Topic: Sta-Offset Labeling Problem

[dfarris75]

I am trying to get a station-offset label at a point that is so far away from the alignment c3d is having a hard time with it. I just get "no station found" on my cursor. It is at a point of the alignment where I have a bend with no curvature so I guess there is a conflict. Can I help c3d to recognize that there truly is a station-offset at this point without modifying the alignment?

[sinc]

Well, technically speaking, if you are on the outside of an angle point, there is no station/offset for that point.

Note that in the attached image, the entire wedge-shaped area is all at the same station in the alignment.  So there is no way to identify a point in that wedge using a Station and Offset.  It's a "dead zone".

To get around this issue, sometimes people create very short curves in the alignment, instead of using an angle point.  That eliminates the "dead zone".

[mjguzik]

You can call a point past a PI w/o curve with a Point On Semi Tangent (POST) in the form of PI +Sta, Offset to account for dead zone area outside or the inside duplicate areas.  It normally takes the notation of

"P.O.S.T. P.I. +25.6, 12.0' Lt."

Regards,

MJG

[dfarris75]

I don't want to add any curvature so I guess I'll go with the P.O.S.T. Do I give the + value and offset from that tangent point?

[sinc]

Yeah, that's what that "POST PI +25.6" is.  A Point on Subtangent (or semitangent), 25.6 feet past the PI.  Since the distance is positive, that implies that the measurement is along the incoming bearing, extended past the PI.  A negative number would imply that it is BEFORE the PI, and the outgoing bearing should be extended before the PI.

Of course, Civil-3D does not understand points on subtangents, so you'd have to do this manually, or by creating your own "subtangent alignment".

[dfarris75]

So in this case it would be noted POST PI + 50 (150' RT) correct?

[sinc]

I probably would not put a space between the "+" and the "50", but if I saw a label like that, I would understand it.

[dfarris75]

I didn't mean to put the space there. I was just typing all fast to get the post done. Thanks for the help guys.