More DTM Questions

[Jean-Marc]

Further to my previous posting, I upgraded to VW 10.0.1, and was subsequently able to generate a DTM. However, in that first attempt, the 3d contour lines closed in on themselves and created some false topography. I deleted the first model, recreated my 3d contours, and tried again. Now, I get an error message indicating that NNA_DTM-Hidden Record could not be found.

1. How do I prevent contours from closing in on themselves?

2. What's up with the error message; there are no duplicate or overlapping contour lines in the layer.

[Guest]

Jean,

Once you've created an existing DTM, you cannot re-create it in that document.

What do you mean by the polys closed on themselves?

[Jean-Marc]

Thanks Katie,

1. If I want to create a DTM, can I just save the document as a new document, or do I have to copy and paste the whole document into a new file?

2. Re: the enclosed contours: In my 2d topo map, I have 8 contour lines, all of which extend outside the site boundaries. In other words, none of the contours are closed. However, in the model, the contour lines did close in on themselves with a straight line that connects the opposite ends of each contour (it looks like the line follows the polygon fill area).

[Jean-Marc]

I just copied the layer with my 3d contours into a new document to experiment a little, and to recreate the problem I had with the closed contours.

I think I'm doing everything as I should, and yet, the resulting DTM is wonky. Some of my contour lines do seem to close in on themselves. As well, the model did not include 5 of the 9 contour lines.

[Guest]

Email me this new file to

tech@nemetschek.net

Subject: Attn Katie

I'll look at it and get back to you.

[Robert Anderson]

The Digital Terrain Modeler creates a TIN (Triangulated Irregular Network) of points derived from the data you provide in your source layer. It then generates the Site Model symbols from this TIN. The Site Model will not "match" your contours unless you set the vertical contour spacing in the DTM to match that of your data. You do this using the "Settings..." command on the AEC:DTM Processor submenu.

As of the next maintenance release (due out Real Soon Now), you should be able to re-use data as the Site Model command will be a little "smarter" about how your document is organized.

I too would like to see your data, so if you don't mind, email me a copy as well. randerson@nemetschek.net

Thanks.