[R] converting coordinates from utm to longitude / latitude

[Werner Wernersen]

After having figured out that I had to download the proj.dll file additionally (it would be nice if they actually added a note to their readme) and setting the "+south" parameter, the conversion of the shapfile from UTM to long/lat with the ogr2ogr utility from gdal worked perfectly. 

Thanks so much Dylan!
  Werner



----- Ursprüngliche Mail ----
Von: Dylan Beaudette <dylan.beaudette at gmail.com>
An: r-help at r-project.org
CC: Werner Wernersen <pensterfuzzer at yahoo.de>
Gesendet: Dienstag, den 19. August 2008, 23:29:34 Uhr
Betreff: Re: [R] converting coordinates from utm to longitude / latitude

If you would like to convert the entire shapfile check out GDAL:

http://www.gdal.org/

http://casoilresource.lawr.ucdavis.edu/drupal/node/98

Cheers,

Dylan


On Tuesday 19 August 2008, Werner Wernersen wrote:
> It would be nicer to convert directly the entire shapefile object to
> long/lat coordinates but if that is not possible, I will convert the other
> points to UTM. Hence, I am playing around with rgdal.
>
> library(rgdal)
> SP <- SpatialPoints(cbind(32.29252, -0.3228500),
>   proj4string=CRS("+proj=longlat"))
> spTransform(SP, CRS("+proj=utm +zone=36"))
>
> > spTransform(SP, CRS("+proj=utm +zone=36"))
>
> SpatialPoints:
>      coords.x1 coords.x2
> [1,]  421274.4 -35687.37
> Coordinate Reference System (CRS) arguments: +proj=utm +zone=36
> +ellps=WGS84
>
> This result corresponds with what I get when using convUL() but my map of
> that area in UTM coordinates does not extend to the negative. An external
> program converts the point to x=420994   y=9964407 which also seems correct
> with respect to the map. Fore sure, I am using the function wrongly
> somehow. Can anyone give me a hint?
>
> That's very much appreciated!
>
> Thanks,
>    Werner
>
>
>
> ----- Ursprüngliche Mail ----
> Von: Werner Wernersen <pensterfuzzer at yahoo.de>
> An: r-help at stat.math.ethz.ch
> Gesendet: Dienstag, den 19. August 2008, 20:28:29 Uhr
> Betreff: converting coordinates from utm to longitude / latitude
>
> Hi,
>
> is there a function in R to convert data read with read.shape and which is
> originally in UTM coordinates into longitude / latitude coordinates? I
> found the convUL() function from the PBSmapping package but I have no idea
> how I could apply that to the read.shape object.
>
> Many thanks,
>   Werner
>
>
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-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341


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