README.md

Plotting Node Density

1. download the source data

    wget http://fred.dev.openstreetmap.org/density/tiles.13
    wget http://fred.dev.openstreetmap.org/density/tiles.16
   

2. convert to simple, gnuplot-readable text format

    sed 's/\([0-9]*\) z=\([0-9]*\) x=\([0-9]*\) y=\([0-9]*\)/\3 \4 \1/' < tiles.13 > tiles.13.txt
    sed 's/\([0-9]*\) z=\([0-9]*\) x=\([0-9]*\) y=\([0-9]*\)/\3 \4 \1/' < tiles.16 > tiles.16.txt
   

3. start gnuplot

    gnuplot
   

4. use gnuplot to create the map

    reset
    unset xtics
    unset ytics
    unset border
    unset key
    unset legend
    unset title
    set lmargin at screen 0
    set tmargin at screen 0
    set rmargin at screen 1
    set bmargin at screen 1
    
    set palette rgbformulae 34,35,36
    
    width = 1024
    
    set xrange [0:width-1]
    set yrange [0:width]
    
    set object rectangle from screen 0,0 to screen 1,1 fillcolor rgb"#000000" behind
    
    set terminal png size width,width
    set output "density.13.png"
    
    plot 'tiles.13.txt' using ($1/8):(width-1-$2/8):(log($3)) with dots palette
   

5. repeat with zoom-16 tiles (don't forget to adapt the numbers above)

6. results and more information