Intersection line with equal distance to polygon sites

[TimLuber]

Hi,

I have a shapefile/polygon of a peninsula and I want to produce a line that intersects the polygon in the middle of the peninsula, therefore always has the same distance to the shore left and right even if the form of the peninsula changes (slims or gets wider).

Is there any way to do that ? I know if I would have the line I could produce the polygon with the buffering tool, but is there an inverse way ?

Thanks

Tim

[JustinOdell]

I was curious on this myself, and have done some research.

Apparently some people have made use of the 'Collapse dual lines to centreline' tool in ArcInfo.  However through experimenting with this, I've had some problems generating anything that looks remotely like a centreline!

The only other option I can think of is to draw lines across the peninsula, joining points, and then draw a line, snapping to the midpoint of each of those lines.  Having said that, this would not be practical for a peninsula containing several vertices...

I don't know how else to approach this, and would be interested to find out a solution on this.  Surely it's a relatively simple function which does not require scripting...

See these threads for some insight:
http://forums.arcgis.com/threads/13372-Create-Centerline?highlight=centerline
http://forums.arcgis.com/threads/21461-Create-centreline-from-a-polygon?highlight=centerline
http://forums.arcgis.com/threads/20262-Odd-polygon-centerlines?highlight=centerline
http://forums.arcgis.com/threads/15690-Polygon-Centre-Line?highlight=centerline
http://forums.arcgis.com/threads/11744-Polygon-to-centerline?highlight=centerline

There seem to be a few threads created regarding centreline creation without valid responses.

Any advice from an ESRI technician would be great!

[TimLuber]

Hi,

I tackled the problem with the Geowizard extension, which is available at:

http://www.ian-ko.com/

You can download it and dont have to register it, even though you can't use all tools you can use the centerline tool or polygons and that does the trick. It takes a while playing around with the tool but it is worth it.

Sometime when the polygon varies to much in size it does not quite work so well but if you split up your polygons in several and apply the tool to all and then put a new shapefile (line) over the individual created centerlines it does a good job.

Hope that helps.

Thanks for the links and post.  😉

[DarrenWiens2]

I've been making approximate centreline files of linear polygon feature classes using:
1.) Polygon to Raster
2.) Thin
3.) Raster to Polyline
Since penisulas are just fat linear polygons, I thought I'd give it a try. I used Florida, but it's a little too stubby to work really nicely. If you have Spatial Analyst and just want a quick way to make a centreline, this works all right.