Hans,

Take a look at the proj4 package, specifically project()

see http://trac.osgeo.org/proj/

There are many projections that allow you to recenter a map on a specific
longitude

For example


x <- seq(-180, 180)
y <- seq(-90, 90)

xy <- expand.grid(x, y)

plot(xy)

mer <- cbind(0, y)  #prime meridian
points(mer[,1], mer[,2], col = "white")


proj.xy <- project(xy, "+proj=eck4") ###project grid into eckert IV
proj.mer <- project(mer, "+proj=eck4") ###project meridian into eckert IV

plot(proj.xy)
points(proj.mer[,1], proj.mer[,2], col = "white")


proj.xy <- project(xy, "+proj=eck4 +lon_0=90W") ###project grid into eckert
IV with central meridian at 90W
proj.mer <- project(mer, "+proj=eck4 +lon_0=90W") ###project meridian into
eckert IV with central meridian at 90W


plot(proj.xy)
points(proj.mer[,1], proj.mer[,2], col = "white")



On Thu, Jan 8, 2009 at 4:07 AM, Hans-Jörg Bibiko <bibiko@eva.mpg.de> wrote:

> Hi,
>
> I wonder if there's a workaround to generate seamless maps based on
> SpatialPolygons objects. E.g. to produce a map showing Australia at the left
> edge and America at the right one ( xlim := min: 110°E , max: 30°W ).
> Or the way around, is there a function to re-center a given map by defining
> the median longitude? (I know the function 'recenter' which produce a map
> from 0° to 360°)
>
> Kind regards,
>
> --Hans
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo@stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>



-- 
Matthew J. Oliver
Assistant Professor
College of Marine and Earth Studies
University of Delaware
700 Pilottown Rd.
Lewes, DE, 19958
302-645-4079
http://www.ocean.udel.edu/people/profile.aspx?moliver

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