Downloads a basemap for map.ppi()
from Stamen Maps or Google Maps using
ggmap::get_map()
. To use Google Maps as source
, you will have to register
with Google, enable billing and provide an API key to ggmap. See the ggmap README for details.
download_basemap(
x,
verbose = TRUE,
zoom,
alpha = 1,
source = "stamen",
maptype = "terrain",
...
)
A ppi
object.
Logical. When TRUE
, prints information to console.
Integer. Optional zoom level from 3 (continent) to 21 (building),
see ggmap::get_map()
. When undefined, the zoom level will be the one
matching the ppi
extent.
Numeric. Transparency of the basemap, value between 0 and 1.
Character. Map service to be used: stamen
or google
.
Character. Type of basemap to plot. For Stamen Maps:
terrain
, terrain-background
, terrain-labels
, terrain-lines
,
toner
, toner-2010
, toner-2011
, toner-background
, toner-hybrid
,
toner-labels
, toner-lines
, toner-lite
or watercolor
. For Google
Maps: terrain
, satellite
, roadmap
or hybrid
.
Arguments to pass to ggmap::get_map()
.
A ggmap object for map(ppi)
# Project a scan as a ppi
ppi <- project_as_ppi(example_scan)
# \donttest{
# Create a basemap that matches the extent of the ppi
basemap <- download_basemap(ppi)
#> Downloading zoom = 9 ...
#> ℹ Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL.
# Map the radial velocity of the ppi onto the basemap
map(ppi, map = basemap, param = "VRADH")
# Increase the transparency of the basemap
basemap <- download_basemap(ppi, alpha = 0.3)
#> Downloading zoom = 9 ...
#> ℹ Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL.
map(ppi, map = basemap, param = "VRADH")
# Download a different type of basemap, e.g. a gray-scale image.
# See get_map() in ggmap library for full documentation of the options.
basemap <- download_basemap(ppi, maptype = "toner-lite")
#> Downloading zoom = 9 ...
#> ℹ Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL.
map(ppi, map = basemap, param = "VRADH")
# }