The plot functions do not automatically transform between coordinate systems, they just assume the space is shared.
yta and vagar share the same PROJ.4 string: identical(proj4string(yta), proj4string(vagar)) [1] TRUE so, assuming that all 3 coordinate systems have been recorded correctly in the .prj files this should be fine: plot(yta) plot(vagar, add = TRUE) sdn.reproj <- spTransform(sdn, CRS(proj4string(vagar))) plot(sdn.reproj, add = T) You are expected to ensure the projections are the same when plotting, or using overlay. I guess it wouldn't take much for those functions to do the job on-the-fly, but often the metadata is non-existent or incorrectly specified and so a manual step like this can save subtle errors. Also, it's much more work to handle rasters with on-the-fly reprojection - it takes a lot more options and is not reversible like vector reprojection often is. Cheers, Mike. On Tue, Nov 17, 2009 at 11:02 AM, Hans Ekbrand <h...@sociologi.cjb.net> wrote: > Hi list, > > I'm a newcomer to GIS and r-sig-geo. I have exported some shapefiles > from ArcGIS and succeeded in plotting them with R. But one shapefile has > a different coordinate system, I think, and it does not turn up in the > graph when added to the others. In ArcGIS, this layer had an "unknown" > coordinate system, but rendered at the right location in relation to the > other layers. > > I have made a tar-archive with the shape-files and a script to import > them into R and generate a map. The problematic shape is "sdn". > > http://sociologi.cjb.net/temp/create-map-data.tbz > http://sociologi.cjb.net/temp/create-map.r > > Here is the summary output of a "good" shape, "yta", followed by summary > of the problematic shape "sdn". > >> summary(yta) > > Object of class SpatialPolygonsDataFrame > > Coordinates: > > min max > > r1 303850 344600.1 > > r2 6388900 6415400.0 > > Is projected: TRUE > > proj4string : > > [+proj=utm +zone=33 +ellps=GRS80 +units=m +no_defs] > > Data attributes: > > KKOD SHAPE_AREA SHAPE_LEN > > Min. :1.000 Min. :7.812e+05 Min. : 3530 > > 1st Qu.:3.000 1st Qu.:1.125e+06 1st Qu.: 5514 > > Median :5.000 Median :3.006e+06 Median : 9121 > > Mean :4.941 Mean :1.272e+09 Mean : 647692 > > 3rd Qu.:7.000 3rd Qu.:1.685e+07 3rd Qu.: 37437 > > Max. :7.000 Max. :3.119e+10 Max. :21081735 > > > >> summary(sdn) > > Object of class SpatialPolygonsDataFrame > > Coordinates: > > min max > > r1 1247825 1288137 > > r2 6382086 6422038 > > Is projected: TRUE > > proj4string : > > [+proj=tmerc +lat_0=0 +lon_0=15.80827777777778 +k=1 +x_0=1500000 +y_0=0 > > +ellps=bessel +units=m +no_defs] > > Data attributes: > > SW_MEMBER NAMN DISTRIKT REG_DATUM DATUM > > Min. : 1 10 Högsbo : 1 Centrum: 4 1996/01/01:21 2001/09/10:21 > > 1st Qu.: 6 11 Älvsborg: 1 Norr :10 > > Median :11 12 Frölunda: 1 Väster : 7 > > Mean :11 13 Askim : 1 > > 3rd Qu.:16 14 Tynnered: 1 > > Max. :21 15 Styrsö : 1 > > (Other) :15 > > OPERATör KVALITET AREA PERIMETER > > eoh:21 Min. :0 Min. : 3729696 Min. :10507 > > 1st Qu.:0 1st Qu.: 9113274 1st Qu.:15376 > > Median :0 Median : 16307500 Median :21493 > > Mean :0 Mean : 34423248 Mean :26351 > > 3rd Qu.:0 3rd Qu.: 34864909 3rd Qu.:32932 > > Max. :0 Max. :198632325 Max. :64221 > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo