Matlab seems best, here but I get something much closer (168441)  with
areaPolygons because you are reversing lat and lon.
website and areaint uses (lat, lon)
geosphere uses (lon, lat)


On Thu, Oct 25, 2012 at 2:44 PM, c.gutierrez <c74gutierrez@gmail.com> wrote:

> I'm at a bit of a loss here, because if I test a real-life case, I get the
> same results from the Online Geodesic Planimeter page you indicated as I
> get
> from Matlab's areaint() = 162606.10366468679.
>
> >From
> "Enter the vertices as latitude longitude pairs, one per line: "
> 36.96353 -0.4164187
> 36.96273 -0.4161722
> 36.96179 -0.4158859
> 36.96247 -0.4113503
> 36.96429 -0.4115961
> 36.96484 -0.4118041
> 36.96581 -0.4119622
> 36.96562 -0.4133627
> 36.96516 -0.4167762
> 36.96502 -0.4167687
> 36.96459 -0.4167097
> 36.96367 -0.4164608
> 36.96353 -0.4164187
>
> Results:
>
>     STATUS             = OK
>     number of vertices = 13
>     Perimeter (m)      = 1604.00781596
>     area (m^2)         = 162516.702
>
> This seems to suggest that it's the R function(s) that are off, if we take
> Kearney's result to be the best approximation of the truth. Here's what I
> get from the geosphere and splancs functions:
> > areaPolygon(coords)
> [1] 205029.5
>  ... or ...
> > areapl(coords.proj4m) #projected using "+proj=utm +zone=36 +ellps=clrk80
> > +units=m +towgs84=-179.1,-44.7,-302.6 +no_defs"
> [1] 203332.68
>
>
>
> --
> View this message in context:
> http://r-sig-geo.2731867.n2.nabble.com/areaint-in-Matlab-vs-areaPolygon-or-areapl-in-R-tp7581399p7581417.html
> Sent from the R-sig-geo mailing list archive at Nabble.com.
>
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