openmap function

Download map tiles

Downloads map tiles from Openstreetmap.org and other servers.

openmap(x, zoom, 
          path="http://tile.openstreetmap.org/",
          maxTiles = 9, 
          crs=ifelse(is.numeric(x), mapmisc::crsLL, terra::crs(x)),   
          buffer=0, fact=1, 
                verbose=getOption('mapmiscVerbose'),
          cachePath=getOption('mapmiscCachePath'),
          suffix=NULL
)

        osmTiles(name, xyz, suffix)

        openmapAttribution(name, 
          type=c('text','latex','markdown','html', 'auto'), 
          short=FALSE)

Arguments

• x: An a spatial object from which an extent and crs can be obtained.
• zoom: the zoom level, when missing it will be determined by maxTiles.
• path: Source of map tiles, see http://diseasemapping.r-forge.r-project.org/mapLayers.html.
• 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 NA or 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 increase or decrease resolution, values above 1 help to produce a clearer image.
• verbose: Print information about map images being downloaded, defaults to FALSE.
• cachePath: Location to store downloaded map images, defaults to tempdir()
• 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
• xyz: format of xyz coordinates in URL's
• suffix: string to append to URL's, i.e. '.png'

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.

See https://mc.bbbike.org/mc/ for a more possible map tiles (not all of which are compatible with openmap)

Be sure to attribute any maps you publish, the osmAttribution function will assist. If type = 'auto' then markdown format will be used unless a variable mdToTex is defined and equal to TRUE.

Returns

openmap returns a SpatRaster with indexed colours or RGB layers.

openmapAttribution returns a character string.

Examples

data("netherlands")
nldTiles = terra::unwrap(nldTiles)
plot(nldTiles)

openmapAttribution('osm', short=TRUE, type='markdown')

openmapAttribution("stamen-watercolor", type='text')

myraster = rast(matrix(1:100,10,10),extent=ext(8, 18, 0, 10), crs=crsLL)

myPoints = as.points(myraster)[seq(1, ncell(myraster), len=12)]

names(osmTiles())

        mytiles = try(openmap(myraster, zoom=5, verbose=TRUE))

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

        myPoints = project(myPoints, crsMerc)
        map.new(myPoints)

        mytiles = try(openmap(myPoints,
                path='https://livemap-tiles1.waze.com/tiles', verbose=TRUE, buffer=5))
        plot(mytiles, add=TRUE)

        points(myPoints, col='red')

par(oldpar)