get_openstreetmap: Get an OpenStreetMap

Description

get_openstreetmap accesses a tile server for OpenStreetMap and downloads/formats a map image. This is simply a wrapper for the web-based version at http://www.openstreetmap.org/. If you don't know how to get the map you want, go there, navigate to the map extent that you want, click the export tab at the top of the page, and copy the information into this function.

Usage

get_openstreetmap(bbox = c(left = -95.80204, bottom = 29.38048, right =
  -94.92313, top = 30.14344), scale = 606250, format = c("png", "jpeg",
  "svg", "pdf", "ps"), messaging = FALSE, urlonly = FALSE,
  filename = "ggmapTemp", color = c("color", "bw"), ...)

Arguments

bbox

a bounding box in the format c(lowerleftlon, lowerleftlat, upperrightlon, upperrightlat)

scale

scale parameter, see http://wiki.openstreetmap.org/wiki/MinScaleDenominator. smaller scales provide a finer degree of detail, where larger scales produce more coarse detail.

The scale argument is a tricky number to correctly specify. In most cases, if you get an error when downloading an openstreetmap the error is attributable to an improper scale specification. OSM_scale_lookup can help; but the best way to get in the correct range is to go to http://www.openstreetmap.org/, navigate to the map of interest, click export at the top of the page, click 'map image' and then copy down the scale listed.

format

character string providing image format - png, jpeg, svg, pdf, and ps formats

messaging

turn messaging on/off

urlonly

return url only

filename

destination file for download (file extension added according to format)

color

color or black-and-white

...

Value

a ggmap object (a classed raster object with a bounding box attribute)

Details

receive an error message from download.file with the message HTTP status '503 Service Unavailable'. You can confirm this by setting urlonly = TRUE, and then entering the URL in a web browser. the solution is either (1) change sources or (2) wait for the OSM servers to come back up.

See http://www.openstreetmap.org/copyright for license and copyright information.

Examples

Run this code

# NOT RUN {
# }
# NOT RUN {
# osm servers get overloaded, which can result in
# erroneous failed checks

osm <- get_openstreetmap(urlonly = TRUE)
ggmap(osm)

# }
# NOT RUN {
# }