Sharing Coords Issue

[Anonymous]

Hello Revit Community,

I have an issue that I would like share with you and maybe anyone can explain us why this happens.

We have a set of drawings in the correct coords and we would like to link it by sharing coords.

I will explain you the process I follow:

1.Open a new project.

2.Link the first CAD, CENTER TO CENTER.

3.Move the CAD and ROTATE it to the location and rotation according to our PROJECT NORHT.

4.ACQUIRE coords from this CAD, and PIN it.(The shared site in the properties of the dwg change from Not shared to Default Position)

5.Go to my other levels and link by share coords the rest of the set.

THE QUESTION IS WHY WHEN I SAVE THE PROJECT I NEED TO DISABLE SHARED POSITIONING (Retains the current placement of the link and clear the Shared Position parameter), OF ALL THE DWGs EXCEPT THE FIRST ONE IN ORDER TO NOT AFFECT THE COORDS OF THE DWGs??????

MANY THANKS,

[Alaaeldin_Alsahli]

Please follow senario 2 in the link below and let me know if you still have this message again

http://revitclinic.typepad.com/my_weblog/2009/12/project-location-dialog-disable-shared-positioning....

[Anonymous]

Thanks Alaaendin,
But in that post there is not explanation why I need to disable sharing coords.
That is the process we follow, as you can read in my post, however I'd like to know why Revit interprate that the link need to be change to new coords if in reality those remain the same.

[Alaaeldin_Alsahli]

Which Revit version are you using?

[Anonymous]

2014 & 2015

[Alaaeldin_Alsahli]

I will double check with the development team and see why.

Does this Dialog go away after the first time?

Bottom line - if you acquire coordinates they will need to save changes back to the link

That’s the way it should be at least

I think is just a confirmation but the dialog should not reappear but as i said i will double check why

[SteveKStafford]

I've encountered this message a few times too. Ordinarily I don't though. The process should not need to save a UCS back to the source CAD file but in some cases Revit seems to think it must.

In my opinion (and consistent with all past releases of Revit) Acquire Coordinates should never need to save a UCS back to the CAD file used to acquire coordinates from. It is only a Pull transaction, pulling data from the survey file. Only if Publish Coordinates is used on that file should a UCS need to be created for the file. It seems to me that it is possible that something was changed in the underlying code in the last round of improvements to DWG export/import capabilities.

I also suspect that this is a symptom of slight inaccuracies between the source file and the Revit file. For example, the rotation angle used to match coordinates or the coordinates themselves may be too precise (many decimal places) and the value(s) get truncated. If this happens then Revit thinks there is a very subtle discrepancy between files and believes it must provide a UCS in the source CAD file so exported data will be able to align with it when it is imported into the file.

Since I've seen it happen with some files and not others I'd be suspicious that the angle required to align the survey and Revit model is too precise. For example, a rotation of 46.000300050004 degrees is very precise. If 46.000000 degrees is what ends up being used during your alignment attempt Revit may see that as different enough to prompt the warning message.

I wrote THIS POST on my blog when I encountered this the last time but it was related to importing using the By Shared Coordinates option, before any such relationship really existed. It was just to force Revit to import the file using the WCS instead of using center to center.

[Alaaeldin_Alsahli]

I guess there is an IF condition that is detecting any file that is not from its original position.

So when you insert by shared coordinates, it detects righ away that this link is been moved from its original position.

we don't see it but in the backround process I guess it inserts it first to its original position and it move it to the shared one. It can't just position it directly to the shared one

I will check if it is possible to fix this for future version.

[Alaaeldin_Alsahli · Accepted solution]

I got an answer from the development team and it is considered as design here the reason

In Revit backround process when doing the save, all linked DWG files will be checked if they are having a new change or not.

By acquiring coords from the first linked DWG, its coords will be applied to the current project, Where for the rest of the dwg's, thier coords did change so this is why this dialog only shows up for the DWG which has new changes.

[Anonymous · Accepted solution]

Alright,

It is quite confusing anyway.

Many thanks.

[SteveKStafford]

That means they are assuming the files we are linking don't already share an agreed upon file alignment strategy between the people that created them. If I understand their logic, it means that using Positioning: Auto-By Shared Coordinates when we link a file triggers a response in Revit that it needs to create a UCS (User Coordinate System) to permit AutoCAD users to align these files if they are combined in AutoCAD at some point.

Revit can't know if these files have an agreed upon relationship to the WCS origin because in AutoCAD that's a subjective user based agreement, not something captured in code. In other words we agree as users to draw things relative to 0,0,0 in a specific way so our files will line up when we use them as an external reference.

For multiple survey file relationships that's not most likley not necessary and just creates confusion. I can see how it might be useful if we are mixing a variety of trade files that might not have discussed how their work relates to the WCS origin. However that seems an outlier condition to me, especially if Revit happens to be the primary platform in use.

The shorter answer is: Choose Disable Shared Positioning (for the file involved, not the one that was used to Acquire Coordinates originally). This way Revit isn't concerned about creating and saving a UCS in the file that's been linked.