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    Shared Positioning

    Ladies & Gentlemen,

    Any insight you could offer based on the following questions and comments would be appreciated. Thanks!

    When it comes to having multiple models linked into a site model and where coordinates are being shared. Is it true that the survey point should be at 0,0 representing a benchmark and that the project basepoints of the linked models should display coordinates relative to the survey point in order to locate those models on site?

    In the above scenario would the link user start their model from the OOTB project base point location such that a logical point sits on the project base point at 0,0?

    When they acquire coordinates or have coordinates published from the site model would the project base point read relative to the shared survey point from then on?

    What happens if the links project base point needs to move within that model at some point?

    If a set of gridlines is known and an intersection of two gridlines is to occur at 0,0 in each model is there a need for shared positioning?

    When would you and when wouldn't you use shared positioning?

    #2
    Originally posted by HelmetFire View Post
    Ladies & Gentlemen,

    Any insight you could offer based on the following questions and comments would be appreciated. Thanks!

    When it comes to having multiple models linked into a site model and where coordinates are being shared. Is it true that the survey point should be at 0,0 representing a benchmark and that the project basepoints of the linked models should display coordinates relative to the survey point in order to locate those models on site?
    First, which "0,0" are you asking if the Survey POint should be at? Project Base 0,0, Survey 0,0, or Relative 0,0?

    Honestly, it doesnt matter where the Survey Point is, and i dont think ive ever cared one way or another. Mine is always at the 0,0,0 of the Shared Site Coordinate System, but thats only because thats where it goes when you set up the coordinates, and i dont care to move it anywhere else.

    In the above scenario would the link user start their model from the OOTB project base point location such that a logical point sits on the project base point at 0,0?
    As far as im concerned, they can do whatever the heck they want with Project base. I want Relative Origin to be in the same place, so CAD files dont become a catastrophe when exported (later), but even that is a convenience. The way Shared Sites work, every discipline can pretty much start their model wherever they want, and the Shared Coordinates align them all later.
    When they acquire coordinates or have coordinates published from the site model would the project base point read relative to the shared survey point from then on?
    Of course not. Project Base is always going to read off Project Base. If you want to read Relative to the Shared Site, you use Shared Coordinates.

    What happens if the links project base point needs to move within that model at some point?
    Then move it. Who cares?

    If a set of gridlines is known and an intersection of two gridlines is to occur at 0,0 in each model is there a need for shared positioning?
    Yes. Because in 3d space, simply knowing there are grids out there at "that point" and lining them up, doesnt help if everyone is exporting things in a silo.

    When would you and when wouldn't you use shared positioning?
    I use it on every project. Some people say they dont, but ive never seen a reason i (personally) thought was compelling. I use Shared Sites on every job.
    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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      #3
      My general advice:
      • Revit to Revit building files should link: Auto-Origin to Origin (this way they line up automatically)
      • Survey file(s) link to Revit: Auto - Center to Center
      • Don't move the Project Base Point while it is clipped (it's possible to be moved unclipped for local (this file only) coordinate purposes, spot coordinate annotation)
      • Survey Point represents survey file World Coordinate System origin (using Acquire Coordinates shifts the survey point to this location)
      • Optional: Move survey point unclipped after using Acquire Coordinates so it is closer to the site and at a known benchmark

      Subtlety, Project Base Point displays coordinate values relative to the Shared Site (Survey Coordinate system). I think that's confusing because it is suggestive of a connection or relationship to the survey coordinate system. There isn't...they are two separate planes. The only one that actually moves is the survey coordinate system. Watch my little video explanation of the two systems if you like.

      If you have control (can save changes) of all the project Revit models then Publishing Coordinates can be useful to pass along the survey coordinate information obtained from linking and Acquiring Coordinates of the survey. When you don't the other discipline's models should use Acquire Coordinates from your (assuming you are the architect) model(s). Alternatively everyone can use Specify Coordinates at Point to change their own file's survey coordinate system.
      Last edited by Steve_Stafford; December 20, 2017, 09:53 PM.

