get maps

Alex Bushby, Aleks Jovic, Ben Bolker

library(ggmap)

## fake: don't have my API key any more, data is stored
load("tdata/googlemaps.rda")

ggmap package

get raster map tiles from online sources
e.g. digital aerial photographs, satellite imagery, digital pictures, or even scanned maps
plotting via ggplot extensions
also has functions for geolocation and routing.

getting maps

first retrieve an underlying map layer (raster)
various functions to get maps from popular sources:
- Google Maps
- OpenStreetMap
- Stamen Maps

specify coordinates

usually specify latitude/longitude
(negative longtude = west, negative latitude=south)
usually digital (not degrees/minutes/seconds)
occasional confusion: (lat,lon) is common in geographic contexts but (lon,lat) is (x,y)

StamenMap

## specify lat/long bounding box
mapzone <- c(left = -135, bottom = 25.75, right = -62, top = 75)
s_map <- get_stamenmap(mapzone, zoom = 5, maptype = "toner-lite")
## maptype: "terrain", "terrain-background", "terrain-labels", "terrain-lines",
##  "toner" + etc., "watercolor", ...
class(s_map)

## [1] "ggmap"  "raster"

Plot

ggmap(s_map)

Google maps

Need to sign up for an API key and enable various APIs: go here and follow all the instructions (get an API key, enable maps services, give them credit card info …)

register_google(key=Sys.getenv("GOOGLEMAPS_KEY"))
hamilton_map <- get_googlemap(center=c(lon=-79.91, lat=43.26),
                       zoom=13, size=c(640,640),
                       scale=2,maptype='terrain')
## maptype: 'satellite','roadmap','hybrid'

print(hamilton_map)

## 1280x1280 terrain map image from Google Maps. 
## See ?ggmap to plot it.

class(hamilton_map)

## [1] "ggmap"  "raster"

plot

ggmap(hamilton_map)

#zoom must be whole number, so a bit finnicky
#mcmaster satellite map
mcmaster_map <- get_googlemap(center=c(lon=-79.9192, lat=43.2609),
                             zoom=15, maptype = 'satellite')

ggmap(mcmaster_map)

#you can get as close as the database permits
fireball_map <- get_googlemap(center=c(lon=-79.92, lat=43.2609), zoom=19, maptype = 'satellite')

ggmap(fireball_map)

compare stamen

fb_mapzone <- c(left = -79.921, bottom = 43.2603, right = -79.919, top = 43.2615)
## max zoom
s_map2 <- get_stamenmap(fb_mapzone, zoom = 18, maptype = "watercolor")

ggmap(s_map2)

Oh well …

more Google maps tricks

## need "geocoding API" enabled
london_map <- get_googlemap("london england", zoom = 12)
## Las Vegas!
## https://en.wikipedia.org/wiki/New_York-New_York_Hotel_and_Casino
nyny_map <- get_googlemap("newyork newyork", zoom = 12)
to1_map <- get_googlemap('toronto canada', zoom=12,maptype='satellite')
## certain zooms work: zoom=12 does, 13 doesn't, 14 doesn't, 15 does
to2_map <- get_googlemap('toronto canada', zoom=15, maptype='hybrid')