Project Coordinates, Shared Coordinates, and the new Survey Point
At some point I figured I'd delve into this and finalize my own contribution as to what these tools do -- they are very useful indeed for dealing with the need to move Revit's Shared Coordinates (SC) and Project Coordinates (PC) origins around.
First of all, you have to have Reveal Hidden Elements toggled on, or enable the visibility of these icons under the Site Category. Once you do, you can see the two icons:- Project Base Boint icon -- a circle with an X thru it
- Survey Point icon -- a Triangle with a + in the middle of it
You can select these icons (note that if the icons are in the same spot, you'll need to hover-Tab-click to get at the Survey Point) and once selected, toggle them between clipped and unclipped modes.
Let's look at the different modes of these two icons.
Survey Point
First of all, let's look at moving the Survey Point icon around. In its clipped mode, moving the Survey Point moves Shared Coordinates around. If you never move the icon in unclipped mode, this will set the origin of Shared Coordinates. This way, you can coordinate your 0,0 point that your CAD or BIM consultant team is using using Shared Coordinates. This is a very useful new feature in 2010. Note that if you acquire the coordinates of a linked CAD or RVT file, this will move the clipped Survey Point icon as you might expect. If you have linked CAD or Revit files inserted via Shared Coordinates, moving the clipped Survey Point around will also relocate those linked files.
The unclipped mode allows you to move the Survey Point away from the 0,0,0 location of Shared Coordinates. When you export your Revit project to the new .ADSK interoperable file format (big R > Export > Building Site), the origin in that file will respect the location of the Survey Point whether its location is clipped to the Shared Coordinates origin, or unclipped and moved away from the Shared Coordinates origin. Note that in the unclipped mode, the Survey Point icon shows the X,Y and Z offsets of the Survey Point with respect to the Shared Coordinates origin. There doesn't appear to be any way to move the Survey Point back to SC 0,0,0 except by typing 0 into each of the N/S, E/W and Elev fields.
If you're not working with the ADSK file format, then you'll always move the Survey Point icon in clipped mode. You'll need to move it in plan to set the N/S and E/W (X and Y) origin for the site, plus in an elevation view you'll need to move the icon vertically to geodetic Sea Level -- and then I would create a Revit level datum (and plan view) at that same elevation for bringing in the topo from the surveyor so your terrain model will be built at the correct elevation with respect to your project.
Project Base Point
As of Revit 2010, you can unclip and relocate Project Coordinates without moving your level datums. This is a huge increase in functionality as you can move them in X, Y and Z. But let's look at the clipped mode first.
In clipped mode, moving the Project Base Point moves the project with respect to Shared Coordinates. Project Coordinates are not being moved. So moving the clipped Project Base Point down 50' is like moving the clipped Survey Base Point 50' upwards. When moving the clipped Project Base Point, the Shared Coordinates origin (the Survey Base Point) stays where it is, and you move the project with respect to the Shared Coordinates origin. Revit's help files say that moving the clipped Project Base Point is the same thing as using the Relocate Project tool.
In unclipped mode, moving the Project Base Point moves the Project Coordinates of the project. So when you export the project w.r.t. Project Coordinates, moving the unclipped Project Base Point will change the Project Coordinates origin. However, this does not affect the cardinal rule about modeling your project within a one-mile radius from the startup location of Project Coordinates. Revit's help file instructs users to confirm that the model is within this radius. If the PC origin has been moved in this manner, you can return the Project Base Point back to its original location by right-clicking on the unclipped icon and from the right-click menu choosing "Move to Startup Location". The startup location of Project Coordinates cannot ever be changed, and your model must be built within a one mile radius of this point. Note that in Revit 2011 the limitation has been lessened: you may now design inside a 10-mile radius around the startup location -- a substantial improvement for larger projects!
The ability to move the unclipped Project Base Point solves some problems for our office. In our template, we set the main floor to 100' Project Coordinates (so subgrade storeys won't have negative level datums), and Shared Coordinates is the geodetic elevation of the project. However, when exporting to Google Earth, Ecotect, or other apps, the project comes may come in 100' too high because exports like these seem to deal with Project Coordinates rather than Shared. So now you can try unclipping the Project Base Point and move it to your main floor elevation, export, then move it back again. Note that the Globe Link export utility looks at your project and exports based on the Startup Location of Project Coordinates, so moving the unclipped Project Base Point will do nothing for this workflow.
So all in all, this new functionality is welcomed, even if it is a little confusing. I hope this treatise helps someone out.
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
Great tutorial Wes! Thanks:beer:
Andre Carvalho
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
Thanks Wes. There are some points which I'm not sure I fully grasp/agree, but I'll post back if I find otherwise.
From the Beta posts, I recall that it's not important anymore WHERE the project is modeled with respect to any origin (I even have graphics posted by Autodesk illustrating this). What is important is the "bounding circle". In other words, all your geometry has to fit on a giant, 1 mile radius plate, regardless of where the plate is located. I have not tried exporting to ADSK yet, but it seems peculiar that such export would behave differently than a dwg. I would expect that if the Survey point is not at the Shared Coordinates origin location, that the export respects the origin regardless of the icon location.
Finally, the icons mentioned have their own sub-categories in V/G (under Site), so instead of using the Reveal Hidden elements tool, you can just turn on/off the sub-category from the dialog. Just clarifying :)
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
A-ha! thanks Dave -- I'll edit my post vis-a-vis visibility.
The cardinal rule about modeling within the two-mile diameter circle is the main gotcha you have to watch with Revit. That hasn't changed -- you gotta stay on that plate ;-)
The help files actually note that the ADSK file format uses the Survey Point as the origin, and they have a matrix of clipped and unclipped Project Base and Survey Point behaviors which touches on that behavior (see: Revit Architecture 2010 User's Guide > Working with Linked Models > Shared Positioning > Project Base Points and Survey Points > Moving Project Base Points and Survey Points; and also Interoperability > Export > Exporting Building Sites > Export Settings for a Building Site > Reviewing Location Settings for the Building Site)
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
Thanks Wes. I'll read up on those topics and continue updating my notes!
As to what has changed, prior to 2010, you had to model within the 1 mile radius with the origin being at the fixed Revit coordinate system origin. If any of your geometry fell outside of this circle, you faced problems, even if your building footprint was 100' x 100' for example. That is no longer the case. Are we on the same page?
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
I think -- based on a thread during the beta -- that Lilli Smith or someone said that the original two-mile radius constraint continues; I wonder who we'd tap to find that one out? If no one from the Factory posts here to confirm I'll e-mail David Conant and see if anything has changed here.
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
The geometry of the model still needs to fall within 2 miles of the PROJECT basepoint. The survey point can be anywhere.
There should be some "Skill Builders" videos released soon covering this topic and how the information can be shared with Civil 3D via the ADSK file. I am not sure when these will be released but I will keep you updated when I hear they have been released to the web.
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
So Jeff, are we talking about the startup basepoint, or any location that the basepoint is moved to? So if we move the Project Base Point a mile away from the startup location, isn't that going to be a problem? I assume that the caveat about model positioning is with respect to the startup/original location of Project Coordinates...
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
Quote:
Originally Posted by
Wes Macaulay
So Jeff, are we talking about the startup basepoint, or any location that the basepoint is moved to? So if we move the Project Base Point a mile away from the startup location, isn't that going to be a problem? I assume that the caveat about model positioning is with respect to the startup/original location of Project Coordinates...
This is correct. There are really 3 coordinate positions. The Survey Point, used to share positions between projects and other applications. The Project Point is used to establish sport coordinates, elevations, etc... within the project. The 3rd point is the Revit interanl coordinates not exposed to the user. This is the point that the 2 mile limit applies to. clear as mud right? I hope the skill builder videos make this a little more understandable on how you wrok with these different points.
Re: Project Coordinates, Shared Coordinates, and the new Survey Point
Well, if that hidden internal coordinate system is the Startup Location of Project Coordinates, then it's not really that hidden ;-)
One more clarification: exporting to the ADSK file format -- this is always done with respect to the location of the Survey Point, whether it's clipped (at the origin of Shared Coordinates) or unclipped?