Project North Thrue North with shared coordinates

Here we go again… I have written about this subject in Revit before. I have written that I am quiet fed up with how Revit handles it and so I have said True North it is. No more rotating…

Ofcourse it’s not all black and white. Recently during a Revit Structure training the subject got to the table again. Ofcourse this question came after I had setup the project base point. Not surprisingly things didn’t go as planned.

In order to try and explaining it I went on to show the odd behaviour of rotating either project north or true north. It’s my conclusion that you don’t want to use these tools after you have setup the project base point. So far I have only been able to get it wright by using the wrong setting… True north is project north and vice versa. That’s no way of working so let’s try to get it right.

After a bit of testing it seems that if you do the project north before you link the first dwg things go right.
Original post:
In red are the steps extra for Project north True North

Steps: Autocad

  1. open the dwg from the site
  2. choose a easily recognizable point as a project basepoint
  3. use the ID command in autocad to find it’s xyz values
  4. create a symbol, I prefere a circle with a cross, and place that ontop of the choosen point
  5. move the symbol to the nearest round value (important because of rounding in Revit)
  6. This location is going to be the project base point
  7. copy the ID value of this point and paste it into notepath
(24 July 2014 because of new insights I suggest you don’t use Project North and True North at all!) USE a scopebox if you want to draw orthogonal!)

Steps: Autocad for getting true north setup properly
  1. Take or draw a line in Autocad that you want to be horizontal in Revit
  2. Dimension the angle of this line with a true horizontal line in Autocad
  3. Rotate the line, that is going to be horizontal in revit, to such an angle that it is rounded at the third digit behind the comma. (normally this should be fine enough)

Explanation: you migh have a line that is at an angle of 20.52045493°. This number will give trouble in Revit. You can’t use that number in Revit. It will round it down for you. I like to have controle over this therefore I do the rounding. I would rotate this line in Autocad to be at 20.520°. 

If that is not precise enough round it maximally at the 6th digit: 20.520455°. 
To give you an idea of the precision you are dealing with. If you draw a two lines that are both 1000 meters long and you rotate one of them to 20.520 and the other to 20.52045493° the ends of those lines are 7.9mm apart. If you would use 20.520455 the the ends would be 0.00000122mm apart. (For the metrically challenged people, an inch is 25.4 mm)

  1. Copy the rotation value of this line and paste it into notepath
  2. Save the drawing
Steps: notepath
  1. Be aware most coordinate system are in meters and Revit models tend to  be build in mm.
  2. This means you need to move the comma 3 spots to the right
Steps: Revit
  1. Open your level that has a Z value of zero
  2. Goto visibility and graphics
  3. Goto the site category, expand and turn on survey point and basepoint
  4. Select the project base point (the circle)
  5. Copy the X value from notepath into the E/W
  6. Copy the Y value from notepath into the N/S
  7. Copy the rotation value to the: ‘angle to true north’ value
Do not paste these values into your instance property window, you will get an error. If you paste them into the on screen thing it will accept those values.

Be aware you survey point will move away from your project base point. The project base point is still located on the Revit origin!

If you take a look at your survey point you should see that it’s values are all zero. Your autocad origin (0,0) will be lined up with your Revit survey point.

Steps: Revit
  1. Goto Insert –> link CAD
  2. Choose the dwg with the site information
  3. Set Import units to the meters (assuming it has been drawn in meters)
  4. Set positioning to by shared coordinates
  5. press okay and you will get the next message
This is actually good because this should import the dwg origin on top of your survey point. This should also have the effect that the project base point marker you created in Autocad lands ontop of your project base point set in Revit.

Steps: Revit
  1. Pin the dwg. (it seems to behave better when re opening the project.)
  2. Goto visibility and graphics and turn of the survey point this will enable you to use zoom extends again
  3. draw two model lines in this view on top of Autocad lines
  4. Save the revit file and make an export the nwc
  5. Make sure that within the Navisworks export settings you set export to shared coordinates (do not use project origin)
  6. Make sure that within the Navisworks export settings you set the units to feet… (yes really!!!)
Steps: Navisworks
  1. Attach the dwg (the one you linked earlier into Revit)
  2. Attach the nwc from Revit
  3. take a look at the lines you drew in Revit and whether they line up with the Autocad lines. If they do you are good to go!
  4. if you select the revit nwc file and right click it and go to units and transform you should get a dialog box with coordinates that are the same as the coordinates of the project base point in Navisworks. (nice to check) 
  5. If they don’t check the steps and all the file and unit settings and adjust them accordingly where needed. If you still have problems contact me.
Project North Thrue North with shared coordinates

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