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Thread: Revit survey point when publishing coordinates ?

  1. #1
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    Revit survey point when publishing coordinates ?

    Hi,

    I have been using Revit for about a year and recently read up on Revit's survey point, project base point and origin, not because I have a specific problem/task that I am trying to get around, I just like to fully understand the tools I am using. I have done lots of internet research and generally understand the principles of Revit's coordinate systems but am coming across something specific that I am not understanding but can't seem to find it tackled specifically in other articles or posts.

    Using Revit2016, I am setting up a site model which I plan to link in my building model....

    My site model is set up with coordinates acquired from site survey autocad dwg and everything checks out ok when I place a spot coordinate etc.

    Next, I link my building model auto center to center and manually move it to where I want it on the site.

    Next I publish coordinates from the site model to the building model and save.

    I then test it by removing the linked building model and re-link using shared coordinates and it works.

    I also then test again by re-linking using auto origin to origin and again it works.

    Next, in the interests of me being confident about things having being done properly and trying to understand what Revit is and isn't doing, I open the linked building model and check the coordinates of the survey point to check they match the site model but they don't.


    Does this sound as experienced Revit users would expect ? I expected the survey point coordinates to match between the two linked models.

    Or is it that when revit publishes coordinates from a site model to a linked building model that the survey point is not included ?


    Thanks

  2. #2
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    Quote Originally Posted by DeanB72
    Does this sound as experienced Revit users would expect? I expected the survey point coordinates to match between the two linked models.
    Yes, that's normal.

    When you open the Building model the Survey Point (SP) is marking its own origin, which is 0,0,0. When you examine the Project Base Point (PBP) you'll find coordinate values that indicate how far away it is from the SP. If you unclip the SP you can move it closer to the building and you'll see the coordinate values change to show how far the icon is moving away from its origin .

    The attached image shows the initial position, in the Building file, of the PBP and SP after using Publish Coordinates to pass the Shared Coordinate system information from the Site file to the Building.

    When you use Acquire Coordinates Revit moves the SP (when it is Pinned) to mark the location of the World Coordinate System origin (WCS assuming a DWG site source). When you use Publish Coordinates on the Building file it does the same thing but the SP is marking the WCS origin, which is 0,0,0 in the DWG...and for the SP of the building model too.

    Quote Originally Posted by DeanB72
    I then test it by removing the linked building model and re-link using shared coordinates and it works.
    I hear and read that a lot. Don't do that on a real project since it will open the door to messing up the work you've just done. Link the building model, re-position it and Publish Coordinates. Leave it alone unless design changes require it to be moved again. A better test is to link the Site model into the Building model using By Shared Coordinates. That doesn't change anything you've done and you'll see they line up properly.

    The second image shows a building that has been altered via Publish Coordinates. The orientation is assigned to Project North but the spot coordinates are reporting SP related coordinate values; except for the one next to the PBP which I changed to refer to the PBP instead.
    Attached Thumbnails Attached Thumbnails Revit survey point when publishing coordinates ?-pbp-sp.jpg   Revit survey point when publishing coordinates ?-pbp-sp02.jpg  
    Last edited by Steve_Stafford; September 27th, 2016 at 01:07 PM.

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    Quote Originally Posted by Steve_Stafford View Post
    Yes, that's normal.

    When you open the Building model the Survey Point (SP) is marking its own origin, which is 0,0,0. When you examine the Project Base Point (PBP) you'll find coordinate values that indicate how far away it is from the SP. If you unclip the SP you can move it closer to the building and you'll see the coordinate values change to show how far the icon is moving away from its origin .
    Thanks for the reply Steve but one of us is misunderstanding something (admittedly there's a good chance it's me) but...

    When I open the building model (after coordinates have been published to it), the survey point is not at 0,0,0 according to the coordinates nor is it at the original project base point (which is also the original 0,0,0. I believe) and nor is it at the 0,0,0 of the linked survey dwg. The survey point marker is located at the same point that it was before coordinates were published to it (an arbitrary point).
    Which is what confused me in the first place..... Why is the building model survey point located at the same arbitrary point that it was before the shared coordinates were published to it ? Or is it simply that the building model survey point is of no relevance to the site model ?

  4. #4
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    When you link a DWG file into your site model and use Acquire Coordinates the SP should jump (SP is clipped) to mark the same spot that is the WCS origin in the DWG.

    When you link the building RVT into site and then use Publish Coordinates nothing visible happens to the model. When you save your site project you'll be asked how you want to deal with the change you made to the Building model (altered the linked file with the Publish Coordinates tool). If you choose anything other than Save (top choice) then you're not retaining the changes you intend to. That might account for the difference.

