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Centerline from Buffer

18 REPLIES 18
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Message 1 of 19
Vasily_BC
1383 Views, 18 Replies

Centerline from Buffer

Hi,

 

I know that it probably old story, however I didn't find an answer.

Is there way to create centerline from buffer or polygon in Civil 3D?

There is should be some easy method to do it.

By now the only proper way is to explode object, delete lines that are smaller than minimum and do offset for merged border.

 

Any ideas?

 

Thanks

18 REPLIES 18
Message 2 of 19
BrianHailey
in reply to: Vasily_BC

I honestly don't know what you are trying to accomplish. Perhaps you could provide a drawing or an image showing what it is you are trying to do.

 

When I think of buffer, I think of an area around something. Is that what you mean by a buffer?

Brian J. Hailey, P.E.



GEI Consultants
My Civil 3D Blog

Message 3 of 19
tcorey
in reply to: Vasily_BC

I'm sure youre license is Civil 3D, but your question is a Map question, right? Perhaps posting in the AutoCAD Map group would yield better results.



Tim Corey
MicroCAD Training and Consulting, Inc.
Redding, CA
Autodesk Gold Reseller

New knowledge is the most valuable commodity on earth. -- Kurt Vonnegut
Message 4 of 19
Vasily_BC
in reply to: Vasily_BC

The thing is that I have shapefile of 60m corridor along transmission line 120 km long. I need to extract centerline from it. Of course I can do it manually, but it's 120km. I've tried to explode shapefile and delete short lines that was on rounded corners and then extend the rest. However, I realize that even this could take hours and also it's not a beautiful way to do it. I know it could be done in ArcGIS by Collapse Dual Lines To Centerline, but I believe it could be done in AutoCAD.

I've also tried to create best fit alignment. It freeze my computer every time.

I'll upload picture tomorrow morning.

ps. I think this case could be applicable both to Civil 3D and Map 3D because everyone works with shapefiles.

 

Thanks!

Message 5 of 19
sboon
in reply to: tcorey

I'm taking a bit of a guess as to what the OP is trying to do but - given a polygon like this one how would you accurately recreate the original centerline?  Some parts of it are easy, but not all.

 

Clipboard01.png

 

Steve
Expert Elite Alumnus
Message 6 of 19
neilyj666
in reply to: sboon

That's my understanding of the question as well

 

Not overly familiar with shapefiles but If the shapefile was exploded into CAD line primitives, would using JOIN not create a polyline that could be offset 60m?

neilyj (No connection with Autodesk other than using the products in the real world)
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Message 7 of 19
Vasily_BC
in reply to: sboon

Hi,

 

You understand it right. Here couple screenshots of shapefile.

Shapefile has 3638 vertexes! However, most of them are not important because was made by feature buffer command (my guess). Also explode method was just a try to get centerline. I can use offset, but as a result will get polyline with extra 1800 vertexes!

1.JPG

2.JPG

Message 8 of 19
Alfred.NESWADBA
in reply to: Vasily_BC

Hi,

 

>> The thing is that I have shapefile of 60m corridor along transmission line 120 km long.

>> I need to extract centerline from it

I would:

  • run _MAPIMPORT to get it into AutoCAD as Polyline.
  • next run command _OFFSET with the value of 30 (half of the corridor width) to the inside
  • if there are now double objects then you can use _MAPCLEAN to delete double and maybe to join elements together.

Does that help?

 

- alfred -

------------------------------------------------------------------------------------
Alfred NESWADBA
Ingenieur Studio HOLLAUS ... www.hollaus.at ... blog.hollaus.at ... CDay 2024
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(not an Autodesk consultant)
Message 9 of 19
Vasily_BC
in reply to: Alfred.NESWADBA

It would work but it will take hours cause offset works only with ONE object. However, it is only way so far.

It will be easer to query lines that are 10m and less for example, delete them, do offset for the rest and do extend for missing parts.

I believe that there is should be some proper and beautiful way how to do it.

Message 10 of 19
Alfred.NESWADBA
in reply to: Vasily_BC

Hi,

 

>> It would work but it will take hours cause offset works only with ONE object

I thought you have ONE corridor? Then you would only have one _OFFSET-command.

 

BTW: the most easiest way would be to get the source of the buffer, at least look to backups because there was an element from which the buffer were created.

 

- alfred -

------------------------------------------------------------------------------------
Alfred NESWADBA
Ingenieur Studio HOLLAUS ... www.hollaus.at ... blog.hollaus.at ... CDay 2024
------------------------------------------------------------------------------------
(not an Autodesk consultant)
Message 11 of 19
jmayo-EE
in reply to: Vasily_BC

The Join and Weed Feature Line command or Mapclean can be used to get rid of most of those verticies and make a single pline. If you do this the offsetting and other operationsshould perform much better.

John Mayo

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Message 12 of 19
jmayo-EE
in reply to: jmayo-EE

If these operations take too long or dog the machine down, then perform the operations on small portions of the buffer. Working with segements of the data will speed you up and you can join the segements together to finish.

John Mayo

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Message 13 of 19
Vasily_BC
in reply to: jmayo-EE

Another method maybe.

1. Create a surface based on sides of ROW.

2. Create contour lines.

3. Extract contour lines.

4. Find proper one.

 

It could be very good technique, but triangulated surface is nor ideal and needs time for correction.

3.JPG

Message 14 of 19
BrianHailey
in reply to: Vasily_BC

Can you share the file? I have some ideas that I want to try on it.

Brian J. Hailey, P.E.



GEI Consultants
My Civil 3D Blog

Message 15 of 19
Vasily_BC
in reply to: jmayo-EE

Sure.

Message 16 of 19
antoniovinci
in reply to: Vasily_BC

I concur with Alfred's solution: check this out (more exactly, the animation of 2012/09/17 20:30 post).

Message 17 of 19
Vasily_BC
in reply to: antoniovinci

The thing is that offset to within doesn't work. Maybe because AutoCAD can't find its center?

Message 18 of 19
BrianHailey
in reply to: Vasily_BC

Here's the problem, you have 15 gazillion verticies (yes, I counted) on that buffer because of the way it was created (i.e. no curves). When doing anything with that, it's going to bomb out on you so get rid of all the little segments.

 

HERE is my solution.

Brian J. Hailey, P.E.



GEI Consultants
My Civil 3D Blog

Message 19 of 19
tcorey
in reply to: BrianHailey

Hello Brian,

 

You solution works for parallel offsets, but what happens when the two sides of your figure are not parallel? How do you ensure your new polyline is centered between points at a particular station?

 

Tim

 

 

 

 

 

 

 

 



Tim Corey
MicroCAD Training and Consulting, Inc.
Redding, CA
Autodesk Gold Reseller

New knowledge is the most valuable commodity on earth. -- Kurt Vonnegut

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