5 Replies Latest reply on Oct 17, 2012 1:41 PM by navaneet

# Calculate centerline length from polygon

How to convert polygon to centerline to calculate its length?
• ###### 1. Re: Calculate centerline length from polygon
I presume that you are not after the length of a polygon's bounday but the length of a medial line after its construction from a polygon?

Oracle 11gR2 does not have such a capability. It might do in 12c but no one knows what is planned for that release, spatially.

I have been contacted a number of times about implementing a medial axis algorithm for my Spatial Companion 4 Oracle (SC4O) free software. It can be done as this example from wikipedia shows:

https://commons.wikimedia.org/wiki/File:Medial_axis_example_2d.svg

But I am not prepared to implement such an algorithm without 1) real data and, 2) some sort of incentive.

regards
Simon
• ###### 2. Re: Calculate centerline length from polygon
Hi Navaneet,

As Simon mentioned, there is no native function in Oracle Spatial to generate a centreline for a polygon and I am not aware of any existing implementation that will run in Oracle. There are various implementations in commercial software applications, but I guess I can't list them here.

If you are interested in reading more about generating polygon centrelines, there is an excellent blog series on the Smathermather's blog:
http://smathermather.wordpress.com/2011/09/16/what-is-the-center-line-of-a-polygon-or-how-to-change-labeling-in-geoserver/
http://smathermather.wordpress.com/2011/09/26/what-is-the-center-line-of-a-complex-polygon-cont/
http://smathermather.wordpress.com/2011/10/08/what-is-the-center-line-of-a-complex-polygon-cont-2/
http://smathermather.wordpress.com/2011/10/18/what-is-the-center-line-of-a-complex-polygon-cont-3/
http://smathermather.wordpress.com/2012/01/14/what-is-the-center-line-of-a-complex-polygon-cont-again/
http://smathermather.wordpress.com/2012/01/17/what-is-the-center-line-of-a-complex-polygon-new-approach/
http://smathermather.wordpress.com/2012/08/02/what-is-the-center-line-of-a-complex-polygon-routing-as-the-solution/
http://smathermather.wordpress.com/2012/08/09/what-is-the-center-line-of-a-complex-polygon-routing-stream-and-rivers/
http://smathermather.wordpress.com/2012/08/10/what-is-the-center-line-of-a-complex-polygon-routing-stream-and-rivers-part-two/

Regards,
John
• ###### 3. Re: Calculate centerline length from polygon
John

Nice example. Identification of text angle for parcel boundaries is excellent.

Best
Navaneet
• ###### 4. Re: Calculate centerline length from polygon
Simon,

Yes. I was interested in the length of the medial line.

I searched all the oracle functions and your site and after exhaustion I put down this question.

Since it is simple sleeve around gas pipes with constant diameter, I devised a workaround to resolve the current problem. But to determine medial line on complex polygon as mentioned in John's example will require more involvement. I also used Safe Software 'CenterLineReplacer' with success.

It is better we have this as of part of future oracle functions.

Best
Navaneet

Edited by: navaneet on Oct 16, 2012 4:21 PM
• ###### 5. Re: Calculate centerline length from polygon
Successfully used the Safe Software 'CenterLineReplacer'. Achieved the desired results using classic mode parameter.

Edited by: navaneet on Oct 17, 2012 9:41 AM