Station Equations do what? to my alignment?

Update: Noticing this post gets a lot of attention. These hiccups have been addressed in more current versions, including 2010.

What are station equations and what do they do to my alignments? To quote one of my favorite authors, Phil Zimmerman:

A station equation is a point along the alignment where the stationing changes.  The equation can represent the meeting of two stationing systems or the chnage in authority over the centerline.”


So that’s the definition, but why does this matter in Civil 3D 2008? Surely, this is inherant functionality?  Read on for more detail….

Yes, this is inherant functionality and has been there since the begining.  What’s unexpected in 2008 are a few things.  Let’s say you want to add design speeds along the alignment for various reasons. You get the following interface:


The rub comes when you want to add a design speed at a station beyond the equation point.  Specifically, the issue arises when the design speed is placed beyond the physical length of the alignment, but before the adjusted ending station. OK, let’s cut to an example.  We have an alignment that is just over 232 feet with an equation back @ 0+62.47/ahead 40+00.


Let’s place a design speed at 2+50 by typing the value. You get this message:


However, if we actually pick the location, it works!



OK, so that’s a gotcha to look out for…. Now what was i saying about sections?  In the section view style, the sample line name is used when a station equation instead of the raw station.  When you create the sample line group, the sample line name function will double the equation adjustment (37.53*2 in our case) for the ahead stations.

slg1.png        slg2.png

However, the properties of the sample line indicates the correct station…  Autodesk is also working on this as well….  What is the workaround? Not use the Sample Line Name but the Sample Line Station Value in the Label Style.

slg3.png      slg4.png

Hope this helps!


About Kevin
Hi… I am a husband, father, brother and neighbor. I am employed as a Civil Engineer and have enjoyed playing the drums for the last 30+ years.

One Response to Station Equations do what? to my alignment?

  1. Pingback: 2010 in review « Land Development Engineering

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