Re: [MI-L] How to find the "Centre-of-Gravity" of a Region

Sun, 15 Oct 2006 19:13:32 -0700

Sorry, forgot the page regarding my last email:
 
http://www.geocoderun.com/12.html
 


Phil Waight <[EMAIL PROTECTED]> wrote:
I have a definition of 3 polygon centroid types here (shifted centroid,  geometric centroid, visual centroid):
http://www.spatialprojects.com.au/spatialsql_centroids.htm
 
Some more examples and some rules to determine the best choice of centroid for labelling, including calculation of the principal axis for alignment:
 
http://www.spatialprojects.com.au/spatialsql_smartprops.htm
 
The region geometric properties functions are free-use and available from a button pad:
 
The primary use of the alternative centroids noted in spatialSQL is to find valid alternative points for labelling. As can be seen in the examples the choice of one type only would not produce the best results. All computed values are stored in columns in the target table.
 
There are application areas where the geometric centroid or visual centroid could be of use in their own right. The visual centroid is computed with an output radius of the "largest circle to fit" and thus could be used in an SQL to determine that a chosen polygon and v. centroid satisfy a "minimum distance to neighbour" criteria (habitat?, agriculture?)
 
Regards,
Phil Waight.
_______________________________________ 


Email : [EMAIL PROTECTED]
Web: www.spatialprojects.com.au
Skype: PhilWaight
----- Original Message -----
Sent: Thursday, October 12, 2006 11:22 PM
Subject: [MI-L] How to find the "Centre-of-Gravity" of a Region

HI All,
 
Does anybody know how to find the “Centre-of-Gravity” of a region using MapInfo? The centriod location is based on the ‘Minimum Bounds Rectangle’ approach, so the centriod location is not the centre-of-gravity of the region. Also, the centriod can be moved for presentation purposes etc. This means that the coordinate extractor tool does not work for my purposes.
 
Any help in this matter will be greatly appreciated!!
 
Many thanks,
 
Stephen
 
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