# [Met_help] [rt.rap.ucar.edu #52815] History for how the centroid calculated in the mode step?

John Halley Gotway via RT met_help at ucar.edu
Thu Jan 19 09:29:10 MST 2012

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Initial Request
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Dear Sir:

The defination of isolated objects is not the same as the convex hull of the objects, is that right? I just want to make sure the centroid is calculated from the objects, not from the convex hull.

Thanks!

Kefeng

2012-01-18

kefeng

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Complete Ticket History
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Subject: Re: [rt.rap.ucar.edu #52815] how the centroid calculated in the mode step?
From: John Halley Gotway
Time: Thu Jan 19 08:55:14 2012

Kefeng,

The convex hull is *NOT* used to calculate the centroid of the object.
Instead, the centroid is computed like a center of mass using the 1st
order moments of the object.  More details on the
mathematics employed can be found on the MET website:
http://www.dtcenter.org/met/users/docs/overview.php

Please take a look at the write-up titled "Moments, Centroid, and Axis
Angles".

Hope that helps clarify.

Thanks,

John Halley Gotway
met_help at ucar.edu

On 01/18/2012 09:51 PM, kefeng via RT wrote:
>
> Wed Jan 18 21:51:12 2012: Request 52815 was acted upon.
> Transaction: Ticket created by kefeng at ou.edu
>         Queue: met_help
>       Subject: how the centroid calculated in the mode step?
>         Owner: Nobody
>    Requestors: kefeng at ou.edu
>        Status: new
>   Ticket<URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=52815>
>
>
> Dear Sir:
>
>       The defination of isolated objects is not the same as the
convex hull of the objects, is that right? I just want to make sure
the centroid is calculated from the objects, not from the convex hull.
>
>       Thanks!
>
> Kefeng
>
> 2012-01-18
>
>
>
> kefeng

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Subject: how the centroid calculated in the mode step?
From: kefeng
Time: Thu Jan 19 09:28:19 2012

Thanks! John.

It helps!

kefeng

Halley Gotway via RT

the mode step?

Kefeng,
The convex hull is *NOT* used to
calculate the centroid of the object.  Instead, the centroid is
computed like a center of mass using the 1st order moments of the
object.  More details on the
mathematics employed can be found on
the MET website:
http://www.dtcenter.org/met/users/docs/overview.php
look at the write-up titled "Moments, Centroid, and Axis Angles".
Hope that helps clarify.
Thanks,
John Halley Gotway
met_help at ucar.edu
On 01/18/2012 09:51 PM, kefeng via RT wrote:
>
>
Wed Jan 18 21:51:12 2012: Request 52815 was acted upon.
>
Transaction: Ticket created by kefeng at ou.edu
>         Queue:
met_help
>       Subject: how the centroid calculated in the mode
step?
>         Owner: Nobody
>    Requestors: kefeng at ou.edu
>
Status: new
>   Ticket<URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=52815>
>
>
> Dear
Sir:
>
>       The defination of isolated objects is not the same as
the convex hull of the objects, is that right? I just want to make
sure the centroid is calculated from the objects, not from the convex
hull.
>
>       Thanks!
>
> Kefeng
>
> 2012-01-18
>
>
>
>
kefeng

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