Toposurface - Project Base Point, Survey Point

[Anonymous]

Hello!

Can anyone help me understand this? I practice in Colorado and my sites are always over 5000'. I do NOT understand how the toposurface tool is built in Revit. I just want a reliable way to do the following:

1. Model a toposurface based on Navd 88 sea level elevations that I get from a surveyor.
2. Display my first floor as 100'-0" in sections and elevations.
3. Show true sea level elevations in a site plan.
4. Only use one model. My brain is not that big.

My major gripe is this: Why can't a toposurface be based on survey point? If it could be, then you could make micro-adjustments to project basepoint to move your building up/down, and N,S,E,W based on site constraints. If a toposurface is based on project base point, you can't move the building without moving the toposurface, that seems like a major flaw. Am I missing something here? 

[Anonymous]

Oh and the passage is from "Mastering Autodesk Revit 2018" - Kirby, Krygiel, Kim, in a section on Toposurfaces.

[Corsten.Au]

Hi..

Even when you move the " Topography " Vertically up or down, those points will show the same elevation value..

check ...

that point is not connected to project base or survey point..

idea is model the topography , and move the ENTIRE TOP up or down to match with the height..

best luck.

[ToanDN]

Something like this?

[Anonymous]

Thanks, that's a helpful way of thinking about it. I think the passage from the book I posted was confusing me. Topography is not relative to Project Base Point. Maybe the book is saying "Revit Project Base Point" is not the same as PBP.

[barthbradley · Accepted solution]

FWIW

The Points that you place INSIDE sketch mode are always relative the INTERNAL ORIGIN of the Project, not to be confused with the Project Base Point. When you Right-Click on the PBP, you will see "Return to Startup Location".  If you want to verify where the Internal Origin resides in your Project, UNCLIP the PBP, Right-Click on it and press "Return to Startup Location".  The PBP will move to move to the Internal Origin. 

With that said, you can model your Topography any number of ways. It's not clear to me about procedure you used, but no matter; after you close out of sketch mode, go to Elevation View and move the Toposurface to the correct Elevation RELATIVE TO YOUR PROJECT.   For instance, if your Toposurface has a graded region on it representing the a building site pad, position that pad underneath your Project's building. 

TIP: Before moving your modeled Toposurface; first go to Elevation View and Place a Level at the INTERNAL ORIGIN (e.g. the ORIGIN of your modeled Toposurface).  Then when you move your Toposurface, move this Level with it.  This is the “Sea” Level. 

Now Spot Elevations have 3 "Elevation Origin" options: Project Base Point, Survey Point and Relatvie.  Use a Spot Elevation that is set to Survey Point when annotating your Toposurface. To get it that Spot Elevation to report accurately, place your Survey Point RELATIVE TO YOUR TOPOSURFACE. For instance, if your graded site pad is 100'-0' above sea level in the real world, then place your Survey Point 100'-0" lower than where the Toposurface's graded site pad is currently located in your Project.

If you used the above TIP approach, you can also use Spot Elevations that are RELATIVE to that “Sea” Level you created.  

[loboarch]

You can take a look at this video for some guidance. Might give you what you are after.

http://help.autodesk.com/view/RVT/2019/ENU/?guid=GUID-6A655821-3E03-4452-99A8-E74BFF677B06

[Anonymous]

Thank you, really good explanation.

[croundy5QGYD]

I've run into a similar issue.  I don't understand why the survey point isn't always pinned to the revit internal origin.  Its kind of misleading that you can move the survey point but your toposurface points still show their elevation in relation to the origin.  I agree they should be in relation to the survey point, or there should be instructions upon creation of a new project to relocate the project base point and all levels to the desired elevation above sea level.

[barthbradley]

When you insert a Model Family in the Project, do you always place its insertion point at the Internal Origin of the Project, or do you place it where it needs to be in relationship to the Project building model? I suspect the latter. It’s really no different with a Toposurface. The “zero” origin of your Toposurface/Points inside Edit mode is of no more significance than the “zero” origin of your Chair Family that you placed on Level 3. 

[croundy5QGYD]

Respectfully, those two scenarios are completely different.  Families have a relation to the level they are placed on.  You can't place a toposurface in relation to a level.  When you edit a toposurface it's points are always in relation to the origin.  As far as I know that cant be changed.

[barthbradley]

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@croundy5QGYD wrote:

Respectfully, those two scenarios are completely different.  Families have a relation to the level they are placed on.  You can't place a toposurface in relation to a level.  When you edit a toposurface it's points are always in relation to the origin.  As far as I know that cant be changed.

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No, they are not completely different - and yes, you can place a Toposurface relative to Level by moving it.  Lastly, 

regarding the Point Elevations shown inside Toposurface Edit Mode; let me reiterate that those elevations have no more significance in the Project than does that hypothetical Level 3 Chair Family's "Ref. Level" elevation. Still reads 0'-0" in the Family itself; right?   

You know what might find illuminating? The Revit Theory of Relativity: Understanding Shared Coordinates. I know it sounds unrelated, but download the PDF and give it a read.  I think it might make that lightbulb above your head turn on.  

Shared Coordinates Archives - Paul F. Aubin (paulaubin.com)

[croundy5QGYD]

Thanks barthbradley! That's a very helpful link concerning shared coordinates.  Unfortunately, it doesn't address the issue I've been experiencing.  I want one of my topo points to be 2043.84' ASL. Level 1 is at 2047.5' ASL (the survey point was moved using "relocate project").  The project base point is at the origin which is 100'-0" below level 1.  It takes some math to figure out the difference between the topo point 2043.84', Level 1, and the origin.  In this case to get my topo point in the right place I have to subtract 2043.84 from 2047.5 which equals 3.66' below level 1.  Now I have to subtract 3.66' from 100' which gives me 96.34' from the origin for my topo point. Fortunately, I've got an excel tool that will do the conversions for me but It would take half the time if I could type in 2043.84' from the survey point one time in Revit. Its easy enough to model a simple toposurface and move it, but I've found that moving an entire model after years of development is bound to cause some issues. I guess this should really be in the Revit Ideas blog as a request to Autodesk to provide the feature to allow toposurfaces to be edited in relation to the survey point.  Thank you for trying to help anyway.

[barthbradley]

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@croundy5QGYD wrote:

I want one of my topo points to be 2043.84' ASL. 

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I'm confused. This is about lowering ONE Point?  Not all of them?   Is this a recurring thing you have to do? That is, edit the Toposurface and change the elevation of one Point every so often?    

If that's the case, then maybe put the Toposurface in a separate file and Link it into the Parent Project. This way you can leave the Toposurface's Point Elevations relative to the Internal Origin in its own Project.