Sign up ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I imported a Shapefile holding a quite detailed world map from:

world = readOGR('./countries_shp/', 'countries')

Using R with the sp-Packages, plotting is really easy:

spplot(world, 'UNREG2')

Now I want to

  • draw a customizable grid
  • add points derived from coordinates

For example importing coordinates of Vienna (48°12′32″N 16°22′21″E) can be done using char2dms of the sp-package:

vienna.N = char2dms("48d12'32\"N")
vienna.E = char2dms("16d22'21\"E")

But how can a draw a point at this exact location on my map?

Also adding a grid is straight forward:

plot(gridlines(world), add=TRUE)

assuming, that the last plot was created with "plot(world)". How can this be achieved with the spplot output?

share|improve this question
Just posting a link to some useful R tricks from a few months ago here:… You can plot points with dismo and ggplot2 (I don't know how to do it in sp). –  djq Apr 5 '12 at 14:43
1 gives an example. You can't mix base graphics with spplot (grid) if that is what your asking. –  Andy W Apr 5 '12 at 14:59
Thanks for the fast answers! I do not want to mix base and sp (lattice) graphics, but draw a customizable grid over/on an spplot. It is very easy using base-graphics (plot) so there just has to be a similar way for the sp package? –  FloE Apr 5 '12 at 15:24
This sounds like a lattice question, pure and simple: you might get a fast authoritative answer over on SO. –  whuber Apr 5 '12 at 15:45
I will try to get an answer there, but I think that the the transformation/projection of the grid is actually a GIS related topic... –  FloE Apr 5 '12 at 16:14

2 Answers 2

up vote 5 down vote accepted

I figured out how to print a point for Vienna on the map.

Importing the coordinates from WikiPedia into R:

vienna.N = char2dms("48d12'32\"N")
vienna.E = char2dms("16d22'21\"E")

Building a sp-object

vienna.coord = data.frame(
coordinates(vienna.coord) = c('x', 'y')

The projection is taken from where the WikiPedia article links to:

proj4string(vienna.coord) = '+proj=latlong +datum=WGS84'

Printing this object gives the numeric representation which equals exactly the data from mentioned website:

> vienna.coord
         coordinates   name
1 (16.3725, 48.2089) Vienna

The resulting

> class(vienna.coord)[1]
[1] "SpatialPointsDataFrame"

can be used with base- and sp-graphics. First we transform the projection to the one used in the Diva worldmap:

vienna.coord = spTransform(vienna.coord, CRS(proj4string(world)))

Then a plot for Europe can be produced:

spplot(world, 'COUNTRY', colorkey=FALSE, 
    xlim=c(-24.5, 69.5), ylim=c(26.6, 71.2),
    sp.layout = c('sp.points', vienna.coord, col='red', pch=16),
    par.settings = list(panel.background=list(col='lightblue')),
    col.regions = rep('white', length(levels(world$COUNTRY)))

world map with red dot for Vienna

share|improve this answer
Very cool! It looks beautiful also. –  djq Apr 5 '12 at 16:33

The part of my questions concerning 'grids' solved itself.

Obviously, the function gridlines generates a rectangular grid for the given projection. A distortion can only be seen after projecting the grid. This might help using 2 projections in one map.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.