[R-sig-Geo] Map projection

Roger Bivand Roger.Bivand at nhh.no
Mon Oct 23 18:33:28 CEST 2006

On Mon, 23 Oct 2006, bertrand toupin wrote:

> Hi, earlier, I used those functions to transform a lat-long database to a Lambert Azimuthal Equal Area (LAEA) :
> Lam_proj <- project(cbind(Grille$x, Grille$y),"+proj=laea
> +lat_0=latitudem_grid +lon_0=longitudem_grid +x_0=0 +y_0=0 +a=6370997
> +b=6370997 +units=m")
> Now that my calculations is done, I'd like to show the result and I'd need to re-transform the LAEA database to a lat-long database (since "surfm" in Matlab needs lat-long).
> I used : project(cbind(Prev$x, Prev$y),"+proj=latlong")


and see inv=

That is:

project(cbind(Prev$x, Prev$y), proj=paste("+proj=laea", 
"+lat_0=latitudem_grid +lon_0=longitudem_grid +x_0=0 +y_0=0",
"+a=6370997 +b=6370997 +units=m"), inv=TRUE))

> But I got this error message : "latitude or longitude exceeded limits"

Well, yes, you gave project() LAEA coordinates in metres, and asked it to 
project to +proj=longlat, which would be a null-op anyway, because 
project() only goes to (inv=TRUE) and from longlat. If you need objects 
that "remember" their coordinate reference systems, use sp classes and the 
spTransform() methods in rgdal.


> Thanks for any help!
> ---------------------------------
> 	[[alternative HTML version deleted]]
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo

Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no

More information about the R-sig-Geo mailing list