Overhang Correction - Corridor Surfaces?

[LeafRiders]

Could someone explain how and when I should be using "Overhang Correction" setting in my Corridor Surfaces? Or even mention a couple of cases where you've used in different instances to help me understand the setting a little better. Thanks.

[owenmull]

What the overhang correction is used for is to tell Autocad in what order to connect the codes  when it creates feature lines based upon your sybassembly. For example, in your subassembly, you have a vertical link. With no overhang correction, in drawing the feature line, Cad might draw over then top to bottom, but you want bottom to top instead. Overhang correction forces Cad to connect the feature lines by the order in which it drew the links. 

See the attached picture for clarification of the difference.

[owenmull]

Please excuse my stupid Paint drawing.

[LeafRiders]

I wouldn't call it stupid... Spells things out quite nicely.

I have a couple corridor surfaces that aren't looking quite right see attached. The stripping surface creates a top effect that combines one into the other but will act as a cut volume when I compare it to the EG_Surface.

The other issue I'm having is the datum surface for the road structure doesn't seem to be ending at the point at which the Subbase link ends, it continues on to no-man's land for no apparent reason. My boundaries are set to "corridor shrinkwrap" from the corridor boundaries, and the attached jpg shows my settings. Thoughts?

Both the stripping surface and the datum surfaces aren't quite right. Any idea on how to approach this? I might have to create a right and left stripping and compute separately if I can't get that top connection to not build when creating the stripping surface.

[BrianHailey]

When it comes to overhang correction, this image pretty much explains what's going on. If you add the DATUM links to a surface (and that's it) this is where the surface will be for the three possibilities. I used to tell people, "If you create a top surface, set the overhang correction to top and if you creating a bottom surface, set it to bottom" but I no longer tell people that because it isn't a very accurate assessment of what's going on.

http://screencast.com/t/5FXcJnVNTfDn

[BrianHailey]

Looking at your settings it appears you are adding two pieces of data that are directly above/below each other. If you are using the LaneSuperelevationAOR subassembly, then you are adding the bottom of the pavement AND the bottom of the subbase to the surface and it may be confusing it. Which subassemblies are you using?

As for the surface extending beyond the limits of the corridor, turn the display of the surface on (use a style other than no display) and see if it really does extend beyond. Sometimes when a corridor daylight intersects itself the corridor extents boundary fails.

[sboon]

You have run into the same problem that I did with surfaces where the design involves construction on both sides of the roadway but not in the middle.  I`ve posted a solution for this in another thread; essentially what you do is use stripping subs with a minimal depth all the way across the section, and then add two more stripping subs from the existing shoulders outward.  When you build the stripping surface the bottom links option is used to create a surface that includes the entire section but only cuts into the shoulders as designed.

[LeafRiders]

The subassemblies used for the pave and subbase are LaneSuperelevationAOR and ShoulderExtendAll. The stripping surfaces is setup with LinkOffsetOnSurface and target the existing Side slope and Daylight Feature Line is set off the TopSoilStripping SA.

I had the corridor surface set to be the boundary and that was throwing the datum surface out to extending to a random point. That seems to be fixed... The main issue is try to create two separate Stripping surfaces one on the Right and One Left. I'm not sure I gather your stripping solution to eliminarte that false top that's shown above. I'll look for your other post... At this point I will rerun the stripping with separate corridors and try to establish two separate surfaces. (a little annoying). Thanks for the input fellas.

[sboon · Accepted solution]

I've attached a drawing with a simplified example of how this assembly can work.  If you check the corridor properties and view the sections you will see how the stripping surface is built.

[LeafRiders · Accepted solution]

I ended up using a stripping depth value of .0001 and that gets rid of the top affect when using bottom links (or top) doesn't seem to matter. I use the Stripping link and Top or Bottom links for overhang correction generate the same Surface that seems to be having some issues. I thought we had but obviously something is off on the surface side of things. The blue is the corridor and the Orange line is the surface line. It comes up short when defining the surface. See image

Any other settings or tweak suggestions?