Linear interpolation gets you 9X% of the way there for cheap, though. You can then come up with strategies for attacking the last 10% at somewhat higher cost in

Linear interpolation gets you 9X% of the way there for cheap, though. You can then come up with strategies for attacking the last 10% at somewhat higher cost instead of committing the entire stack to the high-cost strategy. For example, if you ascertain that a bus is more than 2 minutes late, switch to polling that bus more often until it makes it to its next stop. And then switch back to linear interpolation once it gets to that stop. But you'll pay a little bit more for the added accuracy. Morale of the story: if you want to get high-resolution real-time data, you (and your customers) have to pay for it, as that shit ain't easy.