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I am looking for a way in R to project WGS84 latitudes and longitudes to a UTM grid and then convert the UTM coordinates back to the WGS84 latitudes and longitudes. I have found a number of ways to project to a UTM grid (mapproj::mapproject, rgdal::spTransform), but going from the grid back to latitudes and longitudes seems to be more complicated. Is there a projection function that offers the inverse?

I would like to use find the reverse of this:

newdata <-mapproject(dataset$lon, dataset$lat, projection = "lambert", parameters = c(mean(dataset$lon), mean(dataset$lat)))
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    What have you researched so far? There are plenty of places with the generic algorithm for this as well as code snippets of the transformation in various languages.
    – ed.hank
    Jan 6, 2016 at 20:04
  • Can you please point me to a place that shows how to do this in R? I am obviously not looking the right way as I haven't found the answer.
    – rachael orben
    Jan 6, 2016 at 21:12
  • When I get back to the office I can go through my bookmarks, I am pretty sure I have something in there.
    – ed.hank
    Jan 6, 2016 at 21:45
  • are you looking for something like that spTransform(x, CRS("+proj=longlat +ellps=WGS84 +datum=WGS84")) ?
    – MLavoie
    Jan 7, 2016 at 0:15

1 Answer 1

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You can move from any CRS to another CRS, below R code will work. Make sure you know the EPSG code for CRS which you are using. This is a reproducible example for converting from BNG to WGS. Vice versa is also possible.

library(raster)
t<-as.data.frame(matrix(c(531366.2,531325.7,259349.5,249798),nrow=2)) #sample coordinates
colnames(t) = c("x", "y")
t_wgs<-spTransform(SpatialPointsDataFrame(t[,c(1,2)],data = t,proj4string = crs("+init=epsg:27700")) , crs("+init=epsg:4326"))
t_wgs$lon<-t_wgs@coords[,1]
t_wgs$lat<-t_wgs@coords[,2]
View(t_wgs@data)

EPSG code for BNG is 27000 and WGS84 is 4326

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