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In this post I way to share with you some code to use Openstreetmap – maps as a backdrop for a data visualization. We will use the RgoogleMaps-package for R. In the following I will show you how to make this graph.

I wanted to take a closer look at an area around my former neighborhood, which is in Bochum, Germany.

lat_c<-51.47393
lon_c<-7.22667
bb<-qbbox(lat = c(lat_c+0.01, lat_c-0.01), lon = c(lon_c+0.03, lon_c-0.03))

Once this is done, you can download the corresponding Openstreetmap tile with the following line.

OSM.map<-GetMap.OSM(lonR=bb$lonR, latR=bb$latR, scale = 20000, destfile=”bochum.png”)

## 2. Add some points to the graphic

Now your second step will most likely be adding points to the map. I choose the following two.

lat <- c(51.47393, 51.479021)
lon <- c(7.22667, 7.222526)
val <- c(10, 100)

As the R-package was mainly build for google-maps, the coordinates need to be adjusted by hand. I made the following functions, that take the min and max value from the downloaded map.

lat_adj<-function(lat, map){(map$BBOX$ll-lat)/(map$BBOX$ll-map$BBOX$ur)}
lon_adj<-function(lon, map){(map$BBOX$ll-lon)/(map$BBOX$ll-map$BBOX$ur)

Now you can add some points to the map. If you want them to mean anything it may be handy to specify an alpha-level and change some aspects of the points, e.g. size, color, alpha corresponding to some variable of interest.

 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22  require(RgoogleMaps)   #define the part of the world you want to plot. Here the area around my former home. lat_c<-51.47393 lon_c<-7.22667 bb<-qbbox(lat = c(lat_c+0.01, lat_c-0.01), lon = c(lon_c+0.03, lon_c-0.03))   # download the tile from OSM OSM.map<-GetMap.OSM(lonR=bb$lonR, latR=bb$latR, scale = 20000, destfile="bochum.png") image(OSM.map) #Add some coordinates lat<- c(51.47393, 51.479021) lon<- c(7.22667, 7.222526) val <- c(0, 255)   #function to adjust the coordinates lat_adj<-function(lat, map){(map$BBOX$ll-lat)/(map$BBOX$ll-map$BBOX$ur)} lon_adj<-function(lon, map){(map$BBOX$ll-lon)/(map$BBOX$ll-map$BBOX$ur)}   PlotOnStaticMap(OSM.map, lat = lat_adj(lat, OSM.map), lon = lon_adj(lon, OSM.map), col=rgb(255,0, val,90,maxColorValue=255),pch=16,cex=4)   dev.print(jpeg,"test.jpeg", width=1204, height=644, units="px")