Dear Roger, Many thanks for your rapid reply! I guess I was so caught up in the details of rgdal that I completely failed to see that obvious problem. I've managed to fix the coordinates, and now rgdal reads the image just fine.
I'm still searching for a good overview of rgdal or gdal though - any pointers would be wonderful. Sincerely, Matt Roger Bivand wrote: > On Wed, 11 Jul 2007, Matthew Landis wrote: > >> Dear R-sig-Geo, >> >> I'm trying to get started with rgdal, and not having much luck so far. >> I'm running R 2.5.0 on an i386-pc-mingw32 with rgdal 0.5-9 and sp >> 0.9-14. >> >> For starters, I'd like to read in an .img file created in ArcGIS 9.2. As >> you can see below, the file is a global map in geographic coordinates >> with 0.5 degree resolution. >> >> > GDALinfo('swe20070615.img') >> Closing GDAL dataset handle 0x020d8660... destroyed ... done. >> rows 360 >> columns 720 >> bands 1 >> ll.x -180 >> ll.y 90.0321 > > This is the problem, since > 90N is not defined for geographical > coordinates, and leads to the projection being rejected. Why Arc wants > to believe in > 90N is probably not known. If you can find out where > the fuzz is coming from, perhaps you can remove it? If correcting the > data is not an option, please ask again, and a work-round may be > possible (reading the data without its projection information, and > placing it in a correct grid). > > Roger > >> res.x 0.5 >> res.y 0.5 >> oblique.x 0 >> oblique.y 0 >> driver HFA >> projection +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs >> file swe20070615.img >> >> The result of readGDAL is initially promising, but ultimately fails, >> apparently due to a problem with the projection. >> >> > test <- readGDAL('swe20070615.img') >> swe20070615.img has GDAL driver HFA >> and has 360 rows and 720 columns >> Closing GDAL dataset handle 0x056988a8... destroyed ... done. >> Closing GDAL dataset handle (nil)... done. >> Closing GDAL dataset handle 0x020dade8... destroyed ... done. >> Closing GDAL dataset handle 0x05699470... destroyed ... done. >> Error in `proj4string<-`(`*tmp*`, value = <S4 object of class "CRS">) : >> Geographical CRS given to non-conformant data >> > str(test) >> Error in str(test) : object "test" not found >> >> Can anyone suggest what might be going wrong and how to fix it? >> >> In addition, I've had some trouble finding a good point of entry for how >> to use rgdal. I have checked the standard documentation in the R help >> files and the GDAL websites, but having a bit of trouble penetrating it >> all. If anyone can point me to a concise overview of how to use rgdal, >> I'd be most grateful. >> >> Many thanks in advance, >> >> Sincerely, >> >> Matt Landis >> >> > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo