A vector space model for automatic indexing
Communications of the ACM
Use of the Hough transformation to detect lines and curves in pictures
Communications of the ACM
Pattern Classification (2nd Edition)
Pattern Classification (2nd Edition)
Proceedings of the 3rd international conference on Embedded networked sensor systems
Telos: enabling ultra-low power wireless research
IPSN '05 Proceedings of the 4th international symposium on Information processing in sensor networks
Fidelity and yield in a volcano monitoring sensor network
OSDI '06 Proceedings of the 7th USENIX Symposium on Operating Systems Design and Implementation - Volume 7
Wireless sensor networks for soil science
International Journal of Sensor Networks
Towards clock skew based services in wireless sensor networks
International Journal of Sensor Networks
Phoenix: an epidemic approach to time reconstruction
EWSN'10 Proceedings of the 7th European conference on Wireless Sensor Networks
On-the-Fly calibration of low-cost gas sensors
EWSN'12 Proceedings of the 9th European conference on Wireless Sensor Networks
Hi-index | 0.00 |
This paper investigates postmortem timestamp reconstruction in environmental monitoring networks. In the absence of a time-synchronization protocol, these networks use multiple pairs of (local, global) timestamps to retroactively estimate the motes' clock drift and offset and thus reconstruct the measurement time series. We present Sundial , a novel offline algorithm for reconstructing global timestamps that is robust to unreliable global clock sources. Sundial reconstructs timestamps by correlating annual solar patterns with measurements provided by the motes' inexpensive light sensors. The surprising ability to accurately estimate the length of day using light intensity measurements enables Sundial to be robust to arbitrary mote clock restarts. Experimental results, based on multiple environmental network deployments spanning a period of over 2.5 years, show that Sundial achieves accuracy as high as 10 parts per million (ppm), using solar radiation readings recorded at 20 minute intervals.