[postgis-users] polygon with equally spaced points from an existing polygon

[Luis Tavares]

Hi all,

Thanks for your suggestions,

What I really need is a polygon that have exactly the same geometric center (centroid) of the original polygon. I don´t know If generalization algorithms (like st_simplify) have this property. Same for st_segmentize. I need to make some tests first.

strk,
The use case is precisely calculating the polygon´s centroid by averaging the coordinates of all the points of the polygon. In order to perform this I think I need to have equally spaced points. Note that I´m working on the ellipsoid so st_centroid no good to me...and I don´t want to project coordinates.  

Thanks


Luis Tavares

________________________________
 From: Sandro Santilli <strk at keybit.net>
To: Luis Tavares <lmikegeo at yahoo.com>; PostGIS Users Discussion <postgis-users at lists.osgeo.org> 
Sent: Tuesday, March 12, 2013 8:50 AM
Subject: Re: [postgis-users] polygon with equally spaced points from an existing polygon
 
On Mon, Mar 11, 2013 at 09:22:09PM -0700, Luis Tavares wrote:

> How do I create a polygon with equally spaced points from an existing polygon?

Looks like a two steps process:

1) drop vertices that are too close (st_simplify may help)
2) add vertices where missing (st_simplify)

> I know that more the curvature or concavity changes sign more points are needed. So one solution would be to calculate the minimum of all distances between two consecutive points in the original polygon and use that distance to build my polygon with equally spaced points. Is this correct? If so, How do I proceed from here? Any ready made solution?

Calculating the minimum of all distances between two consecutive
points could be a useful standalone function. Don't you also need
minimum distance between any two points ? I'm curious about the
use case for the "consecutive only" approach.

--strk;
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