      Comment


        #4
        Steve,

        Thanks for your eloquent reply and the links. I’ve been reading your blog posts on this and they are helping.

        If your site information is a .csv file that is used to create a toposurface, can this element be created in the master site file in it’s real world position or would one just create it Center to Center and specify coordinates at a point? This particular .csv has values 6500 km N/S and 580 km E/W so I worry the offset from it’s origin and the topo could be too great. Thanks.

        Comment


          #5
          Once the toposurface is created move it so its extent is centered on the Project Base Point. Use Specify Coordinates at Point (SCaP) to provide the correct survey coordinate system origin relationship. That might be tricky (identify a Point) if your only source is the .csv file. If you add a single point coordinate for 0,0,0 to your .CSV then the surface will provide something obvious to mark it. Just edit and delete the point, that is placed at that location, after using SCaP.

          Comment


            #6
            Originally posted by Steve_Stafford View Post
            If you have control (can save changes) of all the project Revit models then Publishing Coordinates can be useful to pass along the survey coordinate information obtained from linking and Acquiring Coordinates of the survey. When you don't the other discipline's models should use Acquire Coordinates from your (assuming you are the architect) model(s). Alternatively everyone can use Specify Coordinates at Point to change their own file's survey coordinate system.
            Steve,

            Please confirm that if others have acquired coordinates from me and we have since moved our project to a new location relative to the site by moving the PBP while clipped that the others should now SCaP before receiving our updated model. Thanks.

            Comment


              #7
              Originally posted by HelmetFire
              ...Please confirm that if others have acquired coordinates from me and we have since moved our project to a new location relative to the site by moving the PBP while clipped that the others should now SCaP before receiving our updated model...
              Short answer, no.

              When your model is reloaded by the other team, in their hosting model, they should find your building is in a different location. That means, assume HVAC for a moment, their ducts, air terminals and equipment will all be in the wrong location.

              As such, you need to tell them how you moved it; X,Y,Z, and rotation. Using SCaP won't shift their model to line up with yours (see below).

              They should not move your linked file. The Shared Coordinate System is in sync already. Your building moved relative to theirs because you redefined the relationship between your building and its Survey Coordinate System.

              Alternative: If they disable shared coordinates for your linked model by using the Option: Do not share site of Selected Instance (Instance Property of link called Shared Site) and then move your model to line up properly...then they can use SCaP. Your files won't be sharing coordinates any longer but it will be in the correct location. Sounds like a win, but it won't fix alignment issues between your own model and theirs when you link it into your model or reload the link if it already is. You'd have to do the same thing with their linked file. Either way you're fixing something.

              Comment


                #8
                Steve,

                I do want to preserve the sharing of coordinates. The following seems to work via test, see any issues with it?

                When receiving a new version of my model which includes a building relocation they...

                unload my model (to avoid that frustrating moment when things are misaligned and errors and warnings come up)
                move the PBP while clipped the same way I did
                save the new version of my model over the previous
                reload my model

                Thanks for all your help on this.

                Comment


                  #9
                  I don't know that I'd unload the link. I'd want to see it move into alignment, even use some aspect of it to help me move it (PBP). There shouldn't be a positioning related warning. There could be tag or dimension related warnings. It all depends how far along their model, and the project, is. Also that kind of warning will happen before they get to fixing the positioning since your model will open in the new location while their work is where it used to be.
                  Last edited by Steve_Stafford; January 19, 2018, 10:05 PM.

                  Comment


                    #10
                    Coordinates and building positioning has confused me for years. This (long and very detailed) procedure by Brian Renehan has clarified my thinking. It also deals with collaboration and data exchange issues. I am trialing it on a couple of projects now: I like it so far, with a couple of tweaks.

                    https://www.revitforum.org/tutorials...blishment.html
                    BIMFix Blog: Framework

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