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UTM to longlat

9 messages · milton ruser, Edzer Pebesma, Renaud Lancelot +2 more

Original
Renaud Lancelot
# 
Dear all,

I have a big dataset (> 200,000 lines) of georeferenced locations where 
the coordinates are given in UTM, spanning over several zones. Is is 
possible to convert all the UTM coordinates into longlat WGS84 with a 
single call ?

Renaud
Edzer Pebesma
# 
Yes, but you will not like that call.

In R (package sp), each spatial data set can only have one single
projection. I'd suggest, in pseudo-code

- import the data into a data.frame
- for each UTM zone do:
   select the locations
   set their CRS
   reproject to long/lat
- cbind the locations to a single data structure
- convert back to data.frame if needed.
--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of M?nster
Weseler Stra?e 253, 48151 M?nster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de/
http://www.springer.com/978-0-387-78170-9 e.pebesma at wwu.de
Renaud Lancelot wrote:
Jim Burke
# 
Its all quite simple I think (i.e. "hope"). Have
you used spTransform(rdgal)?

## here I have a file from a local group delivered
## in UTM format that I transformed OK to long-lat.

library(rgdal) # for map projection support; automatically loads sp
## transform internal measurements from UTM to long lat format
longlat_sp <- spTransform(UTM_format_sp, CRS("+init=epsg:4326"))
sapply(slot(longlat_sp, "polygons"), function(x) slot(x, "ID"))


 > showMethods("spTransform")
Function: spTransform (package rgdal)
x="SpatialGridDataFrame", CRSobj="CRS"
x="SpatialLines", CRSobj="CRS"
x="SpatialLinesDataFrame", CRSobj="CRS"
x="SpatialPixelsDataFrame", CRSobj="CRS"
x="SpatialPoints", CRSobj="CRS"
x="SpatialPointsDataFrame", CRSobj="CRS"
x="SpatialPolygons", CRSobj="CRS"
x="SpatialPolygonsDataFrame", CRSobj="CRS"

Hope this helps,
Jim Burke
Renaud Lancelot wrote:
Roger Bivand
#
On Fri, 8 May 2009, Renaud Lancelot wrote:

            

      
      
      
    

        
Yes, you could use the spRbind() method in maptools:

library(maptools)
set.seed(1)
a <- SpatialPoints(matrix(runif(100), ncol=2))
b <- SpatialPoints(matrix(runif(100), ncol=2))
c <- spRbind(a, b)
plot(c, axes=TRUE)
points(a, col="green")
points(b, col="red")

Roger