topic Re: How to Convert Polyline to Polygone in AutoCAD Forum

How to Convert Polyline to Polygone

Alas_1234 — Sat, 06 May 2023 19:05:21 GMT

I have road surface in Autocad. I tried to create polygon area to be used in ArcGis in polygon shape. (I tried convert shape to polygon in Arcgis but I have not satisfy.)

First I tried to join all lines but it takes too much time. Is there any easier method to provide solution to create polygon in Autocad?

I uploaded my file as an attachment. Thanks.

Re: How to Convert Polyline to Polygone

Kent1Cooper — Sat, 06 May 2023 19:31:59 GMT

PEDIT command, Multiple option, select, Join option, give it a fuzz factor. In your example drawing, a fuzz factor of zero reduced the number of Polylines from 81 to 23 [slightly better than JOIN's 27], a fuzz factor of from 1 to 10 reduced them to 15. You can experiment with going further, but to get one you will at least need to FLATTEN them all to the same elevation -- Polylines at different elevations can't be joined.

Re: How to Convert Polyline to Polygone

Alas_1234 — Sat, 06 May 2023 20:20:14 GMT

Thank you for your reply.

When I use flatten command all polyline were erased. I could not figure out the reason.

If there is another method to create polygon I would like to hear. Thanks

Re: How to Convert Polyline to Polygone

Michiel.Valcke — Sat, 06 May 2023 20:40:24 GMT

You should use AutoCAD MAP 3D to prepare CAD geometry for conversion to GIS. AutoCAD MAP 3D has several functions to do this.

The vanilla AutoCAD POLYGON command just creates a closed polyline.

MPOLYGON (can make multipolygon by following the options)

MAPPOLYLINETOPOLYGON (when selecting a group of polylines will create a multipolygon)

MAPEXPORT (direct export to shp or other GIS format, which has the option to treat closed polylines as a polygon)

If you have a full AutoCAD (not LT) then AutoCAD MAP 3D is a part of your licence. It is an AutoCAD toolset, so you will have to install it separately, but it contains all functionalities that vanilla AutoCAD has, and then adds a whole lot of functionalities specifically to work with / for GIS

Re: How to Convert Polyline to Polygone

Michiel.Valcke — Sat, 06 May 2023 21:05:53 GMT

after looking at your shape, you will need to do a lot more cleanup to be able to convert this to a useable closed shape.

It must be a closed polyline, so you cannot have segments with different elevations or overlapping segments.

You cannot have intersecting segments, in other words your segments cannot cross themselves. If found a few already, but I imagine your shape has hundreds of them.

It might be easier to divide it up into a lot of smaller segments, which individually will be easier to conform to the above rules. Once you have then checked and converted each segment you can join them again in one multipolygon shape.

Re: How to Convert Polyline to Polygone

Kent1Cooper — Sat, 06 May 2023 22:44:34 GMT

@Alas_1234 wrote:

.... When I use flatten command all polyline were erased. .... If there is another method ....

Since they're all Polylines, you could select them all, and give them all zero elevation in Properties, collectively. But that won't fix things like overlaps and self-intersections pointed out by others.

Re: How to Convert Polyline to Polygone

WeTanks — Sun, 07 May 2023 02:20:02 GMT

Maybe it will suit you better.

https://www.autodesk.com/products/autocad/overview?term=1-YEAR&tab=subscription#:~:text=Tailored%20to%20work%20for%20your%20industry

Re: How to Convert Polyline to Polygone

AVCPlugins — Sun, 07 May 2023 03:05:20 GMT

Try the OSL command from my AVC Outside Loop plugin. This command will create a closed polyline from any garbage. Moreover, it can convert unsuitable objects into polylines and can search for the largest outer contour among all line intersections. You may also find the AVC Flat plugin useful, which projects any objects onto the XY plane without creating a block.

Re: How to Convert Polyline to Polygone

Alas_1234 — Sun, 07 May 2023 09:17:09 GMT

Thank you for your kind advice but I could not figure out how I use this tool.

Re: How to Convert Polyline to Polygone

AVCPlugins — Sun, 07 May 2023 15:28:21 GMT

I looked at your file. There are very low quality contours. The right end of the road is not closed at all. Some of the polylines are raised in Z up from the XY plane. There are many open segments and a lot of lines overlapping one on top of the other. As a result, neither _OVERKILL nor AVC Outside Loop can handle it, even if the accuracy is reduced to 1mm. But after OSL processing (when setting the tolerance to 1mm), there are not many glitches left at all. Unfortunately, a little editing is still required, but this is no longer a long job. I will try to fix the OSL work for the next version so that it handles such contours without errors. Thanks for the example.

Re: How to Convert Polyline to Polygone

RobDraw — Sun, 07 May 2023 22:50:24 GMT

"How to Convert Polyline to Polygone"

Sometimes typos are funny.