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Last data update: 2014.03.03

R: Download map tiles

openmap

R Documentation

Download map tiles

Description

Downloads map tiles from Openstreetmap.org and other servers.

Usage

	openmap(x, zoom, 
	path="http://tile.openstreetmap.org/",
	maxTiles = 9,
	crs=projection(x),   buffer=0, 
	fact=1, verbose=FALSE)
	osmTiles(name)
	openmapAttribution(name, type=c('text','latex','markdown','html'), short=FALSE)

Arguments

`x`	An `extent` or any spatial object (raster, Spatial*) from which an extent can be obtained.
`zoom`	the zoom level, when missing it will be determined by maxTiles.
`path`	the tile server from which to get the map, see http://wiki.openstreetmap.org/wiki/Tiles#Servers.
`maxTiles`	If zoom is missing, zoom will be chosen such that the number of map tiles is less than or equl to this number.
`crs`	Projection for the output, defaulting to the same projection as `x`. If `x` has no projection, for instance when `x` is a matrix or extent, `crs` is also used as the projection of `x`. If `crs` is missing and `x` has no crs, long-lat is used.
`buffer`	Extend the extent for which the map is requested, in units of `x`. Can be negative, or a vector of length 2 for different x and y extensions
`fact`	Passed to `disaggregate` before reprojecting if `fact>1`, helps to produce a clearer image.
`verbose`	If TRUE, give information on where tiles are coming from, cache hits, etc
`name`	name of a tile path, if missing a vector of all available tile paths is returned. `name` can be any of the names of the vector returned when `name` is unspecified.
`type`	format for the attribution
`short`	short or long attribution

Details

These functions download, display, and manipulate map tiles stored in a standard way either on a web server or a local folder.

Map tiles are a set of PNG images that span the world at a set of zoom levels. Zoom level 1 has four 256x256 pixel tiles in a 2x2 pattern over the whole world. In general, zoom level n has 2^n by 2^n tiles. Zoom levels go up to about 17 or 18 depending on the tile server.

Be sure to attribute any maps you publish, the osmAttribution function will assist.

Value

openmap returns a RasterBrick brick, with 'red', 'green' and 'blue' layers.

Examples



myraster = raster(matrix(0,10,10),xmn=8,xmx=18,ymn=0,ymx=10, 
  crs="+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0")
values(myraster) = seq(0,1,len=ncell(myraster))

myPoints = SpatialPoints(myraster, proj4string=CRS(proj4string(myraster)))[
	seq(1,ncell(myraster),len=5)]

names(osmTiles())

## Not run: 

	mytiles = openmap(myraster)

	map.new(myraster)
	plot(mytiles, add=TRUE)
	points(myPoints,col='red')



	mytiles = openmap(myPoints,
		path=osmTiles("mapquest-sat"), verbose=TRUE)
	map.new(myPoints)
	plotRGB(mytiles, add=TRUE)
	points(myPoints,col='red')
	openmapAttribution(mytiles)

## End(Not run)

openmapAttribution("osm", type='markdown')