How to create a KML file using R

Question

I have written a R script to get some map point data (Latitude and Longitude values). I am able to plot them in R and visualize them. But now I want to generate a KML file from this data and view using Google Earth. So that I can share it with colleagues and they can see it on Google Earth too.

What is the best method / package to do this ?

Answer 1

Check the writeOGR function in the rgdal package. Here is a simple example:

library("sp")
library("rgdal")
data(meuse)
coordinates(meuse) <- c("x", "y")
proj4string(meuse) <- CRS("+init=epsg:28992")
meuse_ll <- spTransform(meuse, CRS("+proj=longlat +datum=WGS84"))
writeOGR(meuse_ll["zinc"], "meuse.kml", layer="zinc", driver="KML") 

The objects exported are SpatialPointsDataFrame, SpatialLinesDataFrame, or SpatialPolygonsDataFrame objects as defined in the sp package.

R> class(meuse)
[1] "SpatialPointsDataFrame"
attr(,"package")
[1] "sp"

For writing with the KML driver, note that the geometries should be in geographical coordinates with datum WGS84.

Answer 2

I think is worth mentioning the plotKML package as well.

However, for easy sharing among colleagues I found interesting the mapview package based on leaflet package. One can save a map as HTML document with various options for a background map; no need of Google Earth and the HTML map will run on your browser.

Some examples:

library(sp)
library(rgdal)
library(raster)
library(plotKML)
library(mapview)

# A SpatialPointsDataFrame example
data(meuse)
coordinates(meuse) <- ~x+y
proj4string(meuse) <- CRS("+init=epsg:28992") # CRS Amersfoort (Netherlands)
# make a KML file from SpatialPointsDataFrame object
# will get a warning like "Reprojecting to +proj=longlat +datum=WGS84 ..."
# as it is expected to work with geographical coordinates with datum=WGS84, 
# but seems that it takes care of the reprojecting. 
plotKML::kml(meuse,
             file.name    = "meuse_cadium.kml",
             points_names = meuse$cadmium,
             colour    = "#FF0000",
             alpha     = 0.6,
             size      = 1,
             shape     = "http://maps.google.com/mapfiles/kml/pal2/icon18.png")
# Or, an easy to make interactive map with mapView()
mapView(meuse)

# A RasterLayer example   
data(meuse.grid)
gridded(meuse.grid) <- ~x+y
proj4string(meuse.grid) <- CRS("+init=epsg:28992")
dist_rst <- raster(meuse.grid["dist"])
# make a KML file from RasterLayer object
plotKML::kml(dist_rst,
             file.name    = "dist_rst.kml",
             colour_scale = SAGA_pal[[1]])
# Or, easy to make interactive map with mapView() - display raster and add the points
mapView(dist_rst, legend=TRUE) + meuse
# However, note that for bigger raster datasets mapView() might reduce from resolution

More examples with plotKML here, with a tutorial here. For mapview, an intro can be found here.