GPS Basemaps in R Using get_map

There are many different maps you can use for a background map for your gps or other latitude/longitude data (i.e. any time you’re using geom_path, geom_segment, or geom_point.)

get_map

Helpfully, there’s just one function that will allow you to query Google Maps, OpenStreetMap, Stamen maps, or CloudMade maps: get_map in the ggmap package. You could also use either get_googlemap, get_openstreetmap, get_stamenmap, or get_cloudmademap, but instead you can just use get_map for the same functionality as all of those combined. This makes it easy to try out different basemaps for your data.

You need to supply get_map with your location data and the color, source, maptype, and zoom of the base map.

Let’s go ahead and map the trails in Elwyn John Wildlife Sanctuary here in Atlanta. The csv data and R file are available in a gist.

gps <- read.csv("elwyn.csv",
  header = TRUE)

library(ggmap)
mapImageData <- get_map(location = c(lon = mean(gps$Longitude),
  lat = 33.824),
  color = "color", # or bw
  source = "google",
  maptype = "satellite",
  # api_key = "your_api_key", # only needed for source = "cloudmade"
  zoom = 17)

pathcolor <- "#F8971F"

ggmap(mapImageData,
  extent = "device", # "panel" keeps in axes, etc.
  ylab = "Latitude",
  xlab = "Longitude",
  legend = "right") +
  geom_path(aes(x = Longitude, # path outline
  y = Latitude),
  data = gps,
  colour = "black",
  size = 2) +
  geom_path(aes(x = Longitude, # path
  y = Latitude),
  colour = pathcolor,
  data = gps,
  size = 1.4) # +
# labs(x = "Longitude",
#   y = "Latitude") # if you do extent = "panel"

We’ll be changing the four lines marked above in orange to change what basemap is used.

source = “google”

get_map option source = “google” (or using get_googlemap) downloads a map from the Google Maps API. The basemaps are © Google. Google Maps have four different maptype options: terrain, satellite, roadmap, and hybrid.

source = “google”, maptype = “terrain”

source = “google”, maptype = “terrain”, zoom = 14

Max zoom: 14

source = “google”, maptype = “satellite”

source = “google”, maptype = “satellite”, zoom = 17

source = “google”, maptype = “roadmap”

source = “google”, maptype = “roadmap”, zoom = 17

source = “google”, maptype = “hybrid”

source = “google”, maptype = “hybrid”, zoom = 17

source = “osm”

get_map option source = “osm” (or using get_openstreetmap) downloads a map from OpenStreetMap. These maps are Creative Commons licensed, specifically Attribution-ShareAlike 2.0 (CC-BY-SA). This means you are free to use the maps for commercial purposes, as long as you release your final product under the same Creative Commons license. OpenStreetMap has no maptype options.

source = “osm” (no maptype needed)