Here is an updated sense of where I'm at. I decided to re-read in my data file using ReadOGR.

MyDataFile <- read.csv("reduced1.csv")

writeOGR(MyDataFile, "Folder", "File", driver = "ESRI Shapefile")

Checking the CRS at this point gives me 'NA' so I try and assign it

Redefined <- readOGR(dsn="Folder", layer = "File")
proj4string(Redefined) <- CRS("+init=epsg:4326") # WGS 84

[1] "+init=epsg:4326 +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"

Now for reading in my boundaries file:

Map <-readOGR(".","infuse_dist_lyr_2011")

[1] "+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +datum=OSGB36 +units=m +no_defs +ellps=airy +towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894"

So now to transform.

NewMap <- spTransform(Map, proj4string(Redefined))
  • The CRS function doesn't apply to sp-class objects, its applied to strings to create CRS objects. Use proj4string(map) or raster::projection(map) to get the projection string of an sp-class object. That's where your warning comes from.
    – Spacedman
    Commented Feb 15, 2017 at 13:48
  • And does CRS(map) really give an error about CRS(h)? We care about precision here...
    – Spacedman
    Commented Feb 15, 2017 at 13:50
  • Apolgies you're correct - I changed the name to map for the purposes of this post but omitted to do so consistently - sorry!
    – Henry Cann
    Commented Feb 15, 2017 at 13:56
  • Also proj4string returns strings which seem to suggest my files are in the right CRS. However the exact string is slightly different each time - wondering if this matters? I.e for my datafile "+proj=utm +zone=10 +datum=WGS84 +units=m +no_defs +ellps=WGS84 +towgs84=0,0,0" whereas for my shapefile +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0" - the latter being shorted and without the zone and unit bits.
    – Henry Cann
    Commented Feb 15, 2017 at 13:58
  • 1
    That sounds like you've got the wrong proj4string assigned to some data. If you read with readOGR or raster::shapefile it should pick up the projection from the .prj file. In your rewrite, show the output of summary on your spatial objects.
    – Spacedman
    Commented Feb 15, 2017 at 17:58

1 Answer 1


Try reading the layers using rgdal::readOGR , this reads the projection automatically and is (IMO) more robust that readShapePoly.

Then if needed, run spTransform with one of your layers as the "to" option.

  • Tom, I will try readOGR for my shapefile but what about my datafile initially read in from csv? Can readOGR be used?
    – Henry Cann
    Commented Feb 15, 2017 at 13:44
  • Just to add that I followed the advice of using ReadOGR with both files. I then was able to use sp Transform into epsg:4238 for both. However for the datafile, which already had the right coordinates, the coordinate column has now gone awry. E.g the first entry reads -127.4887 0.00042064 where it used to be in degrees decimal
    – Henry Cann
    Commented Feb 15, 2017 at 14:33
  • I'm slightly confused over what your problem is now. The co-ordinates will change to match to new projection system. Are the data appearing where you would expect when plotted? Commented Feb 16, 2017 at 15:16

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