Re: Computing polygon area with decimal degree coordinates

Yes, agreed... I realized that after having formulated the question and 
posted it!!!!

Tim Keitt a écrit :
> Do you mean the flat-plane area or the area projected onto the surface 
> of the ellipsoid? In either case, the computation is likely 
> non-trivial. It makes much more sense to project to UTM and do the 
> calculation there.
>
> THK
>
> On 5/31/06, *Patrick Giraudoux* <patrick.giraudoux@xxxxxxxxxxxxxx 
> <mailto:patrick.giraudoux@xxxxxxxxxxxxxx>> wrote:
>
>     Dear Listers,
>
>     The function areapl() of the package splancs computes polygon
>     areas  in
>     the coordinate units. This means in square meters when using UTM or
>     Lambert projections but in "square degrees" when using longlat
>     degrees.
>
>     Does anybody knows a R function (or an algorithm) to compute the area
>     directly (without projecting or projecting internally), eg in square
>     meters, of a polygon whose node coordinates are given in decimal
>     degrees?
>
>     Thanks for any hint,
>
>     Patrick
>
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>
>
>
> -- 
> Timothy H. Keitt
> http://www.keittlab.org/ 

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