[R-sig-Geo] UTM to longlat

[Roger Bivand]

On Fri, 8 May 2009, Renaud Lancelot wrote:

> 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?

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

>
> 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
>>>>>
>>>>>
>>>> _______________________________________________
>>>> R-sig-Geo mailing list
>>>> R-sig-Geo at stat.math.ethz.ch
>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>>
>>>>
>>>>
>>>
>>>
>>>
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>>>
>>
>>
>
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no