1. Revit coordinate systems for the rest of us
When I proposed this presentation I hoped that while researching there would be a Eureka moment like so many times before with Revit. Uncovered some truths, but no Eureka.
The more I looked the more excuses my mind made up for me – just in case!
I do however now have some clarity of the basics of how the system works.
There are some people here with much more experience – please shout if Incorrect.
How many coordinate systems are there in any Revit project?
The answer start with “At least…” Quick Show of hands 1, 2, 3

2. Usual suspects
It actually looks a lot more like this, I found 18 different places where the systems comes up in
Dialog Boxes
Error messages
On screen etc.
Deeply interwoven into the software as you would expect.
There are hurdles along the way

3. 4 degrees of freedom Pseudoazimuthal projection Local scale factor
No fancy geometric trickery in Revit.
All straight forward translations and one rotation around the Z.
Relativity however is important as the three systems can be translated relative to each other to produce a number of permutations.
We are going to examine the three systems and the associated two points which are separate entities.
Geographic North
GIS
Curvature of the earth
Transverse Mercator

4. The Internal Coordinate System
AKA The fixed origin. The most important coordinate system is invisible!
But it is visible as it is the model geometry!
All elements are stored relative to this Internal Coordinate System in the database – even views.
It is in inches and feet.
Good news: There is only one!

5. The Project Coordinate System
This one is a well named Point / System. Many of these are possible.
“Angle to True North” is a complete misnomer!
It indicates anti-clockwise rotation of the current shared system relative to the project system.
It should belong to the Shared Coordinate System! (Next slide)
Arrows indicates project N, E and Z directions.
N/S E/W and Elev indicate the distance of the PBP from the current shared system 0,0,0.
The Green arrow (N) Indicates the direction of UP in views oriented “Project North”.
The paperclip ??????????????
The clip clips the Project Coordinate System to the Internal coordinate system.
Clipped:
Entering a rotation angle will rotate the shared system relative the project system about the PBP.
In reality the Project Coordinate System cannot be rotated (fixed to internal system).
The screen will update if set to True North – but will rotate around the true origin!
Entering numbers or moving / dragging the point moves the current Shared Coordinate System origin.
But will move elements on screen to create the illusion of moving everything relative to the Shared origin.
This is the same as relocate project.
Inverse of moving the clipped Survey Point ie. The Shared Coordinate System!
Unclipped:
Moves the Project Base Point relative to the True Origin.
Shared coordinates do not change – this tells us that only the Project Coordinate System has moved.
Rotating the unclipped PBP is the same as the rotating the clipped one ie. True and Project cannot be rotated.
Right click – “Move to Startup Location” can return it to the true origin.

6. The Shared Coordinate System

7. The Project Coordinate System
This one is a well named Point / System. Many of these are possible.
“Angle to True North” is a complete misnomer!
It indicates anti-clockwise rotation of the current shared system relative to the project system.
It should belong to the Shared Coordinate System! (Next slide)
Arrows indicates project N, E and Z directions.
N/S E/W and Elev indicate the distance of the PBP from the current shared system 0,0,0.
The Green arrow (N) Indicates the direction of UP in views oriented “Project North”.
The paperclip ??????????????
The clip clips the Project Coordinate System to the Internal coordinate system.
Clipped:
Entering a rotation angle will rotate the shared system relative the project system about the PBP.
In reality the Project Coordinate System cannot be rotated (fixed to internal system).
The screen will update if set to True North – but will rotate around the true origin!
Entering numbers or moving / dragging the point moves the current Shared Coordinate System origin.
But will move elements on screen to create the illusion of moving everything relative to the Shared origin.
This is the same as relocate project.
Inverse of moving the clipped Survey Point ie. The Shared Coordinate System!
Unclipped:
Moves the Project Base Point relative to the True Origin.
Shared coordinates do not change – this tells us that only the Project Coordinate System has moved.
Rotating the unclipped PBP is the same as the rotating the clipped one ie. True and Project cannot be rotated.
Right click – “Move to Startup Location” can return it to the true origin.

8. The Shared Coordinate System
Default is: Internal ????
This should be called “Undefined”
Recommend you to rename them as soon as you establish them.

9. The Shared Coordinate System
Survey Point is a point on the current Shared Coordinate System – as named.
The numbers indicate the location of the point relative to the current Shared System.
Grey means clipped.
It does NOT indicate it’s own rotation relative to the project system despite sites defined in Location / Sites!
Arrows indicates Shared N, E and Z directions.
The paperclip ??????????????
Clipped is to the Shared coordinate system.
Clipped:
Inverse of moving the clipped Project Base Point.
Rotation should be available here!
Dragging the point moves the current Shared Coordinate System origin only.
This is the same as relocate project but in the opposite direction.
Unclipped:
(floating) point is there to find a point at a known coordinate.
Unclip and enter zeroes to return it to the shared system origin
Next up – spot dimensions

10. Spot Coordinates
Can be made to indicate Elevation

11. Spot Coordinates
Type parameters allows us to define Coordinate origin.

12. Spot Coordinates
Shared - Will report the X, Y (and Z) distance of a point from the origin of the current shared system.
Project - Will report the X, Y (and Z) distance of a point from the current location of the PBP.
Relative - Will report the X, Y (and Z) distance of a point from the fixed origin the Project Startup Point.

13. Spot Elevation Elevation only
Type parameters allows us to define Coordinate origin.

14. Spot Elevation Type parameters allows us to define Elevation origin.
This looks similar – but is completely different from Spot Coordinates.

15. Spot Elevation
Shared - Will report the Z distance of a point from the origin of the current shared system.
Project - Will report the Z distance of a point from the current location of the PBP.
Relative - Will report the Z distance of a point from a specified relative base level!!!

16. Spot Elevation

17. Spot coordinates – VS Spot elevations
Next up: Common operations.

18. Common Operations - Coordinates
Acquire coordinates : Aligns the current shared system to the import instance’s WCS.
Publish coordinates: Writes the current shared coordinates as a UCS to the link or as a shared coordinates to the Revit file.
Specify coordinates at a point: Moves the current shared coordinates to conform.
Report shared coordinates: Same as spot coordinate tool set to shared coordinate origin.

19. Common Operations - Position
Relocate Project: Moves the current shared system.
Rotate True North: Rotates the current shared system.
Mirror Project: Deep waters here – thoroughly check results afterwards.

20. Rotating Project North - It is not

21. Rotating Project North - It is not
You will notice how slow this operation is

22. Rotating Project North - It is not
Rotates all modelling, datum, view elements and all shared systems about the current location of the PBP! Detail elements are not rotated due to the fact that detail elements cannot be mass selected! The result is a physical overwrite of the coordinates stored in elements. Shared coordinates do not change for modelling elements but will do for detailing elements. Project coordinates also don’t change!
This will rotate objects out of view boundaries if not careful.
Do this early in the project!
If you have gone too far – use the scope boxes to orient views.

23. Tips Model close to the True Origin (20 mile radius)
Select a good Project North of your preference as you’d like most plans to appear on sheets.
The speed of the operation will give a clue as to what has occurred.
Everything is modelled (even detail items and views) to the internal system ie: moving either the SP or the PBP will not move detail elements relative to model elements or crop boundaries, views, datums etc.
Stay within the 20 mile radius with your models.