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.
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 = NULL, color = c("color", "bw"), ...)a ggmap object (a classed raster object with a bounding box attribute)
a bounding box in the format c(lowerleftlon, lowerleftlat, upperrightlon, upperrightlat)
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.
character string providing image format - png, jpeg, svg, pdf, and ps formats
turn messaging on/off
return url only
destination file for download (file extension added according
to format). Default NULL means a random tempfile.
color or black-and-white
...
David Kahle david.kahle@gmail.com
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.
# get_openstreetmap(urlonly = TRUE)
# osm servers get overloaded, which can result in
# erroneous failed checks
# osm <- get_openstreetmap()
# ggmap(osm)
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