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maphound
(Stranger )
06/20/11 07:31 AM
Re: Area calculations [re: sasnover]Report this article as Inappropriate to us !!!Login to Reply

If you're looking for exact areas, you need an equal area projection. 


But even then they won't agree.  This is because the software will assume a straight line in the current projection.  For sufficiently densified arcs they will agree.     


If you're working with ESRI products, I suppose the closest thing to exact would be Albers Equal Area (based on a cone), because it is the only one that is supported for an ellipsoid.  Lambert Azimuthal Equal Area (based on a plane), and Cylindrical Equal Area (based on a cylinder) are supported only for spheres.  There are some pseudoconic, pseudocylindrical, and pseudoplanar projections -- I think they are supported only for spheres.  There are some equations in one of Snyder's books for ellipsoids in LAEA but they've obviously been too hairy for ESRI to tackle. 


 


 


 






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SubjectPosted byPosted on
*Area calculations sasnover   06/07/11 08:54 AM
.*Re: Area calculations maphound   06/20/11 07:31 AM
.*Re: Area calculations sasnover   06/20/11 08:31 AM
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