We currently use GEOPAK SS3 for processing surveys and producing/editing terrain models. I am not quite comfortable/ready to use SS3 for Roadway Modeling, etc., at least not for production work. The Terrain Editing process is simply much easier in SS3. Once I am finished editing the terrain model I then export it to a GEOPAK TIN file for downstream applications (GEOPAK Drainage, SS2 corridor modeling and plans production, etc.)
My exact workflow is this:
1) Use Survey SS3 to generate terrain model.
2) Immediately export initial terrain model to TIN prior to any editing.
3) Create new terrain model in a new dgn by importing this TIN file as the source.
4) Make any necessary edits and re-export to TIN file with same name (overwriting original TIN file). This way if I need to update from source for whatever reason it will be somewhat current.
This process ensures that any terrain model edits are not lost since since any change to the terrain model's Edge Method (i.e. Edge Length change, Edge Method change) effectively reprocesses all of the triangles, undoing any edge triangle deletions, triangle swaps, or other terrain model edits. (I found this out the hard way!)
Regardless of what I use for source data for a terrain model I should be able to expect that a TIN file produced from GEOPAK SS3’s own "Export to TIN" command would produce a TIN that is identical to the terrain model. However, this has not been my experience. At the end I would like a TIN for use in SS2. I don’t think it is unreasonable to expect that the exported TIN should match the terrain model.
Has anyone had a similar experience with Terrain Models not matching the exported TIN?
Josh Mauritz
In these pictures the top one is the terrain model and the bottom one is the exported TIN file.
Looks like breakline and edge triangle issues.
Sometimes the crews shoot random spot grades where a breakline would have been better. Does the exported tin show all the same breaklines as the original surface?
Charles (Chuck) Rheault CADD Manager
MDOT State Highway Administration Maryland DOT - State Highway Administration User Communities Page
Thanks for the reply CaddCop. I agree with your statement about crews sometimes shooting points where a breakline might have helped bettetr define the surface. However, there will always be at least a few times where things don't just triangulate the way you would like. That is a perfect example of why you would edit a terrain. Usually I can swap a few triangles to get the contours to look right.
The real problem, in my mind, is that regardless of how much or how little editing was done to the terrain, the resulting exported TIN file should be an exact copy of the triangles, which is not the case in the few projects I have checked since I first discovered this.
When I compare breaklines in the terrain vs. the TIN, they look to be the same. What jumps out at me is that any vertices that I added to the terrain show up the TIN, but the problem is that several of the triangles that I flipped in the terrain don't appear flipped in the TIN, and several edge triangles were added to the TIN that I had deleted from the terrain.
Josh
I have found that within InRoads, flipped triangle faces are not persistent. To preserve them, you must lock triangulation. If you later need to edit or add to the surface in any way that requires re-triangulation, the flipped triangles are lost. The same is true of deleted edges. At least with those, I can display the exterior limits and import that as a boundary.
On one project, I found it necessary to add breaklines to preserve the flipped faces. But I also discovered that re-triangulation with these new breaklines, frequently effected other triangles in the area of the flipped faces/added breaklines. It was kind of maddening.
On the Autodesk side of things, flipping faces adds editing records to the file, and if the surface is re-triangulated, the faces get re-flipped from the edit records which effectively preserves them.
My general rule of thumb is - flip faces only when you are 99.9% sure there will be no additional edits required.
Since you keep mentioning TIN's, I assume you are in a GEOPAK SS2/Ss3. While I have some GEOPAK experience, it is pretty rusty so I cannot add any additional GEOPAK specific insights. But it might be a similar issue.
The only way I found to guarantee triangles did not move was to import their edges as breaklines. But that really makes an impossible to edit surface. OK, not impossible, but such a move needs to be a last resort and made on a copy of the surface in case you need to go back.
Have you tried export to and import from LandXML?
Neil Wilson (aka Neilw)
Power Civil v8i 08.11.07.245
AutoCAD Civil 3D 2018