You have a handful of weather stations, each reporting a temperature at a single point. You need a map that shows temperature everywhere, even in the empty spaces between stations. How do you turn scattered dots into a smooth, continuous surface? That is exactly what this chapter is about — the craft of interpolation. We will start with simple rules of thumb and then learn geostatistical methods that uncover how similarity fades with distance. We will even learn to shift data from one set of area boundaries to another.