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    Problem with rotating true north

    I have received a re-survey of an existing site survey (first one was to local grid, new one is to OS grid). I have the same stations marked on both surveys so have lots of common points. It seemed easier to mark 3 of the common points, survey stations, in my Revit file, remove the old survey, and then CAD link in the new survey.

    I can then position the new survey to my marked up station points, rotate to suit, re-establish the new coord's and finally, rotate my true north to position.

    Problem is, this is a big site. When I check out the rotation of where true north actually is, its around 9 decimal places off, ie "6.449136158". So, I set my rotation to the west, at this very large rotation number, and Revit then of course converts this to Degrees, minutes and sec's, and rotates it to suit. All looks good on the face of it. Problem is, because of the size of the site, this doesnt cut it for accuracy and my coord's are now off by around 5 - 20mm. I know this isnt the end of the world, but I should be able to set this virtually 100% accurate. All my survey stations line up as they should, its just the true north rotation that is causing me grief.

    Is there something I am not doing here, or am doing incorrectly..?

    Cheers
    I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it

    #2
    Well.. just to update my situation..

    I managed to sort this out, via the "rotate true north" command, and also not trying to rotate it by a very small amout. I needed the rotation to be around .000030508. So, I rotated it one way 90.000030508, and then back the otherway 90.. Seemed to do the trick...
    I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it

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      #3
      We have been having similar issues on a large job, and had to do exactly that: Rotate it an arbitrary large amount, then rotate it back.

      The bad news? Using "Rotate True North" on a model that has Shared Coordinates set up already, completely tweaks the file for Units and Translation in Navisworks. Havent had a chance to file a Support Request about it. =(
      Aaron "selfish AND petulant" Maller |P A R A L L A X T E A M | Practice Technology Implementation
      @Web | @Twitter | @LinkedIn | @Email

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        #4
        Just a quick reminder of Iru69´s fine tutorial on the subject
        Klaus Munkholm
        "Do. Or do not. There is no try."

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          #5
          Originally posted by Alfienoakes View Post
          Well.. just to update my situation..

          I managed to sort this out, via the "rotate true north" command, and also not trying to rotate it by a very small amout. I needed the rotation to be around .000030508. So, I rotated it one way 90.000030508, and then back the otherway 90.. Seemed to do the trick...
          Seems quite logical behavorial to me... You can't move by 0.000030508mm (or inch) either.
          Martijn de Riet
          Professional Revit Consultant | Revit API Developer
          MdR Advies
          Planta1 Revit Online Consulting

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            #6
            I have noticed the same problem when using the move tool (as opposed to rotate) on any number of elements when the view is zoomed right in. The move tool can also be inaccurate over distances as large as a few mm, and the same "move it away, then move it back" method must be employed.
            I think the issue is caused by how Revit calculates how far to "move" or "rotate" elements depending on level of zoom and scale of the view.
            There are no stupid questions, only stupid people

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              #7
              Its also giving me the "geometry too large... 20 mile extents" problem as well.. Its possible that I have some CAD links and Revit links in there that are on the old local OS grid, and the new National OS grid is is too far away now..? Thinking out loud as Im typing here.. I have checked all the geometry in my new files and there all ok.. no rogue bits floating around.. Must be the difference between the old positioned links, and the now new set up co-ord system.

              Will take a few out and try this..

              Aaron, thats interesting.. We arent into any Navisworks workflows yet, but I may be in the near future on future projects. We're hopeful that this wount of course happen regularly as it was really a mistkae by the survey company some years ago.. but you never know....
              I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it

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