[R-sig-Geo] Transform decimal degrees units in km - ReadOGR & owin{spatstat}

[Aurelie C.Godin]

Dear list,

I am trying to figure out how I can transform my unit of length from decimal
degree to square km when I import the following simple ArcGIS polygon shape. 
Ultimately, I would like to have this information available when I assign
this spatial polygon to my window in spatstat [i.e., Window area = xx square
unit
Unit of length: xx km].

div0A <- readOGR(dsn="Archive", layer="Projections")
> summary(div0A)
Object of class SpatialPolygonsDataFrame
Coordinates:
     min       max
x -80.00 -57.63430
y  66.25  78.16666
Is projected: FALSE 
proj4string :
[+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0]
Data attributes:
       Id      NPAzimutha         UTM20            UTM19           AlberEA      
 Min.   :0   Min.   :348877   Min.   :349232   Min.   :349162   Min.  
:348656  
 1st Qu.:0   1st Qu.:348877   1st Qu.:349232   1st Qu.:349162   1st
Qu.:348656  
 Median :0   Median :348877   Median :349232   Median :349162   Median
:348656  
 Mean   :0   Mean   :348877   Mean   :349232   Mean   :349162   Mean  
:348656  
 3rd Qu.:0   3rd Qu.:348877   3rd Qu.:349232   3rd Qu.:349162   3rd
Qu.:348656  
 Max.   :0   Max.   :348877   Max.   :349232   Max.   :349162   Max.  
:348656 

library(spatstat)
newW2<-as(div0A,"owin")
> newW2
window: polygonal boundary
enclosing rectangle: [-80, -57.6343] x [66.25, 78.16666] units 

Thank you very much in advance,
Aurelie

-----
Aurelie Cosandey-Godin
Ph.D. Student, Department of Biology, Dalhousie University
Industrial Graduate Fellow, WWF-Canada
Email: godina at dal.ca | Web: wormlab.biology.dal.ca

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