Using Basemaps
Leaflet supports basemaps using map tiles, popularized by Google Maps and now used by nearly all interactive web maps.
Default (OpenStreetMap) Tiles
The easiest way to add tiles is by calling addTiles()
with no arguments; by default, OpenStreetMap tiles are
used.
m <- leaflet() %>% setView(lng = -71.0589, lat = 42.3601, zoom = 12)
m %>% addTiles()Third-Party Tiles
Alternatively, many popular free third-party basemaps can be added
using the addProviderTiles() function, which is implemented
using the leaflet-providers
plugin. See here
for the complete set.
As a convenience, leaflet also provides a named list of all the
third-party tile providers that are supported by the plugin. This
enables you to use auto-completion feature of your favorite R IDE (like
RStudio) and not have to remember or look up supported tile providers;
just type providers$ and choose from one of the options.
You can also use names(providers) to view all of the
options.
m %>% addProviderTiles(providers$Stamen.Toner)m %>% addProviderTiles(providers$CartoDB.Positron)m %>% addProviderTiles(providers$Esri.NatGeoWorldMap)Note that some tile set providers require you to register; see the project
page for more information. You can pass access tokens/keys, and
other options, to the tile provider by populating the
options argument with the
providerTileOptions() function.
Custom Tile URL Template
If you happen to have a custom map tile URL template to use, you can
provide it as an argument to addTiles().
WMS Tiles
You can use addWMSTiles() to add WMS (Web Map Service)
tiles. The map below shows the Base Reflectivity (a measure of the
intensity of precipitation occurring) using the WMS from the Iowa Environmental
Mesonet:
leaflet() %>% addTiles() %>% setView(-93.65, 42.0285, zoom = 4) %>%
addWMSTiles(
"http://mesonet.agron.iastate.edu/cgi-bin/wms/nexrad/n0r.cgi",
layers = "nexrad-n0r-900913",
options = WMSTileOptions(format = "image/png", transparent = TRUE),
attribution = "Weather data © 2012 IEM Nexrad"
)Combining Tile Layers
You aren’t restricted to using a single basemap on a map; you can
stack them by adding multiple tile layers. This generally only makes
sense if the front tiles consist of semi transparent tiles, or have an
adjusted opacity via the options argument.
m %>% addProviderTiles(providers$MtbMap) %>%
addProviderTiles(providers$Stamen.TonerLines,
options = providerTileOptions(opacity = 0.35)) %>%
addProviderTiles(providers$Stamen.TonerLabels)