In an online GPS tracking system, a fundamental trade-off exists between timeliness , the average time interval between a recorded change in location and a change in the reported location; accuracy , the average error between the actual location and the reported location; and uplink usage , the average amount of data used per second of tracking. While tracking efficiency has been addressed in the literature, our thrifty tracking system presents the first unified view of timeliness, accuracy, and uplink usage, allowing the user to specify desired targets for any two of these objectives, while optimizing the third. We also provide a closed-form characterization of this three-way trade-off, and demonstrate that our system converges to the predicted performance.
