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How to ... clip a polygon by a line

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#1
Kristin

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Is there any way to use a line featureclass to clip a polygon? I am working with ArcMap 9.3.

I am looking at shoreline data to estimate area of certain habitat types (mudflats, estuaries, and intertidal zones). The habitat data I have is a line shapefile of the shoreline. I would like to extend a buffer to capture a set distance away from shoreline. However I would like to clip the resulting buffer to the low-tide mark, and of course only include the ocean side of the shoreline in the buffer.

Any suggestions are much appreciated!

Kristin

#2
eli

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do you have access to the topology toolbar? I would use the construct features tool to do that. it won't make a new shapefile, but update the existing one with the line that you select. you can then delete the portion of the poly that you don't need.

http://webhelp.esri...._topology_tools

#3
Kristin

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Hey eli, thanks for the tip. I haven't used topology before and it seems like a great feature. Unfortunately access is blocked for ArcView and I only have access to "'Topology Edit" tool, no "Construct Features".

I think I might be able to do something similar to "split" my polygon by my line however that would still leave me with having to delete the unwanted side, which is more editing than I am hoping for; I'm thinking there must be a simpler solution to make this work

#4
Dennis McClendon

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I'm in over my head, but why not just add two points way off on one edge or the other to make the line into a closed polygon and then clip the usual way?
Dennis McClendon, Chicago CartoGraphics
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#5
Kristin

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I'm in over my head, but why not just add two points way off on one edge or the other to make the line into a closed polygon and then clip the usual way?


You might be over your head, but I am definitely over-thinking this!

I'm not sure how I can convert my line into a closed polygon... I know there is a tool to convert lines to polygons, however I don't have the ArcInfo license needed.

This thread - http://forums.esri.c...p...87&t=193449 - suggests ET Geowizards. Anyone used this and can review? Licensing for the full version is still pricey. Going to give the trial a try, hope that is works for this!

#6
eli

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Yep, I recommend ET Geowizards for the people that don't have ArcInfo licences. You could also try QGIS, it has a lines to polygon tool.

#7
Dennis McClendon

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Perhaps a diagram to explain:

You want to clip the tan polygons using the blue coastline. I can't check right now, but can't you launch an edit session and just add (or move) a couple of points to make the line a closed line that goes safely west of the polygons, then do a clip in the usual way?

Posted Image
Dennis McClendon, Chicago CartoGraphics
chicagocarto.com

#8
Laura Miles

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Close the polygon as Dennis suggests, then use the "Feature to Polygon" tool, then you can clip away!




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