GetOsmMap function

Query the Open Street Map server for map tiles instead of Google Maps

The querying parameters for Open Street Maps are somewhat different in this version. Instead of a zoom, center and size, the user supplies a scale parameter and a lat/lon bounding box. The scale determines the image size.

GetOsmMap(lonR = c(-74.02132, -73.98622), latR = c(40.69983, 
    40.72595), scale = 20000, destfile = "MyTile.png", 
    format = "png", RETURNIMAGE = TRUE, GRAYSCALE = FALSE, 
    NEWMAP = TRUE, verbose = 1, ...)

Arguments

• lonR: longitude range
• latR: latitude range
• scale: Open Street map scale parameter. The larger this value, the smaller the resulting map tile in memory. There is a balance to be struck between the lat/lon bounding box and the scale parameter.
• destfile: File to load the map image from or save to, depending on NEWMAP.
• format: (optional) defines the format of the resulting image.
• RETURNIMAGE: return image yes/no default: TRUE
• GRAYSCALE: Boolean toggle; if TRUE the colored map tile is rendered into a black & white image, see RGB2GRAY
• NEWMAP: if TRUE, query the Google server and save to destfile, if FALSE load from destfile.
• verbose: level of verbosity,
• ...: extra arguments to be used in future versions

Returns

map structure or URL used to download the tile.

Author(s)

Markus Loecher

Note

The OSM maptile server is frequently too busy to accomodate every request, so patience is warranted.

Examples

if (0) {
        CologneMap <- GetOsmMap(lonR= c(6.89, 7.09), latR = c(50.87, 51), scale = 150000, 
                            destfile = "Cologne.png");
        PlotOnStaticMap(CologneMap, mar=rep(4,4), NEWMAP = FALSE, TrueProj = FALSE, axes= TRUE);
                
        PrincetonMap <- GetOsmMap(lonR= c(-74.67102, -74.63943), latR = c(40.33804,40.3556), 
                             scale = 12500, destfile = "Princeton.png");
        png("PrincetonWithAxes.png", 1004, 732)
      PlotOnStaticMap(PrincetonMap, axes = TRUE, mar = rep(4,4));
    dev.off()
 }