If you have a sufficiently large deployment, there's a pretty good chance that at any point in time some of the phones will be stationary. Filtering out the fas

If you have a sufficiently large deployment, there's a pretty good chance that at any point in time some of the phones will be stationary. Filtering out the fast-moving ones is pretty easy, leaving the stationary and slow-moving ones. The whole reason technologies like DGPS work is because receivers in roughly the same location will have roughly the same offset. If you average out the stationary receivers, you will be left with a shared common drift - which can be corrected for. Slow-moving receivers probably don't affect the average too much, and you'd be able to filter them out over time as they'd have movement beyond the shared common drift. Devices will enter the stationary set as they stop moving, and move out of it as they start moving again. Even someone stopped at a traffic light for a few dozen seconds might be able to contribute to it.