[Met_help] [rt.rap.ucar.edu #79572] History for MODE attribute question

[John Halley Gotway via RT]

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  Initial Request
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I see in the MODE configuration file the attribute weight category
*int_area_ratio*. The User's Guide does not give an adequate explanation of
this attribute: "the intersection divided by the minimum object area
ratio". What does that mean?  Should this actually be "the ratio of the
area of intersection to the union area"? Please clarify. Thanks.
ratio
Jeff Duda

-- 
Jeff Duda
Post-doctoral research fellow
University of Oklahoma School of Meteorology


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  Complete Ticket History
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Subject: MODE attribute question
From: John Halley Gotway
Time: Fri Feb 17 15:13:38 2017

Jeff,

Let's say that F is the forecast object area, O is the observation
object
area, and FintO is the area of their intersection, then
  int_area_ratio = FintO / min(F,O)

You can see this on line 2505 of this source code file:
   met-5.2/src/libcode/vx_shapedata/engine.cc

   2505    attribute   = (p.intersection_area)/(min(p.Obs->area,
p.Fcst->area));

This measure answers the question, how much is one object consumed by
the
other?

We did recognize that intersection/union would be a more intuitive
measure,
but we found it to be too "strict" when there is a discrepancy in
object
areas.  If the forecast object is fully contained within the
observation
object but is 1/4 the size, int_area_ratio = 1, but intersection
divided by
union = 0.25.

Defining the denominator as the minimum of the two areas minimizes the
impact of differences in object areas... which is measured directly by
the
area ratio pair attribute anyway.

Hope that helps clarify.

Thanks,
John



On Fri, Feb 17, 2017 at 2:57 PM, Jeff Duda via RT <met_help at ucar.edu>
wrote:

>
> Fri Feb 17 14:57:41 2017: Request 79572 was acted upon.
> Transaction: Ticket created by jeffduda319 at gmail.com
>        Queue: met_help
>      Subject: MODE attribute question
>        Owner: Nobody
>   Requestors: jeffduda319 at gmail.com
>       Status: new
>  Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=79572 >
>
>
> I see in the MODE configuration file the attribute weight category
> *int_area_ratio*. The User's Guide does not give an adequate
explanation of
> this attribute: "the intersection divided by the minimum object area
> ratio". What does that mean?  Should this actually be "the ratio of
the
> area of intersection to the union area"? Please clarify. Thanks.
> ratio
> Jeff Duda
>
> --
> Jeff Duda
> Post-doctoral research fellow
> University of Oklahoma School of Meteorology
>
>

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