Toposurface problem

[bob.86982]

When I import a topo drawing from my surveyor and create a toposurface over it selecting his contour layers only, the created surface does not match his exactly.The contours on the toposurface are offset approximately 0.75' horizontally and in some places the toposurface contours become jagged and very irregular. This has happened on every project I have done in revit and I have done everything I can think of with the file before importing it to try and correct the problem.

His topo drawing looks great in the project in the site plan and 3-d views but I can't edit that for graded regions, split surfaces, etc.

Doe's anyone know if there is a way to correct this problem?

Thanks,
Bob

[mickaeL_renauD]

Are you importing ppoints or is it a CAD file?

I just got finish my first site with using a mixture of programs to get it to look and work right(from GIS > Autocad > Revit)

Let me know what file format you using...

Cheers!

[bob.86982]

I am using a cad file and in the create toposurface command telling it to use the contour line layers to generate the toposurface on.

Bob

[mickaeL_renauD]

What are the steps you taking after you import the cad file...?

[bob.86982]

Pick Site menu
Pick toposurface
use import-import instance
pick on the import
in the add points from selected layers dialog check contour and index contour layers
finish surface

Bob

[gordolake]

Bob, it has to do with the triangulation that revit uses between the points that are associated with each line from the contours in the CAD file.

You may be able to adjust the topo surface in revit by adding extra points to the surface over the top of the imported site plan contours.

If you go to visibility and turn on triangles you can perhaps see where they need to be added to smooth the contour. Sometimes you need to add intermediate point between the contour incriment to fix it up.

Site tools in revit need an overhaul, smooth contour splines would be great and the ability to control the surface by draging contour line vertex would be great. Hope this helps.

Steve

[bob.86982]

Steve,

Thanks for the info. I was starting to come to that conclusion about the triangulation but I hadn't thought about looking at the t-mesh to see how the contours related to it. There are thousands of points in this surface so editing points gets to be a huge job. My surveyor has told me he goes in and does some smoothing of the contours after they are generated by his program. I wondered if that could have any negative effect on the surface generated by revit.

I'll bet it's nice in Australia now, it's cold and snowy here in Southwest Colorado.

Bob

[Gadget Man]

When I import a topo drawing from my surveyor and create a toposurface over it selecting his contour layers only, the created surface does not match his exactly.The contours on the toposurface are offset approximately 0.75' horizontally and in some places the toposurface contours become jagged and very irregular. This has happened on every project I have done in revit and I have done everything I can think of with the file before importing it to try and correct the problem...

Bob, the most important thing BEFORE you import your DWG file is to make sure that you have your Site Plan level (project) based on a DATUM level (shared) which is at "0.0" height.

After that, go to DWG survey file in AutoCAD and make sure that the contours there have their "Z" values set correctly. I always re-scale surveyors DWG file to 1:1, so there is no mistake in scaling.

So, if the DWG file has a contour (say) "100" with a "Z" value=100.00 (elevated 100.00 above 0.00) and you import it into REVIT into a level (say) Site Plan which is based at 0.00, your contour line will be indeed at 100.00 and aligned with DWG contours.

P.S. If you (or anybody else) are interested, I have prepared a tutorial which includes basic DWG survey file preparation explained, as well as some aspects of Revit toposurface editing, in a PDF format. It is just over 3MB so I can't attach it here, but let me know if you want it.

[tomnewsom]

You could also consider asking your surveyor for the point cloud data, so skipping out the intermediate creation of contour lines. We've done this in the past.

[bob.86982]

Jerry,

Good points about setting up the DWG file. I would be very happy to have a copy of your tutorial. Thank you very much!

Bob

[bob.86982]

Tom,

I'm not real sure what you mean by "point cloud data". I assume it is just a points file?

Bob

[Gadget Man]

Tom,

I'm not real sure what you mean by "point cloud data". I assume it is just a points file?

Bob

I think he means just a txt file with the spot levels and their coordinates in a comma-delimited format.

Revit works with that very well indeed but sometimes it's hard to obtain such a file from the surveyors. For some reason sometimes they treat it top secret... ;) Also, a DWG survey file includes loads of other data as well, like existing trees, services, buildings, roads, and boundaries. It's all very usefull...

[tomnewsom]

A friend of mine made this fairly useful Autocad utility.

How to use it:

Scale the survey drawing so that the units are the same as those used in the vertical height spot levels (eg if the spot levels are in the format 16.345m, then scale the drawing to 1 unit = 1 meter)

Isolate the layer that has the spot heights on, copy all and paste to a new drawing

Run the utility.

It ouputs the coordinates of each text object, and the contents of that object, into a txt file.

With some search and replace in notepad, and renamed to csv, you can get that data into a revit-friendly form.

Works for me anyway!