Sources and uses of digital information are in-scope for this blog, and a great example just showed up in my RSS reader today.
This project is truly a product of the early 21st century: it requires GPS satellites, cheap but accurate GPS receivers, the World Wide Web, inexpensive computers with fast color graphics, and so forth.
And like all modern geographic applications, it also exploits a special property of GPS’s information domain: everyone agrees on the meaning of geographical location; only dates and times have a similar level of standardization. In relational-database terminology, this means that any table with a date or location column has a meaningful join with any other.
This doesn’t work with most data. I’ve had driver’s licenses in four U.S. states, but you can’t aggregate my driving record from the state records because they all use different ID numbering schemes (nice for my privacy in this case).
Also noteworthy is the fact that GPS information can be used to put a time dimension into maps, since we can tell when the street is used as well as where it is. There are some very pretty examples at Cabspotting.