Alignments and Profiles, Keeping in Sync

Ed Note: Steve Boon, the first of our guest contributors, weighs in on Alignment and Profiles. Please, let me know what you think! Should we bring him back for round two? It’s a tough room…. JW

You’ve built a really good roadway alignment – nice smooth curves with enough tangent between them to allow the superelevation to work, and a profile that balances your cuts and fills effectively. Great – but then the client wants you to “move the first PI over here, and change that radius.” After you have done this you have to go back and fix the profile because the length of the alignment has changed.

This problem has been annoying me for a long time now, and I have seen enough discussion group posts and wishlist requests to know that it is an issue for others. Autodesk may be working on a solution but in the meantime here is my workaround. I can’t take all of the credit – I actually stumbled into this because I was half asleep and misread one of Dana’s posts.


– Select the alignment, right-click and choose Alignment Properties. Select the Station Control tab.

– The upper right area of the dialog shows the current start and ending chainage while the upper left shows the coordinates of the reference point, and the station used at that location. If you haven’t changed these values previously then the coordinates and station are at the start of the alignment.

– The trick is to change the change the reference point and station to the OTHER END of the alignment. Select the icon to the right of the reference coordinates, and using snaps pick the endpoint of the alignment. Cvil3D will warn you that this is a bad idea, but hit OK to continue. Now change the station to match the end value from the upper right area of the dialog. Again Civil3D will warn you. Carry on and then select OK to exit the Properties dialog.

Now try editing the alignment. As you change the length of the EG profile the endpoint of your design profile “sticks” to that station, while the start point moves. You may have to edit the profile view properties and set the start and end of the grid to a large enough range to allow the left end of the design profile to display.

This solution works best when you have to make edits near the alignment start and it will change your start station, which some people don’t like. It’s not the perfect answer – but it does help.

Note to self: Re-read some more of Dana’s posts before bedtime.

Comments are closed.