ggmap (version 4.0.0)

OSM_scale_lookup: Look up OpenStreetMap scale for a given zoom level.

Description

Look up OpenStreetMap scale for a given zoom level.

Usage

OSM_scale_lookup(zoom = 10)

Value

scale

Arguments

zoom

google zoom

Author

David Kahle

Details

The calculation of an appropriate OSM scale value for a given zoom level is a complicated task. For details, see https://wiki.openstreetmap.org/wiki/FAQ

Examples

OSM_scale_lookup(zoom = 3)
OSM_scale_lookup(zoom = 10)

if (FALSE) {
# these can take a long time or are prone to crashing
# if the osm server load is too high

# these maps are were the ones used to tailor fit the scale
# the zooms were fixed
ggmap(get_map(zoom =  3, source = 'osm', scale = 47500000), extent = "device")
ggmap(get_map(zoom =  4, source = 'osm', scale = 32500000), extent = "device")
ggmap(get_map(zoom =  5, source = 'osm', scale = 15000000), extent = "device")
ggmap(get_map(zoom =  6, source = 'osm', scale = 10000000), extent = "device")
ggmap(get_map(zoom =  7, source = 'osm', scale =  5000000), extent = "device")
ggmap(get_map(zoom =  8, source = 'osm', scale =  2800000), extent = "device")
ggmap(get_map(zoom =  9, source = 'osm', scale =  1200000), extent = "device")
ggmap(get_map(zoom = 10, source = 'osm', scale =   575000), extent = "device")
ggmap(get_map(zoom = 11, source = 'osm', scale =   220000), extent = "device")
ggmap(get_map(zoom = 12, source = 'osm', scale =   110000), extent = "device")
ggmap(get_map(zoom = 13, source = 'osm', scale =    70000), extent = "device")
ggmap(get_map(zoom = 14, source = 'osm', scale =    31000), extent = "device")
ggmap(get_map(zoom = 15, source = 'osm', scale =    15000), extent = "device")
ggmap(get_map(zoom = 16, source = 'osm', scale =     7500), extent = "device")
ggmap(get_map(zoom = 17, source = 'osm', scale =     4000), extent = "device")
ggmap(get_map(zoom = 18, source = 'osm', scale =     2500), extent = "device")
ggmap(get_map(zoom = 19, source = 'osm', scale =     1750), extent = "device")
ggmap(get_map(zoom = 20, source = 'osm', scale =     1000), extent = "device")

# the USA
lonR <- c(1.01,.99)*c(-124.73,-66.95)
latR <- c(.99,1.01)*c(24.52, 49.38)
qmap(lonR = lonR, latR = latR, source = 'osm', scale = 325E5)

}