UTM to longlat

Thank you, here is the full process trying to follow Edzer's suggestion:

library(RODBC)
library(rgdal)
channel <- odbcConnectAccess("farms.mdb")
sigal <- sqlQuery(channel, "select * from T_SIGAL")
Liste <- by(sigal,
           list(zone = sigal$zone),
           function(x){
               strg <- paste("+proj=utm +ellps=intl +zone=",
unique(x$zone), sep = "")
               SP <- SpatialPoints(cbind(x$UTM_X, x$UTM_Y),
proj4string=CRS(strg))
               as.data.frame(spTransform(SP, CRS("+proj=longlat
+datum=WGS84")))
               })
sigal2 <- do.call("rbind", Liste)
dimnames(sigal2) <- list(seq(nrow(sigal2)), c("x", "y"))

Plotting the result looks fine but I need to check further.

BTW, is it possible to stack directly the SpatialPoints objects?

Thank you for your help!

Renaud

2009/5/8 Jim Burke <j.burke at earthlink.net>

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:

Thank you Edzer. I was hoping there was a simpler solution, but it's still
fairly simple.

Renaud

2009/5/7 Edzer Pebesma <edzer.pebesma at uni-muenster.de>

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:

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

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