Issues with inserting rcp file in Revit

[NDM_USER]

My friend asked me to confirm if the  positioning of the recap file imported to a  Revit file is corect or not.Tough task considering that I can't just snap the ID of a known point from the cloud in Revit and reveal the northing and easting.

So... I have started from my design file in Revit.

1. I have confirmed the shared coordinates of the file by specifiying coordinates at a point of intersection of two gridlines.
2. Check the coordinates from point cloud to match the same UTM from design Revit file.
3. Index and import rcp to Revit- positioning by shared coordinates
4. Draw a feature (circle) using the point cloud as background
5. I have exported the view to CAD ( dwg) using the same units ( meters) and shared coordinate system
6. Import rcp to AutoCAD file -exported from Revit - import using no insertion point 

Conclusion : The same feature (circle) in revit and  autocad had the same coordinate system , however the same recap file was located in two different locations in CAD and Revit. The location from AutoCAD was correct, the location from Revit was 2 feet apart. 

Let me know if you have any suggestions how to fix this bug!!!

Dorin Nita

[RDAOU]

As a quick suggestion (No access to Revit at the moment)...

• When you say that you verified that coordinates from point cloud match the UTM from Revit file and confirmed shared coordinates of the file...does this include Alignment of coordinate systems between AutoCad and Revit (orientation to WCS, North "up")? No point of setting something up in either Revit or ACAD if it wont align correctly in both. And I know its silly but double check UCS is set to WCS and Plan to WCS and remove any other named UCS which are not required before importing. Additionally, when linking/importing some files with considerably large survey data/coordinates, Revit sometimes encounters file extents that are quite large; mostly when the extents of the file violate the current 20 mile tolerance Revit has which subsequently might/can affect the way Revit abbreviate UTM coordinates (sometimes this behavior is unpredictable and could occur even when not close to the 20 mile extent tolerance). Hence in the absense of proper alignement between Revit and AutoCAD (which doesn't have this extent tolerence) it could cause such errors.

• Not sure if your Revit and AutoCAD were aligned before you carried out the import; I would sugest that you try using Atuo - Center to Center positioning option instead of Shared or O2O (Personal Preference even when/if the point cloud is sampled with respect to the known point/direction in your model or on your site.). I would use Shared Coordinates and/or O2O only if I know before hand that both Revit and AutoCAD coordinate systems are aligned

• Another problem would be if your linked file will be positioned further than 1.6 km (2miles) from 0,0. the shared coordinates process will not work out. ie: the Shared Coordinates origin should be less than 1.5 miles from the Project Coordinates origin for import by Shared Coordinates to work seamlessly. Revit's math do not like very large coordinate numbers. When numbers get large, the differences (when exporting/importing b/w to different programs) may become large enough to effect the results of display and operations (an error is an error regadless of how slight or big it may be 2" or 2' or 2 miles). ie: best keep Revit project/model near Revit's origin. (near means within 1 mile/1.6km) Revit's origin is near the center of the space made by the elevation symbols in the default template.

[NDM_USER]

The project is 500 m long , the north is ... the true north...

Here's the response from Autodesk:

"Hopefully development will address this in the near future"!!!

I'd like to thank Alan Quinn for providing me with the work-a-round which is.... convert point cloud to rcs.It works ......Almost great.Instead of 2 feet now I have only 2-3 inches discrepancy.

Until "the  near future"  I'd like to thank everyone and stay away from geolocating point cloud using Revit.

Thanks

Dorin