Re: Computing polygon area with decimal degree coordinates

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> 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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