ggmap: gives error when using open street map as source [closed]

Question

I'm new to R and I'm following this article to learn ggmap.

qmap("Forbidden city",zoom=15)
qmap("Forbidden city",zoom=15, source="osm")

While the first command above works perfectly, the second one gives me an error info:

Map from URL : http://maps.googleapis.com/maps/api/staticmap?center=Forbidden+city& zoom=15&size=%20640x640&maptype=terrain&sensor=false Google Maps API Terms of Service : http://developers.google.com/maps/terms Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Forbidden+city&sensor=false Google Maps API Terms of Service : http://developers.google.com/maps/terms Error: map grabbing failed - see details in ?get_openstreetmap. In addition: Warning message: In download.file(url, destfile = destfile, quiet = !messaging, mode = "wb") : cannot open: HTTP status was '503 Service Unavailable'

Any help is appreciated.

Answer 1

I get the same error, reproducibly.

I think this is to do with the zoom=... specification. This argument is interprested differently depending on the source. When you specify source="osm" the call is routed to get_openstreetmap(...). According to the documentation for that function:

...if you get an error when downloading an openstreetmap the error is attributable to an improper scale specification...

The zoom parameter influences the scale specification if scale="auto" (the default). So basically, if zoom is too large the call will throw an error. I get errors with zoom > 13 for the Forbidden City, but this works:

qmap("Forbidden city",zoom=13, source="osm")