    The following 4 blog posts of mine might help?

    Survey Point Post 1
    Survey Point Post 2
    Survey Point Post 3
    Survey Point Post 4
    Last edited by Steve_Stafford; September 27th, 2016 at 02:31 PM.
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    OK, I have gone through the acquire coordinates process again this time making sure the site model survey point is clipped which now results in the site model survey point disappearing off screen to what would be the 0,0,0 of the survey dwg. But I'm still getting the same result when I publish coordinates to the building model.....when I open the building model, the survey point within that model is still where it initially was. Would you have expected this to have moved somewhere ?

    Thanks

  6. #6
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    Quote Originally Posted by DeanB72
    ...I'm still getting the same result when I publish coordinates to the building model.....when I open the building model, the survey point within that model is still where it initially was. Would you have expected this to have moved somewhere?...
    That will depend on how the template you are using is configured.

    If the SP in your building file is not clipped then it won't move when Publish Coordinates is used...it will just provide coordinate values relative to the offset from the Shared Coordinates origin location. Keep in mind that you have to Save the location when Publish Coordinates is used otherwise nothing will change in the building file.

    If the SP is clipped then it should be moving to mark (match) the origin of the Shared Coordinate system, from the site model.

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    Thanks Steve..... that's almost fixed it.....the template that I created had the survey point unclipped. So having now got it behaving the way I expected it to, my instinct is now telling me that I don't want the survey point a long way from the building so I planned to move it to a point near the site that is part of the topographic survey (a survey point with a known grid reference coordinate) but are there any reasons to do this or not do this ?

  8. #8
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    Quote Originally Posted by DeanB72
    ...I don't want the survey point a long way from the building so I planned to move it to a point near the site that is part of the topographic survey (a survey point with a known grid reference coordinate) but are there any reasons to ... not do this?...
    No, I do it all the time. I usually don't clip the SP in the first place because I plan to move it to a known location relative to the building/survey info. It's more meaningful to me and the project if the SP reports relevant information.

    Revit moves it to mark the WCS origin when it is clipped because it is meant to make it more obvious that it is (a) just different and (b) marking the alternate coordinate system instead.

    You can also choose to turn off the SP and PBP and use Spot Coordinate annotation to mark locations instead. If the Spot Coordinate annotation type is assigned to Survey Point then you'll get survey related coordinate values for whatever you apply the annotation to.
    Last edited by Steve_Stafford; September 27th, 2016 at 03:44 PM.

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    So if you regularly move the survey point (presumably in the site model ?) then does it never cause problems further down the line because the site model survey point is in a different location to the building model survey point ? It feels wrong to have each model having a survey point that is different.

  10. #10
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    Quote Originally Posted by DeanB72
    ...So if you regularly move the survey point...
    No, I don't regularly move the SP. I move it once if I move it at all. Then I never touch it again (per project). ALWAYS un-clipped...not clipped. Moving the SP while not clipped causes Revit to regard it as annotation, it does not alter the shared coordinate system. If you move the building's SP while not clipped then, since it's just annotation, it can mark whatever location is meaningful. That doesn't mean you should develop a habit of moving it around anytime for any old reason. If you need to annotate coordinates use the Spot Coordinate (and/or Spot Elevation) tool.

    That written, that also means moving the SP while clipped is changing the Shared Coordinate system...it moves the origin of that system. You'll screw up the Acquired Coordinates.

    Fwiw, if you did not use Acquire Coordinates at all you could just move the SP, while clipped, to a specific location relative to the linked DWG survey and define where the origin is manually. The only difference between doing that manually and using Acquire Coordinates is that Revit makes an internal note that it has Acquired Coordinates from the DWG. Trying to do so again later will generate a message that it has already been done. Acquire Coordinates just makes that process easier, note I didn't write simpler.

    Quote Originally Posted by DeanB72
    ...It feels wrong to have each model having a survey point that is different...
    Technically they are not different...if they remain clipped they will be in the same location. It is just when they are unclipped that they can be in a different location from file to file. The origin (shared coordinate system) is unchanged, just the triangle annotation is in a different location.

    My recommendation:

    • Set up the site master file
    • Link building(s)
    • Publish coordinates
    • Turn off the SP and PBP in all files
    • Leave them alone and tell others to stay away from them
    • Use Spot Coordinate annotation to document specific locations relative to the site survey
    Last edited by Steve_Stafford; September 27th, 2016 at 06:24 PM.
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