Cache maps using ggmap

Question

I draw cards using the package ggmap. To download a map over the Internet, I can use this code:

library(ggmap)
get_map(location = c(-1.81, 55.655), zoom = 12, maptype = "hybrid")

Is there a way to avoid downloading maps over the Internet and import the .png file from a local folder instead? Or, in other words, download maps once, cache .png and then import .png from a local folder? My connection is rather slow, I constantly overload the same base card, wasting precious time.

Answer 1

Since the Rget_map object returns , you can save it to disk and reuse later if you want:

> x <- get_map(location = c(-1.81, 55.655), zoom = 12, maptype = "hybrid")
Map from URL : http://maps.googleapis.com/maps/api/staticmap?center=55.655,-1.81&zoom=12&size=%20640x640&scale=%202&maptype=hybrid&sensor=false
Google Maps API Terms of Service : http://developers.google.com/maps/terms
> str(x)
 chr [1:1280, 1:1280] "#122C38" "#122C38" "#122C38" "#122C38" ...
 - attr(*, "class")= chr [1:2] "ggmap" "raster"
 - attr(*, "bb")='data.frame':  1 obs. of  4 variables:
  ..$ ll.lat: num 55.6
  ..$ ll.lon: num -1.92
  ..$ ur.lat: num 55.7
  ..$ ur.lon: num -1.7

x saveRDS readRDS R. POC:

> t <- tempfile()
> saveRDS(x, file = t)
> x <- readRDS(t)
> ggmap(x)

Answer 2

2+ , , ggmap. . Google , ; ggmap .

get_map Google, get_googlemap, archiving = TRUE. , Google Maps (ToS) (). , ToS (21 2015 .) , 30 . , .

library(ggmap)
## get_map() as in the question
foo1 <- get_map(location = c(-1.81, 55.655), zoom = 12, maptype = "hybrid")

## This will store map tiles locally, used by any repeated calls
foo2 <- get_googlemap(center = c(-1.81, 55.655), zoom = 12,
                      maptype = "hybrid", archiving = TRUE, force = FALSE)

identical(foo1, foo2) # TRUE

. , :

## Get roughly the same area as in the Google map
bbox <- c(left=-1.88, bottom=55.625, right=-1.74, top=55.685)
## Broken in ggmap 2.6.1, try GitHub version (which may have other problems)
foo3 <- get_map(location = bbox, zoom = 13, crop = FALSE,
                source = "stamen", maptype = "terrain", force = FALSE)

## Compare the two map sources / types
dev.new()
print(ggmap(foo2))
dev.new()
print(ggmap(foo3))