Error in Dynamo script because survey point has been moved

[iainsavage]

I'm not sure if this is a Revit query or a Dynamo query but here goes.

I have a project set up by someone else in which:

• The internal origin is at the existing floor level
• The project base point is at the proposed floor level
• The survey point has been moved (unpinned?) to sea level

I've set up a test project to simulate the error:

I'm using a Dynamo script provided by Aussie Bim Guru (slightly modified due to version differences) to insert spheres at each clash location taken from a Navisworks report.

The script includes a translation section to translate Dynamo coordinates to Revit coordinates.

But the Z coordinate of the spheres comes in wrong and after a bit of trial and error I figured out that its because the survey point is lower than the internal origin point and the Z offset is what is causing the error.

My problem is that the internal origin reports its Z value as zero and the survey point also reports its elevation as zero, even although its at a different Z value than the internal origin. So if I try to use a formula to work out the difference in Z values it just results in zero difference.

The only way that I've so far been able to correct the error is by manually inputting a number to the Z value of the Point.ByCartesianCoordinates node.

So my questions are:-

1. Why does this Z offset error occur in the first place since I'm not using the survey point data in the GetProjectLocations node and
2. How can I correct this using a formula rather than having to manually derermine the offset value and input it manually.

[ToanDN · Accepted solution]

The survey point needs to move while clipped. Moving it unclipped means not moving it at all, only changing the symbol location.

[iainsavage]

I didn't have control over this.

The Architect set up the various origin points and I think the logic to moving the survey point (presumably unpinned) was so that levels could show height above sea level if the level type references survey point or the nominal site levels (if set to reference project base point) without physically moving the model.

Moving the survey point whilst pinned changes the elevations of the levels relative to sea-level.

I suppose I'll just need to stick with inputting a Z offset manually.

[ToanDN]

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@iainsavage wrote:

I didn't have control over this.

The Architect set up the various origin points and I think the logic to moving the survey point (presumably unpinned) was so that levels could show height above sea level if the level type references survey point or the nominal site levels (if set to reference project base point) without physically moving the model.

Moving the survey point whilst pinned changes the elevations of the levels relative to sea-level.

I suppose I'll just need to stick with inputting a Z offset manually.

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Nope.  If they wanted the Levels to show actual elevations relative to the Sea Level then they must have moved the SP clipped while having the Levels use SP for Elevation base. 

Moving SP unclipped is purely cosmetic, it neither changes the actual SP location, nor the relationship between SP and PBP.  The reason the function exists is to bring the symbol closer to PBP / the model when its actually too far away.

[iainsavage]

So if I move the SP upwards unclipped, then clip it and move it back down the levels should still display the correct elevations, positions of links won’t be disrupted and my Dynamo formula should work? Am I understanding this correctly? (8 years and I still get confused by the various origins and their effects on models).

[iainsavage]

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@ToanDN  schrieb:

The survey point needs to move while clipped. Moving it unclipped means not moving it at all, only changing the symbol location.

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I've accepted this is the solution but it can't be the full story because the relocated survey point shows elevation as zero, the internal origin elevation is zero, yet Dynamo somehow recognises that there is a difference in elevation between the origin and the survey point symbol.

Rather than play about with the settings of my model I have, for this project, left the survey point where it was and have just used the manual input method to correct the Z offset.

Thanks for your help.