Approximate Isocontours and Spatial Summaries for Sensor Networks

We consider the problem of approximating a family of isocontours in a sensor field with a topologically-equivalent family of simple polygons. Our algorithm is simple and distributed, it gracefully adapts to any user-specified representation size k, and it delivers a worst-case guarantee for the quality of approximation. In particular, we prove that the topology-respecting Hausdorff error in our k-vertex approximation is within a small constant factor of the optimal error possible with Theta(k/log m) vertices, where m is the number of contours. Evaluation of the algorithm on real data suggests that the size increase factor in practice is a constant near 2.6, and shows no error increase. Our simulation results using a variety of synthetic and real data show that the algorithm smoothly handles complex isocontours, even for representation sizes as small as 32 or 48. Because isocontours are widely used to represent and communicate bi-variate signals, our technique is broadly applicable to in- network aggregation and summarization of spatial data in sensor networks.

[1]  D. Caron,et al.  Networked Aquatic Microbial Observing System , 2006 .

[2]  Subhash Suri,et al.  Contour Approximation in Sensor Networks , 2006, DCOSS.

[3]  David E. Culler,et al.  Supporting aggregate queries over ad-hoc wireless sensor networks , 2002, Proceedings Fourth IEEE Workshop on Mobile Computing Systems and Applications.

[4]  Leonidas J. Guibas,et al.  Approximating Polygons and Subdivisions with Minimum Link Paths , 1991, Int. J. Comput. Geom. Appl..

[5]  Yong Yao,et al.  The cougar approach to in-network query processing in sensor networks , 2002, SGMD.

[6]  C.-C. Jay Kuo,et al.  Contour line extraction with wireless sensor networks , 2005, IEEE International Conference on Communications, 2005. ICC 2005. 2005.

[7]  K. J. Ellis,et al.  Cattle health monitoring using wireless sensor networks , 2004 .

[8]  Songwu Lu,et al.  Event Contour: An Efficient and Robust Mechanism for Tasks in Sensor Networks , 2004 .

[9]  Stefan Funke,et al.  Topological hole detection in wireless sensor networks and its applications , 2005, DIALM-POMC '05.

[10]  Gaurav S. Sukhatme,et al.  NAMOS: Networked Aquatic Microbial Observing System , 2006 .

[11]  Vinayak S. Naik,et al.  A line in the sand: a wireless sensor network for target detection, classification, and tracking , 2004, Comput. Networks.

[12]  Yong Wang,et al.  Energy-efficient computing for wildlife tracking: design tradeoffs and early experiences with ZebraNet , 2002, ASPLOS X.

[13]  Sándor P. Fekete,et al.  Deterministic boundary recognition and topology extraction for large sensor networks , 2005, SODA '06.

[14]  Joseph S. B. Mitchell,et al.  Simplifying a polygonal subdivision while keeping it simple , 2001, SCG '01.

[15]  Ramesh Govindan,et al.  Localized edge detection in sensor fields , 2003, Ad Hoc Networks.

[16]  Katia Obraczka,et al.  Efficient continuous mapping in sensor networks using isolines , 2005, The Second Annual International Conference on Mobile and Ubiquitous Systems: Networking and Services.

[17]  David H. Douglas,et al.  ALGORITHMS FOR THE REDUCTION OF THE NUMBER OF POINTS REQUIRED TO REPRESENT A DIGITIZED LINE OR ITS CARICATURE , 1973 .

[18]  Deborah Estrin,et al.  Residual energy scan for monitoring sensor networks , 2002, 2002 IEEE Wireless Communications and Networking Conference Record. WCNC 2002 (Cat. No.02TH8609).

[19]  Jie Gao,et al.  Boundary recognition in sensor networks by topological methods , 2006, MobiCom '06.

[20]  Viktor K. Prasanna,et al.  Constructing Topographic Maps in Networked Sensor Systems , 2004 .

[21]  Deborah Estrin,et al.  The Tenet architecture for tiered sensor networks , 2006, SenSys '06.

[22]  Divyakant Agrawal,et al.  Medians and beyond: new aggregation techniques for sensor networks , 2004, SenSys '04.

[23]  Sanjeev Khanna,et al.  Power-conserving computation of order-statistics over sensor networks , 2004, PODS.

[24]  Matt Welsh,et al.  Monitoring volcanic eruptions with a wireless sensor network , 2005, Proceeedings of the Second European Workshop on Wireless Sensor Networks, 2005..

[25]  Wei Hong,et al.  A macroscope in the redwoods , 2005, SenSys '05.

[26]  L J CHAMPNESS.  What is a line? , 1946, Radiography.

[27]  David E. Culler,et al.  Towards a Sensor Network Architecture: Lowering the Waistline , 2005, HotOS.

[28]  Yunhao Liu,et al.  Contour map matching for event detection in sensor networks , 2006, SIGMOD Conference.

[29]  Wei Hong,et al.  Beyond Average: Toward Sophisticated Sensing with Queries , 2003, IPSN.

[30]  J. Hershberger,et al.  Speeding Up the Douglas-Peucker Line-Simplification Algorithm , 1992 .

[31]  Urbashi Mitra,et al.  Boundary Estimation in Sensor Networks: Theory and Methods , 2003, IPSN.

[32]  John Anderson,et al.  Wireless sensor networks for habitat monitoring , 2002, WSNA '02.