Max diameter of non circular object

[Ed]

Hi all,

This has probably been asked before but not sure of the best way to do it.

I have a cellular dominance map of each cells unique coverage area. I want to run a query on the max diameter of the shape file to give a very general 'Max serving range'.

So, in the enclosed image it would be the length of the red line.

My old school maths is not coming back to me, if I got the perimeter of the shape, could I just extract the generic diameter from this. I know the objects aren't neccessarily circular, but this just has to be somewhat accurate!

thanks in advance.

Ed

[Thomas Bacon]

Hi Ed,

 

You could do this with a perfect circle (or an oblong circle as long as the stretch was perfectly along the x or y axis) by using the MBR function to get the bounding rectangle and using the longest of width or height as the result. Unfortunately, with irregular polygons such as the one’s you have, I’m pretty sure the only way is to get the distance of each node of the polygon to all of the others and determine the longest length from the results. A fairly simple MapBasic script could do this if you’re happy to do some coding.

 

Regards,

 

Tom Bacon

GIS Engineer, Mouchel

T 01444 472380 │ E thomas...@mouchel.com │ W www.mouchel.com

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[Lars I. Nielsen]

Hi Ed,

 

I suggest doing it this way:

 

1.       Convert your outer perimeter(s) for each distinct coverage area into a table of points.

2.       Build a table of distances between each set of 2 points.

3.       Find the maximum distance, yielding the two points furthest from each other. This is your "maximum range" represented by the red line.

 

I think there are available tools for 1 and 2.

 

Kind regards / Med venlig hilsen
Lars I. Nielsen
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