Grade extension of feature line

[rustee4u]

We are working on a road widenign scheme where one edge of the road is retained as far as possible while  other edge being  widened. I like to design  a retained channel line by extending the cross fall between the existing centre line and the exiting channel line on to the design one.

It is possible in civil 3d to extend the gradient between two feature lines at some offset  from reference feature line?

[troma]

Do you mean two feature lines that are roughly parallel, and you want to grade between them?
If so, use a grading. You can grade at a slope to a set distance from one feature line, use that to create a surface and target the surface with a grading from the other feature line.
There are many options in the gradings that you can look into.

[rustee4u]

Thanks for the reply,

Yes the two features lines are roughly parallel at a distance of 7m. I like to create a new feature line at an offset of 10m from the first line and at the same grade as between them.Just to clarify more I have attached the PDF showing  the problem in drawing. The existing grade G shown in the pdf is not constant instead varying. 

Thanks

[jmayo-EE]

You can also select the feature line and go to the ribbon. Make sure the Edit Geometry panel is displayed and select the button for Stepped Offset. Provide the horiszontal offset and the %Grade,Slope,ElvDifferenece or elevation you require.

[troma]

The problem here is "The existing grade G shown in the pdf is not constant".
Say the two feature lines are at the same elevation at one end. Then one goes up and one goes down, then they both do whatever. The desired 10m offset featureline is not found by some known grade or elevation difference that can apply to the whole length. It needs to be at a different grade for every point along the way.

[troma]

I have an idea, but it's quite messy.

Draw a featureline or 3Dpoly from every vertex on the first featureline snapped to perpendicular onto the second featureline. Then do the same from the second back to the first.
Offset the first feature line 10m, convert that to a 2Dpoly. Extend all the perpendicular featurelines or 3Dpolys out to this 10m polyline. Now draw your final featureline by snapping to the endpoints of all the perpendicular featurelines or 3Dpolys.

(I just thought; you could use plain old lines for the perpendicular job too.)

[jmayo-EE]

Yep. Didn't read the first post agian. Doing this manually as you said is the only way I see to extend the existing gradiant.

[fcernst]

This can easily be done with a simple corridor and two generic links, by passing the link slope from the first link to the second link, then extract the corridor feature line.

[troma]

How do you run a corridor down a featureline?

Maybe...
Create alignment from entity.
Project object to profile view.
Trace the featureline in profile view with a profile.

Few steps involved, but probably less work than my method, depending on the number of vertices involved.  Also has the advantage of being dynamic (to the second featureline at least).

[fcernst]

You don't need to. They can all just be Targets.

[rustee4u]

Thanks all for your genuine and prompt responses.Some of them are really good advises and will use in future for sure.

For the current project lengh of the road is quiet big and time is severly less so I took help from other road design software MX to design the grade extend line and then import it in to C3D which works quiet well.

Thanks again

[fcernst]

"...so I took help from other road design software..'

Ouch!....just like running to the arms of another man..

[el.Topo]

hi everyone,

in case you are still interested

there are 2 subassemblies that could do the job (the official way)

check them out

OverlayWidenMatchSlope1

This subassembly overlays one side of an existing road, and adds one or more travel lanes to the edge while matching the existing lane slopes.

& OverlayWidenMatchSlope2

This subassembly overlays an existing uncrowned road, and adds one or more travel lanes to the left and right edges while matching the existing lane slope.

"The elevations of the Left and Right Insert Points on the Existing Surface are determined, and the slope is calculated between the two points"

[Joe-Bouza]

This is what the OverlayWidem Subassembly does. you can set the overlay depth to 0 and only get the widen