Need to create a shape with a hole in it

[CivilDavid]

I have closed polyline within another closed polyline.  I need to create a shape and I need a hole in it.  See attached pdf for example.  Ignore the dashed and solid grey lines, not sure what those are.

When I select the two polylines, and select treat closed polylines **** polygons, then I export as shapes, I just get two solid shapes, one on top of the other.  Any help would be greatly appreciated.  Thanks in advance.

[Jeff_M]

Convert the plines to regions, then Subtract the smaller one from the larger one.

Command: REGION

Select objects: 1 found

Select objects: 1 found, 2 total

Select objects:
2 loops extracted.


2 Regions created.

Command:
Command: _subtract Select solids, surfaces, and regions to subtract from ..

Select objects: 1 found

Select objects:  Select solids, surfaces, and regions to subtract ..
Select objects: 1 found

Select objects:

Command:

[Alfred.NESWADBA · Accepted solution]

Hi,

as long as that are only few POLYLINEs you can start the command MPOLYGON. With this command and the option to choose elements you can select the POLYLINEs and will get a new object containing one outline and as many islands as you selected. This object can then be exported to SHPs.

If you have many objects, you would have to build a map-topology and then export the topology with MAPEXPORT.

HTH, - alfred -

[CivilDavid]

then how do I export that region as a shape?

[CivilDavid]

thanks, this worked great.  I've never used the mpolygon command, I always export shapes through MAP, but now I can create the mpolygons the way I like, then export as polygons.  Thanks!

[antoniovinci]

> then how do I export that region as a shape?

You can't.

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About creating "holed" shapes with MPOLYGON, that's good if you start from scratch.

But if you wanna hole an existing shape having Object_Data (GIS attributes), MPOLYGON will destroy them.

In this case, the solution will be the second one from Alfred: _MAPEXPORT of the topology.

[neilyj666]

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@Alfred.NESWADBA wrote:

Hi,

as long as that are only few POLYLINEs you can start the command MPOLYGON. With this command and the option to choose elements you can select the POLYLINEs and will get a new object containing one outline and as many islands as you selected. This object can then be exported to SHPs.

If you have many objects, you would have to build a map-topology and then export the topology with MAPEXPORT.

HTH, - alfred -

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How do I go about building a map topololgy??

[Alfred.NESWADBA]

Hi,

>> How do I go about building a map topololgy??

In one word? _MAPTOPOCREATE,

In one page? look >>>here<<<

BUT don't start the command and think "that's it"!

Try to get training(s) or at least do research around GIS-Topologies and Map3D-Topologies (e.g. >>>here<<<), becaue all data-preparation (MAPCLEAN), the work with object-data, with connected database-tables/views/queries ..and..and..and makes GIS what GIS is and has to be learned.

Have a nice day in Google 😉 , - alfred -

[neilyj666]

Alfred - thanks for the info and links.

I don't use the GIS functionality day in day out but am sure it could speed up certain tasks for me - I just need to find time to learn about it...!!!!!

[antoniovinci]

Neilyj,

I really can't imagine my work in Map/Civil environment without topologies: with them, you make buffers, overlays, create closed polylines, and so on.

Topology is the foundation of every serious GIS job, because it guarantees you only clean and consistent data.

Unfortunately, as said by herr Alfred, to achieve the condition to get a correct topology, you must previously struggle with the _MAPCLEAN command: that's very boring and frustrating, expecially if you have to manage DWGs from other people...

[AllenJessup]

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@neilyj666 wrote:

I don't use the GIS functionality day in day out but am sure it could speed up certain tasks for me - I just need to find time to learn about it...!!!!!

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One of the best classes I took was how to use Map in Civil design work!

Allen

[AllenJessup]

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@antoniovinci wrote:

Topology is the foundation of every serious GIS job, because it guarantees you only clean and consistent data.

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That makes great sense for GIS jobs. It doesn't work as well when doing Survey and Civil Engineering. Usually I can't let the program decide how to clean up the errors because it doesn't know the rules that govern in Survey and Design. If I have a drawing from an outside source I can us Mapclean to MARK the problem areas.

Allen

[Joe-Bouza]

I don't know map topologies per se, but maybe what I do is that. I draw my polygons >> mapexport each to its own sdf file>> connect the FDO >> do an overlay and choose subtract one from the other then save the result to its own sdf file = shape with a hole in it.