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Werner Wernersen | 19 Aug 21:24

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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Werner Wernersen | 20 Aug 00:06

Re: converting coordinates from utm to longitude / latitude

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
(Continue reading)

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Dylan Beaudette | 20 Aug 00:29

Re: 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
(Continue reading)

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Jim Regetz | 20 Aug 04:08

Re: converting coordinates from utm to longitude / latitude

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?

It looks like you are specifying 36S in your external program, and 
(implicitly) 36N in R. Using your SP from above, note the following:

 > spTransform(SP, CRS("+proj=utm +zone=36 +north"))
SpatialPoints:
      coords.x1 coords.x2
[1,]  421274.4 -35687.37
Coordinate Reference System (CRS) arguments: +proj=utm +zone=36
(Continue reading)

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Werner Wernersen | 20 Aug 12:08

Re: converting coordinates from utm to longitude / latitude

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)
(Continue reading)

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Werner Wernersen | 20 Aug 12:03

Re: converting coordinates from utm to longitude / latitude

You were absolutely right. If I use south everything is fine. That once again proves the danger of
intuition. I simply assumed since almost all of the map is on the northern half that the projection should
use north as well. But that is apparently wrong. I couldn't find any description of these definition
string parameters which could have been informative. Since I am not a geographer either, I probably used
the wrong terms for searching.

Anyway, now it works.
Thanks so much for the help, Jim!

Best regards,
  Werner

----- Ursprüngliche Mail ----
Von: Jim Regetz <regetz <at> nceas.ucsb.edu>
An: Werner Wernersen <pensterfuzzer <at> yahoo.de>
CC: r-help <at> stat.math.ethz.ch
Gesendet: Mittwoch, den 20. August 2008, 03:08:48 Uhr
Betreff: Re: converting coordinates from utm to longitude / latitude

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"))
> 
>
(Continue reading)

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Werner Wernersen | 20 Aug 12:59

Re: converting coordinates from utm to longitude / latitude

I forgot one more potentially time-saving hint if someone else wants to use org2org for such a conversion: 
I found that only GDAL for Windows 1.4.4 works together with the proj.dll file which is downloadable from
proj.4 but version 1.5 does not. 

----- 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"))
(Continue reading)

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Gmane