http://groups.google.com/group/sci.e...a916915401100a have the right formula?

To quote:

You can use surveyors formula to calculate area of a land parcel.

A = (1/2)[Determinant(x1,x2,y1,y2)+Determinant(x2,x3,y2,y3)+ ...

+Determinant(xn,x1,yn,y1)],

where Determinant(x1,x2,y1,y2) = x1*y2-x2*y1