Civil 3D 2009 - Surfaces

[348PATTERSON]

Good Afternoon,

I work for a small firm in Lititz PA and we are using Land Desktop still but looking to switch to Civil 3D. Our office has purchased C3D2009 and the CAD guys are to learn this in there spare time aside there project work. In doing so, I am creating an existing surface and am fine tuning it to have it look correct. We have taken a survey from LD2005 and are to generate an existing terrain from it. No there was no surface created in the 2005 version. What I am basically doing is starting from scratch. The LD2005 file was imported into C3D2009. It has Civil Point Objects provided by the surveyor as well as Polyline Contours with elevations. I have the surface 85% done. I am running across a situation where there is a break in my tin surface. Please see attachment (surface.jpg). Yellow/green represents Polyline Contour provided by surveyor, brown represents the tin surface contour created by C3D2009, and white/gray represents the triangles of the tin. If you view the image you can see that between points a & b, C3D is not creating a contour there. I have tried adding a line to the surface from a-b, b-c, a-d, b-d and it just wont add it. The elevation for a-b is 330. The elevation for c is 328.87. The elevation for d is 332. Any ideas on how to get this filled? This is not the only place this happens. I have had it happen on other locations as well.

Thanks,
348Patterson

[sinc]

How did you create your C3D surface?

It looks like you added the contours created in LDD, in addition to the survey points. That would have been an error.

Your TIN lines are also not forming complete triangles. Did you try to use the Edit Surface -> Delete Lines option? I find it best to avoid that option as much as possible. It can get you into some hairy problems.

[348PATTERSON]

Sinc,

Yes to the contours because I want to mimic them. No to the points, only a few added manually via surfaces/edit surface/add point. As far as the TIN not forming complete triangles goes, is there a setting/tolerance to adjust for this? If so where? Why would I get partial triangles anyway? Sorry for all the questions.

Thanks,
348patterson

[sinc]

It's difficult to tell what you are trying to accomplish.

Building a surface from contours should be the absolute last resort, because it introduces the most error. Since you have other options, it is very strongly recommended that you do not use the LDT contours to build your C3D surface.

If you simply want to pull the surface into C3D, then the easiest thing to do is to right-click in Prospector -> Surfaces and select "Create surface from TIN..." Then browse to the TIN file in your Land Desktop project.

If you want to "start from scratch", as you said, then the surface should be built from spot elevations and breaklines. This might be more problematic, because in Civil 3D, the ideal way to do this means that your field surveyor collects the data using linework codes. If the fieldwork is already done, then this is somewhat problematic. If you have breaklines that were drawn in Land Desktop, then you should also be able to create a surface in C3D simply by adding the Cogo Points and the breaklines to a C3D surface. It's probably easier to just create the surface from the LDT project, though, as mentioned in the preceding paragraph.

There are even more ways. For example, you could use the TIN triangles, and add the 3D Faces to a C3D surface as Drawing Objects.

The easiest and simplest is to use "Create surface from TIN..." to create the C3D surface directly from the LDT project. But that will create a surface that can give you problems if you need to edit it in C3D. So it may not always be the optimal choice. But it's definitely the fastest/easiest, if it will work for your purposes.