Spot Elevation from Survey Point Gives Wrong Value

[Anonymous]

Hi Friends,

I am trying to mark spot elevations in plan view for underground piping. I need to mark the elevation from FFE which is 26.5'. I changed the elevation of the survey point to this value and set my spot elevation base to "survey point". However, the value being given is incorrect and I can't for the life of me figure out why. In one instance the value should read 24.92 since the base is 26.5 (26' 6") and the depth of the pipe is -1.583' (1' 7"). However, the value being displayed is 29.90. Even if I were to do the math backwards the value still doesn't make sense. Can someone please advise me as to what could possibly be the issue? I've tried changing the parameter for the base to "project base point" which produces the same results. Thank you! 

[Mirko.Jurcevic · Accepted solution]

Have in mind that everything in Revit is modeled relative to the Project Base Point. Objects are not relative to the Survey Point in any case.

Also, Project Base Point defines "relative zero level" for building, meaning on whatever elevation is placed, there will be relative zero, and Elevation parameter means "absolute" height.

Difference between spot elevation measuring from Survey Point and Project Base Point is that first one measures in absolute height, and the second measures in relative height.

I don't know do you have shared coordinates system set up, if not, and you are sure you can change Project Base Point on your own, then the solution is simple:

1. On the ribbon, use Manage > Coordinates > Specify Coordinates at Point command
2. Click on the Project Base Point
3. Enter 26' 6"

Now, you relative zero will be on 26.5', survey point will be on the absolute zero, and your spot elevation will measure absolute elevations.

If you want, you can read more information about Project Base Point here: 

https://www.engipedia.com/revit-project-base-point-explained/

[Anonymous]

Thank you!