[R-sig-Geo] Calculating area of polygons

[Wincent]

Thanks Alex.

Also, my object is projected to "Hong Kong 1980 Grid System", so the
unit of area is square meters. Is it a confirmative answer? Thanks
again.

Best
Ronggui

On 15 February 2011 19:57, Alexandre Villers
<villers.alexandre at gmail.com> wrote:
> Good afternoon,
>
> I guess it will be the unit of your original SpatialPolygons object. If you
> use a projected coordinate system, the unit should be in meters, otherwise,
> I'm not sure of this, but it should be in squared degrees.
>
> HTH
>
> Alex
>
> Le 15/02/2011 10:31, Wincent a écrit :
>>
>> The previous email was rejected, so I re-send it. Sorry for disturbing.
>>
>> Regards
>>
>> On 15 February 2011 16:23, Wincent<ronggui.huang at gmail.com>  wrote:
>>>
>>> Dear all,
>>>
>>> According to
>>> https://stat.ethz.ch/pipermail/r-sig-geo/2009-May/005741.html,
>>> the area of polygon can be accessed by
>>>>
>>>> areas<- sapply(slot(scot_BNG, "polygons"), function(x) sapply(slot(x,
>>>> "Polygons"), slot, "area"))
>>>
>>> My question is what is the unit of the area? Is it sq km?
>>> Thank you very much in advance.
>>>
>>> Regards
>>
>>
>



-- 
Wincent Ronggui HUANG (PhD)
Department of Sociology
Fudan University
http://asrr.r-forge.r-project.org/rghuang.html