On those rare occasions where you have to build up a topo manually, some of you may have noted the following.
If the Z value of Revit's shared coordinates is the same as the project Z value, there is no problem.
But if you're using shared coords with a Z offset from the project coords, then you get this problem: let's say you've left your main floor elevation at Z=0 for the project elevation, but to relate to the real-world elevation of the project, the shared coords Z value for your main floor is really 623.15m.
The survey drawing (also in meters) you've got is flat -- no 3D points or plines. So you think, I'll just enter the point data in manually: they're right there on the survey which you've imported into your site plan. So you switch the project units to meters and start entering in the points in the toposurface command, but you realise right away that the points are coming in too high.
You bet they are: 623.15m too high. Topo points in Revit work only with project coordinates, not shared coordinates. So you either have to subtract the base elevation of your project from each COGO point in the site plan (yuck), or wait til you're done and move the topo down 623.15m
And when you're editing the grading you'll have to knock 623.15m off the Z values of the points you add or edit.
Fortunately the spot dimension tool allows you to report in shared or project coords, so that's cool.
I said all that to say this: I would like the option, when editing or adding points, of choosing project coords or shared coords.
All those who understand this horrible post and need this feature say AYE!.