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Thread: Error creating Spiral to Spiral

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    Default Error creating Spiral to Spiral

    I am a land surveyor, tasked with laying out a road centerline that was designed in the early 20th century. The alignment is a series of tangent, spiral, curve, spiral, tangent, ect. There is one point where the series is broken and the plan calls for a spiral into a curve with and arc length of 0.00, then a spiral out. I cheated here and gave the arc length a value of 0.01 feet. Now, given the extreme difficulty I encountered attempting to create this alignment in civil 3d, I used a third party program to create a land XML file of the alignment. Everything looks good with my xml file, but when I import the alignments into civil 3d, it takes the arc length of 0.01 feet and somehow curves it back on it's self. This results in erroneous station and offset information when labeling or creating points. As far as I can tell, it's a flaw in the programing, has anyone come across this before?

    I have attached my drawing, the problem can be seen on the CL2 Alignment @ STA: 497+61.23

    On a sidebar, I can't believe how difficult it is to work with spiral curves in civil 3d. I attempted many ways of creating the series of spiral curve spiral from the tangents and each time I could only get one curve. When I tried to connect to the next tangent, the program would say the elements weren't tangent, even though they were. I drew all my tangent lines and created each curve as a floating spiral curve spiral, exploded them and saved the main curve. I didn't have any luck with this method either, after connecting one curve with it's tangents using spirals, and attempting to connect the next curve with a spiral, the program would tell me it was not tangent. Bull honkey, the lines and curves were created by the alignment and were definitely tangent. I ended up using Carlson Survey to create my alignment, it has a beautiful centerline editor. It was as simple as typing in the information on the plans and, boom, I had my centerline. Why doesn't civil 3d have something like this, the alignment editing tools it does have are lacking, especially when spiral curves are involved or you have hard data that needs to be held. That's my $0.02
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    Administrator rkmcswain's Avatar
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    Default Re: Error creating Spiral to Spiral

    Quote Originally Posted by justinpickens77701535 View Post
    Why doesn't civil 3d have something like this
    The real answer? Because they don't have to.

    You might go here to make your voice known. Read this first before posting.
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    Default Re: Error creating Spiral to Spiral

    Thank you for your reply, I read the links you provided but they didn't answer my question.

    Why does civil 3d think that the elements in my alignment are not tangent to each other?
    Is it possible to create an alignment with a spiral to spiral?
    Is there an "alignment calculator" of some sort in civil 3d or do you have to use the graphic tools?

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    Default Re: Error creating Spiral to Spiral

    Well, those links won't answer your questions, but they will give you a chance to suggest ideas and improvements to the c3d developers that directly address you needs.

    Re your first question, one possibility is that the coordinate values are so high that rounding errors are creeping in. I see that often enough with basic geometry, example creating a circle using TTR with linework on state plane coordinates, and it seems to be most common with tangents.

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    Default Re: Error creating Spiral to Spiral

    Well it looks like I'm talking to a brick wall here, or speaking Greek...

    If anyone would care to look at my drawing and offer suggestions on how to fix the spiral to spiral error I'm experiencing, it would be greatly appreciated.

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    Default Re: Error creating Spiral to Spiral

    I could certainly be wrong, but my perception is that there are many more C3D professionals to be found on the Autodesk Civil 3D forum.
    You might want to consider posting there for a larger audience.
    R.K. McSwain | CAD Panacea |

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    Default Re: Error creating Spiral to Spiral

    HI
    I just seen your problem and have recently gone through something similar. First let me say I AM NOT a expert on spirals, but here was some of my problems. There is a tabulation editor, upon looking at by a suggestion from a experienced operator I found I had 2 zero or near zero length curves caused by graphically editing. that threw the alignment into a tizzy. second you may need to change your perspective a little (it helped me) Civil3D is a design program look at designing a spiral with the given parameters instead of plotting it like normal. The next best thing I found that works for me is to calculate all the pi's draw a pl from pi to pi (important here only pi to pi) then make an alignment from the pl then edit in each curve one at a time worked much better for me.

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