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I have 20,000 polylines in a .gdb that represent about 5,000 building footprints. Some of the building footprints have pretty substantial gaps (image below). I would like to snap the polylines closed into polygons so that I can extrude the buildings... Is there an app for that?

building footprints

I have access to ArcView 9.3, but that hasn't been very helpful. I am hoping that there is something in the opensource community with a "Clean" or somesuch functionality.

Thanks in advance for any thoughts!

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I was reading this hopeful but my solution would require ArcGIS Desktop ArcEditor License. Is there any chance of you getting access to this? – CDBrown Apr 20 '11 at 5:52
@CDBrown - No ArcEditor for me... At least not for this project. – BrianPeasley Apr 20 '11 at 16:30
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@Sean - Why did you remove the "qGIS" and "OpenSource" tags from my question? The folks who read those questions are the ones who may have the answer I need. – BrianPeasley Apr 20 '11 at 16:33
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I'm ok with a moderator adding them back but your question was specific to QGIS. The questions asks for ArcView or Open Source so it's not specific to QGIS and adding a tag for every open source app would be a bit much. I've added open-source and and ArcView but it's not really a question specific to either. I'll leave it to more experienced users to correct. – Sean Apr 20 '11 at 17:47
@Sean - Gee shucks, thanks for allowing me to have the "OpenSource" tag attached to my question – BrianPeasley Apr 20 '11 at 18:14
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3 Answers

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In GRASS GIS, you can use v.edit's snap tool.

snap: Snap vector features in given threshold

There are options to snap to a node or a vertex.

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Can you please elaborate? Would this snap to closest vertex within the given distance? I am interested because ArcGIS has a similar snapping functionality but it would choose the closest vertex. (Not necessarily the vertex that it should be snapped to) The lines here might need to be extended in the direction of the line. Also seems like there might be issues in some of the corners where two lines need to be extended until they meet. Can GRASS GIS do this? – Jakub Apr 21 '11 at 1:33
This seems like the right path... It is with an odd mixture of resignation and anticipation that I download my first copy of GRASS tonight. Thanks for pointing me in the right direction – BrianPeasley Apr 21 '11 at 4:17
up vote 1 down vote

I tried a few tricks in CAD with no luck. I think - although I'm not certain - that ET Geo-Tools, or ET-Geowizard will have something with this functionality. It's not that expensive, and actually does a lot of different things (terrific add-on!!!!). See this link:

ET GeoWizard

Also .... There is an ESRI forum discussing this very issue. The same suggestion was made there (the GeoTools route). The methodolgy for the conversion can be found within this thread. Just read through the discussions and you'll see what I'm referring to (the workflow is outlined near the end).

Hope this helps

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Thanks Dano - The ET site claims that "Polyline to Polygon" is a free function of the GeoWizard add-on... For that I'll take this as a valid answer, however I'm not going to try it out anytime soon. This is not a paid gig for me (read "I'm in no hurry") and it is high time that I dug into an Open Source solution. I'm gonna try out the GRASS solution as per Maning's suggestion above. – BrianPeasley Apr 21 '11 at 4:01
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I think you should be able to do this with ArcView 9.3 or 10.0.

First use Extend and Trim to try and close as many of the building footprints as possible.

Then use the Export To CAD tool to convert the feature class into a DXF file.

Add the DXF file to your map and you should see that it has a polygon dataset within it.

You can then export those CAD polygons to a shapefile or feature class of polygons.

Going out to and back from the DXF file in this way accomplishes the Polyline to Polygon conversion.

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