Using a Feature Line as a Corridor Target in Civil 3D 2009

There are heaps of nifty new feature line tools in Civil 3D 2009 that will make your grading life a whole lot more fun. One of my favorites is using a feature line as a corridor target. Think of all of the times you would love to grap elevations to drive your model but it seems redundant to make another alignment and a profile, especially when you already have a feature line drawn.

Read on…

I made a feature line that reflects some lot grading. Perhaps this is a feature line that I am using to drive some grading objects- or some of the new relative elevation feature lines (a post on that one soon to come!)


I added a LinkWidthandSlope subassembly to my assembly which I will hook on to that yellow feature line. Note that ANY subassembly that will accept a target can do this- there are infinite possibilities!


There is a new user interface for choosing target alignment and profiles. Note the options- you can use alignments, profiles, survey figures, feature lines or polylines. Wow…


I add my feature line as both a “Width or Offset” target and as a “Slope or Elevation” target- and it works great! Any edits to my feature line will make my corridor out of date, and upon rebuild everything will ripple.


My mind is humming with ideas- how about yours?

**Note that feature lines that have been dynamically extracted from corridors (also new to 2009) cannot be used as targets in corridors. The possibility for circular references would be too hard to resolve.

Here is a peek at that delicious little option as food for thought:



  1. John Davis says:

    Since gravity sanitary sewers and floodplains determine minimum Finished Floor elevations, an approach of lot grading to surface stormwater considerations controling roadway elevations would seem to be a simplified process by this new ability. The necessity of controling cfs slips into the drivers seat and now there’s added flexablity for such approaches. Considering the frequency of flash flooding in our over-developed, strip mall, mega-center obsessed towns and cities, it’s not a moment(Tc or Tp) too soon. SOS must stand for Save Our Shopping!

  2. John Davis says:

    Well, I guess you didn’t say the feature line could push the roadway up or down… and I can’t seem to find the “unsend” button (again)!

  3. John Cobb says:

    The very need John Davis cites arose as my corridor and floodplain converged. The corridor was in 20 ft. of rock cut as it approached intersection with a federal highway. I wanted to remove the remaining mound on the low side of the corridor for a construction equipment staging area. I laid a feature line at existing elevation along the floodplain boundary. Offsetting that feature line horizontally & vertically (for wiggle room), I created an alignment w/ profile (I was using C3D 2008) to target with a link that allowed multiple gradients. This allowed me to grade a staging area relative to the roadway and tie into my target alignment/profile, thus protecting the floodplain. I made this target system a part of the corridor to update dynamically. With Dana’s tip on 2009’s new target interface facility, this process will be greatly streamlined.

  4. I am sure that John Cobb’s methodology combined with some of the new 2009 features could be used to push the corridor “backwards” from the lot grading/flood plain as well. You’d just have to mess around with your subassemblies, baselines, targets, etc.

  5. mark mcguire says:

    Nice website. First time post – does this option allow you to define a subassembly section (depth) between the feature line and the subassembly line? Your example reminds me connecting a subassembly to a daylight feature line. Don’t know if I’m using the right lingo, but I’m curious if the feature line varies in distance from the assembly line, can you use this as a way to define an odd shape section and then accurately calculate volumes for unusual geometry, etc.? Been looking through the previous posts about corridors and using odd shape alignments, profiles, and assemblies rather than feature lines to grade a site – but the odd shapes seem to be interpolated by the tin between subassemblies like curb and gutter – so tis dead space has correct grades but technically no section defined. So cross sections will show your curb and gutter, but not the road section.

    Just trying to find the most ways to dynamically link my model to quantities while allowing for multiple design iterations with confidence that everything that can be updated automatically. The more automation the better!