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WGS84 conversion to UTM

3 messages · Taylor, RB, Ernesto Jardim, Roger Bivand

Original
Taylor, RB
# 
Dear all,

I'm a rather new user to R, so please excuse my ignorance. I understand
in R there are different spatial packages that allow one to do a variety
of spatial analyses. I have collected GPS in WGS84 in South Africa. I
have the data in a tab-deliniated txt file (along with attribute data)
and in .shp files. I want to be able to read the text file (or ascii)
into R and then batch convert long lat to UTM (34 S), and then do some
analyses in R. I can across the website
http://r-spatial.sourceforge.net/xtra/xtra.RHnw.html#spproj, which seems
quite good. But I don't seem to be able to replicate the same procedure
with my files. Being fairly new to R, I am not all that familiar with
the syntax so perhaps this is why I can't do it.

Any help is appreciated,
thanks

PS I work in a windows environment

--
Rob Taylor

University of York
Biology Department
PO Box 373
York
YO10 5YW
United Kingdom

Mob +00 44 079 01531259
Ernesto Jardim
#
Taylor, RB wrote:

            

      
      
      
    

        
Hi Rob,

Take a look at the package "PBSmapping".

You'll need to create a data.frame with the names X and Y and add an
attribute "projection", then just convUL :-)

See my example:

mydf <- read.table(blah, blah, blah)
names(mydf) <- c("X","Y")
attr(mydf, "projection") <- c("LL")
mydf.utm <- convUL(mydf)

Regards

EJ

  
  


  


      

    

    

      
      

        


  

        

      Roger Bivand
    

    

      
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On Thu, 13 Apr 2006, Taylor, RB wrote:

        

            

      
      
      
    

        
The functionality in spproj has recently been moved to rgdal, so that for 
a target UTM zone 34 S:

library(rgdal)
EPSG <- make_EPSG()
EPSG[grep("UTM zone 34S", EPSG$note), 1:2]

gives five alternatives with different ellipsoids. Assuming WGS 84:

utm34S <- CRS("+init=epsg:32734")
showWKT(CRSargs(utm34S))

shows that the EPSG projection has been picked up (EPSG is a long list of 
projections originally created by frustrated oil companies in Europe, 
mostly in the North Sea, because nothing lined up right when they began 
from the coastal states' national grids, etc.).

If your shapefiles have a *.prj file already, readOGR() will pick it up. 
If not, and for the textfiles, you'll need to assign the input coordinate 
reference system to the Spatial object(s):

my_ll <- CRS("+proj=lonlat +datum=WGS84")
proj4string(my_ll_object) <- my_ll

from there it is simple,

my_utm34S_object <- transform(my_ll_object,  utm34S)

Some documentation is coming before (too) long.

Roger