Site Topo Problems

[rutt45]

I have been struggling with an attempt to import, or build, a reasonably accurate topo.

My site has parking, retaining walls, and some gentle slopes.

Revit seems unable to recognize the idea of a retaining wall.

And points placed directly on contours result in generate contours in completely different places on the topo.

Any suggestions, best practices, things to avoid?

[greg.mcdowell]

If you can create your topo in another application, one designed for this purpose ideally, and import that you'll be better off.

Topography, and site work in general, isn't something Revit does well. It's good enough for relatively flat sites or for showing the fall of the land at a macro level but I don't put much stock in it beyond that.

You can make a lot of site elements from standard Revit tools - walls, floor, and sweeps for both are your best bet - but, again, if your site has a lot of slope you're probably going to be banging your head against the wall before too long.

[d.stairmand]

We generally make them up using the Surveyor's Points - Not there Contours.
The Points are Exact - The Contours are the Surveyor's programs Interpretation of those point. As Revit is a different program - they always turn out different.
We then added walls for Retaining, Floors for paths etc.

[petebalf]

the main thing i learnt was in order for a vertical drop, i.e. a vertical retaining wall, I needed to split the topo, make another topo surface. It was one of those 2am eureka moments.
peter

[oliveoil182411]

Not a Revit user, but I have worked on several site /topo plans when I worked for a civil eng. firm. Greg.mcdowell may be correct in saying that you should use another application to generate the contours. However, I had to create several retaining walls in the past, and they always created trouble when generating contours even though I was using a civil package. The trouble was that the program would see the surveyors points(if it was a topo) or proposed grading lines(if it was a site/grading plan) for the top and the bottom of the retaining wall, and then interpolate between the two. This would just create a steep slope. The fix for this effect was to draw a 3DPOLY along the top points of the wall. Also, I would draw another 3DPOLY along the bottom points of the wall. In plan, these 3DPOLY's should look like offsets of the centerline of your wall. If you don't have sufficient surveyor points on the existing wall, get some! However if you are a good guesser, you can add points to the 3DPOLY for the model to grab elevation information from (this is not good practice). If this is a site/grading plan, the method is the same. However, you will be drawing your 3DPOLY to points along the edge of your grading, both top and bottom of wall. This allowed the program to see the "break" in the two elevations and us to have one TIN or model of the topography. I have attached a simplistic example. Hope this helps will work for Revit.

[rutt45]

the main thing i learnt was in order for a vertical drop, i.e. a vertical retaining wall, I needed to split the topo, make another topo surface. It was one of those 2am eureka moments.
peter

This was the best suggestion I've gotten: I certainly understand the "2am eureka" reference!!

I ended up breaking the topo into eight parts - multiple retaining walls!! But at last I have a reasonable representation of the site: not great, mind you - just reasonable.
Boy does the topo routine need to be reworked! It's not just different software giving different results - Revit yields incorrect results with no rhyme or reason.

Anyway: thanks for the help!

[Alan aka cadalot]

here is a link to some guidance notes I put together for our Revit users

http://cadalot-revitlearningcurve.blogspot.com/2007/08/guidance-note-toposurfaces-introduction.html

The top left corner of the topos on the first page is a railway tunnel entrance up at the olympic village in London.

You will see one was made by selecting points and the other by using a 3D AutoCAD drawing.

[oliveoil182411]

here is a link to some guidance notes I put together for our Revit users

http://cadalot-revitlearningcurve.blogspot.com/2007/08/guidance-note-toposurfaces-introduction.html

The top left corner of the topos on the first page is a railway tunnel entrance up at the olympic village in London.

You will see one was made by selecting points and the other by using a 3D AutoCAD drawing.

I am not a Revit user. However, I am curious, do your users use 3DPOLYS in autocad to define retaining walls and other sharp elevation changes prior to importing it to Revit. The one civil package that I used, when I was doing civil work, produced descent results. And it was rare that we had to produce more than two topographic models (one for the existing grade and one for the proposed grade) for the same site.

[Alan aka cadalot]

No work was done to the AutoCAD drawing by us it had the 3d information contained within it which had created the contours.

Re retaining walls when undertaking the flood risk assessment on a proposed site we used pads set above the surrounding ground to give the profile of the buildings on the site, I can't see why this could not be done for retaining walls.

The graphics are animated if you click on them and enlarge the thumbnails.

[oliveoil182411]

No work was done to the AutoCAD drawing by us it had the 3d information contained within it which had created the contours.

Re retaining walls when undertaking the flood risk assessment on a proposed site we used pads set above the surrounding ground to give the profile of the buildings on the site, I can't see why this could not be done for retaining walls.

The graphics are animated if you click on them and enlarge the thumbnails.

Cool graphics. It good that you had some compentent civil guys coordinating with you. Maybe the original poster needs to talk to some civil guys that provide models for Revit users on a regular basis. My guess is that Revit's topo application works very similarly to the more specialized civil packages. That is why I originally suggested using 3DPOLY's for defining a retaining wall. Anyway, it seems as though Rutt45 has found a solution in the multiple topo idea(I did this as well before I started using the 3DPOLY's). It just seems like there would be a better way than to keep track of 8 different models. Best of luck Rutt45.