[R-sig-Geo] Computing polygon area with decimal degree coordinates

[Patrick Giraudoux]

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