I am having problems editing triangles. There are spots in my project where a high line rail crosses a road. There is about 30' difference in elevation. In top view, the vertical plane makes it difficult to use the edit surface> delete triangle. I wrote the triangles to the design file and made the appropriate voids. I don't want to import the triangles as a feature and re-triangulate. Is there a way to import triangles into a surface?
To model a surface where one road or rail line cross over a lower area, you need to model the lower area in one surface and the bridge area in another. We speak of imagining a giant reached down and lifted the bridge off of its abutments and piers, although to model the DTM you also need to ignore the piers, too.
DTM software does not allow more than one Z elevation to exist in a single surface for a given XY location. Most people think of that as points, but it really applies to points or triangle faces. No triangle faces can be vertical, or reverse sloped, as in an undercut bank. Does this make some real world situations more difficult, yes. But the alternative would be for a DTM to be this very complex solid of meshes and splined curves and some of the earlier PC's would never have been able to work with the data.
Charles (Chuck) Rheault CADD Manager
MDOT State Highway Administration
I'm not concerned with anything under or beyond the overpasses. I understand about undercuts and no vertical triangles. The road lines were trimmed to the bridge deck and there should be no conflicting elevations. I want to import my own triangles without re-triangulating, or have a better tool for isometric view triangle editing.
If the triangles were built by features, editing the features can generate good results.
The edit feature point and place feature tool allow you to manipulate the features which ultimately generate the triangles.
Importing triangles is only slightly more desirable than importing contours. To preserve the exact triangulation, you must import them as breaklines. If you ever need to edit a surface in any way that was created from imported triangles you may seriously begin to consider homicide as a justifiable action to perpetrate on the person who created the mess you now need to clean up. Been there, Done that, Absolutely Hated It.
I found it less work to go back to the original surveys an reimport them and merge them to rebuild a composite surface from photogrammetry and 6 or 8 subsequent surveys. Someone else had exported the DTM to LandXML, edited it in Land Desktop and brought it back into InRoads. The file was unmanageable by then when I needed to merge in a number of new surveys.
Cop...I agree with you. I would in this case make a separate DTM of the bridge deck. This method is standard procedure at firm and for our clients.