grid as you say and align everything to it, better that than created thousands of slightly off axis errors, I think the architects will appreciate a tidy version of the shoddy survey they have, hopefully we don't get any come backs about the model not matching the survey exactly.

Cheers

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JRPcad

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mmm just ran a gridline from one end column centre to the other end column centre and some of the columns in between are 30-40mm off centre which is quite a bit more than the acceptable 25mm tolerance, I guess i'll have to do this project completely off a grid

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WWHub

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If you moved your column line to one side or then other- then how do they all work?

I would still use the grid.  Long before computers, we often placed columns off the grid and dimensioned them accordingly.  A-1 Col was still A-1 column even if it was 6" off the grid.

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