Some examples of discrete data are the US Census or cows per square mile in Nebraska. Which are size, distribution, pattern, neighborhood, orientation, size, shape, and contiguity. Before these features can be used in a GIS system they must have numbers assigned to them or be encoded. Sources of Data For any kind of research there needs to be data to make it believable. There are countless ways of obtaining data from various sources.
Some sources are maps or books.
Since data is ever-changing one excellent place to obtain up to date current data is the WEB, which houses thousands of online indexes. This data, which is very costly upon demand, is very useful in many research options. ETAK ETAK got its started by developing a car navigation system that got really confused when the car went in reverse. So ETAK took its very large very expensive data bases and turned it into something profitable. ETAK also used Government maps and added information and them sold them.