[GRASSLIST:7005] Re: calculating center of intensity

[Thomas Adams]

Jason,

Not that I have the best answer for you (although I am interested in 
what you are doing with your reference to 'NEXRAD RADAR'); it seems to 
me that you may need to set some threshold to the raster to identify the 
cells and then do a raster to vector conversion from which you can 
identify the polygon centroids. Just a thought...

Regards,
Tom


Jason Horn wrote:

> John, 
>
> Thanks for the response.  By center, I did not mean the geometric 
> centroid, rather the center of intensity based on pixel values.  For 
> reference, if you've ever used IDRISI, something like their CENTER module:
>
> "center 
> Compute mean center (weighted or not) of a point distribution and 
> standard radius (the two dimensional equivalent of a standard deviation)."
>
> I have worked with folks in the Geography department, and I know that 
> this sort of thing is relatively easy mathematically, I just wanted to 
> know if it was possible with GRASS 6.0 as it is.
>
> - Jason
>
>
> On Jun 2, 2005, at 3:51 PM, Jonathan Greenberg wrote:
>
>> Jason:
>>
>>     What do you mean by center?  Are you referring to a geometric 
>> centroid, or the brightest pixel value falling within a poly, or 
>> something else?  Have you chatted with any of the RS people at BU? 
>>  BU has one of the best remote sensing programs in the country (its 
>> also my alma mater).  
>>
>> --j
>>
>>
>> On 6/2/05 12:42 PM, "Jason Horn" <jhorn at bu.edu <mailto:jhorn at bu.edu>> 
>> wrote:
>>
>>> Does anyone know of a way to calculate the center of a shape in a 
>>> raster file based on shape and pixel values?  For example, imagine a 
>>> NEXRAD RADAR image showing a storm cloud.  Could GRASS be used to 
>>> calculate the center of the cloud?  I'm not having any luck finding 
>>> a grass raster function to do this.
>>>
>>> Thanks, 
>>>
>>> - Jason
>>>
>>>
>>>  
>>>
>>> Jason Horn
>>>
>>>
>>> Boston University Department of Biology
>>>
>>>
>>> 5 Cumington Street  Boston, MA 02215
>>>
>>>
>>>
>>>  
>>>
>>> jhorn at bu.edu <mailto:jhorn at bu.edu>
>>>
>>>
>>> office: 617 353 6987
>>>
>>>
>>> cell: 401 588 2766
>>>
>>>  
>>>
>>>
>>
>>
>>
>> -- 
>> Jonathan A. Greenberg, PhD
>> NRC Research Associate
>> NASA Ames Research Center
>> MS 242-4
>> Moffett Field, CA 94035-1000
>> 650-604-5896
>> AIM: jgrn307
>> MSN: jgrn307 at hotmail.com <mailto:jgrn307 at hotmail.com>
>
>

-- 
Thomas E Adams
National Weather Service
Ohio River Forecast Center
1901 South State Route 134
Wilmington, OH 45177

EMAIL:	thomas.adams at noaa.gov

VOICE:	937-383-0528
FAX:	937-383-0033

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