How to set a Civil 3D alignment to measure curves by chord

by Timothy Corey

Today's issue has to do with the way Civil 3D measures and reports curves lengths. In most instances engineers want lengths reported along the arc, but in certain cases, especially when working with railroad alignments, the engineer wants lengths input and reported along the chord. 

Here's how to set that up:

If you are creating a new alignment, on the Create Alignment - Layout dialog, just below where you input the alignment name, note the Type dropdown. If you drop this list down, pick the Rail alignment type. Next, create your alignment as you normally would.

After creating the alignment, select the alignment and go to Alignment Properties. Activate the Station Control tab. Because you set the alignment type to Rail, on the Station Control tab, you will have an option to Measure curves along chords.

If you have an existing alignment whose type is set to Centerline, go the the Information tab of Alignment Properties to change the alignment type to Rail and then go the the Station Control tab to turn on the option as shown above.