or “How to use RGL to plot 3d maps of API map tiles”

OK more nerd than ninja. RGL is R’s box of power-tool for 3D object rendering, with functionality for creating 3d mesh objects and curved surfaces, and for using materials and directional lighting. ¬†For example the line:

plot3d(rnorm(100),rnorm(100),rnorm(100))

creates a 3d scatterplot of x-y-z normal distributions, producing:

rgl_basic_example

OpenStreetMap provides a nice way to import map tiles via the OSM API (among others). A helpful StackOverFlower (Spacedman) has provided this useful function for adding ‘z’ values to OSM map objects, enabling them to be plotted in 3d:

map3d <- function(map, ...){
  if(length(map$tiles)!=1){stop("multiple tiles not implemented") }
  nx = map$tiles[[1]]$xres
  ny = map$tiles[[1]]$yres
  xmin = map$tiles[[1]]$bbox$p1[1]
  xmax = map$tiles[[1]]$bbox$p2[1]
  ymin = map$tiles[[1]]$bbox$p1[2]
  ymax = map$tiles[[1]]$bbox$p2[2]
  xc = seq(xmin,xmax,len=ny)
  yc = seq(ymin,ymax,len=nx)
  colours = matrix(map$tiles[[1]]$colorData,ny,nx)
  m = matrix(0,ny,nx)
  surface3d(xc,yc,m,col=colours, ...)
}

A benefit of the approach is that it enables you to adjust the map to the ideal perspective for representing the data in the final rendered image. Here I've applied the function to data on London's rental costs (for the year to December 2012), extruding thick lines for cost comparisons:

rgl_3d_map

The satellite version, simply replacing 'osm' with 'bing' in the code..
rgl_3d_satellite

Code @ Github

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