Sensor Web

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A Sensor Web is a type of sensor network or geographic information system (GIS) that is especially well suited for environmental monitoring. [1] [2] [3] [4] The term describes a specific type of sensor network: an amorphous network of spatially distributed sensor platforms (pods) that wirelessly communicate with each other. This amorphous architecture is unique since it is both synchronous and router-free, making it distinct from the more typical TCP/IP-like network schemes. The architecture allows every pod to know what is going on with every other pod throughout the Sensor Web at each measurement cycle.

Contents

[edit] Definition

The term "Sensor Web" was first used by Kevin Delin of NASA in 1997,[1] the novelty of that architecture lies in the ability of the individual pieces to act and coordinate as a whole. Another feature of the NASA systems was their synchronous behaviour, which is also a desired feature of some other implementations. In addition, the individual pods/nodes are all hardware equivalent [2] and Delin's architecture does not require special gateways or routing to have each of the individual pieces communicate with one another or an end user. The definition of a Sensor Web is an autonomous, stand-alone, sensing entity - capable of interpreting and reacting to the data measured - that did not require the presence of the World Wide Web to function. [5] However, since a Sensor Web can be constructed as a "web of webs", it also encompassed having individual Sensor Webs communicating with each other via the World Wide Web.[6]

A Sensor Web pod is merely a physical platform for a sensor and thus can be orbital or terrestrial, fixed or mobile and might even have real time accessibility via the Internet. Pod-to-pod communication is both omni-directional and bi-directional where each pod sends out collected data to every other pod in the network. As a result, on-the-fly data fusion, such as false positive identification and plume tracking, can occur within the Sensor Web itself and the system subsequently reacts as a coordinated, collective whole to the incoming data stream. For example, instead of having uncoordinated smoke detectors, a Sensor Web can react as a single, spatially-dispersed, fire locator.

The term "Sensor Web" is sometimes used to refer to sensors connected to the Internet or World Wide Web. Such terms are occasionally used in conjunction with projects of the Open Geospatial Consortium (OGC). In this case, the network architecture requires the Internet to link together the individual sensing elements. The OGC architecture is very different than that of a true Sensor Web system and requires schemes to bring together vastly different datasets, in the same way that TCP/IP is used to tie together vastly different pieces of hardware and computing platforms. Note also that a single Sensor Web may be an individual sensing element inputting into an OGC-type network.

Some developments have a goal of allowing people to "publish" their sensor network data in such a way that other people's search and analysis systems can automatically find the information.

[edit] Fielded Applications

Sensor Webs have been deployed that have spanned miles and run continuously for years.[7] Sensor Webs have been fielded in harsh environments (including deserts, mountain snowpacks, and Antarctica)[8] for the purposes of environmental science and have also proved valuable in urban search and rescue and infrastructure protection. [9]

The technology is not only monitoring the environment but sometimes also controlling the environment by actuating devices.[10]

[edit] Pods

A sensor web is made of a certain number of pods. Each pod usually contains[3]:

  • one or more sensor leading to one or more data channel,
  • a processing unit such as a micro-controller or microprocessor,
  • a two-way communication component such as a radio and antenna (radio ranges are typically limited by government spectrum requirements; unlicensed bands will allow for communication of a few hundred yards in unobstructed areas, although line of site is not a requirement),
  • an energy source such as a battery coupled with a solar cell,
  • a package to protect components against sometimes harsh environment,

Each pod also typically requires a support such as a pole or tripod[11].

[edit] Special Pod Functions

In Delin's definition, all pods in a Sensor Web are equivalent in hardware (there are no special "gateway" or "slave" pods). Nevertheless, there are additional functions that pods can perform besides participating in the general Sensor Web function.

Any pod of a Sensor Web can be a portal pod and provides users access to the Sensor Web (both input and output).[12] Access can be provided by RF modem, cell phone connections, laptop connections, or even an Internet Server. In some cases, a pod will have an attached removable memory unit (such as a USB stick or a laptop) that stores collected data.[13] [11]

The term of mother pod refers to the pod that contains the master clock of the synchronous Sensor Web system. The mother pod has no special hardware associated with it, its designation as a mother is merely based on the ID number associated with the pod.[14] Often the mother pod serves as a primary portal point to the Internet, but this is done only for deployment convenience. Early papers referenced the mother pod as "a prime node" if it additionally contained special hardware for a particular type of input/output device (say an RF modem).

Because of the inherent hopping of data within a Sensor Web, a pod with no attached sensors can be deployed as a relay with the single purpose of facilitating communication between the other pods and to expand the communication range to a particular end-point (such as a mother pod).[11] Sensors can be attached to relay pods at a later time and relays can also serve as portal pods.

[edit] Characteristics of a Sensor Web

The number of pods may vary, with examples of Sensor Webs with 12 to 30 pods.[15]

The shape of a Sensor Web may impact its usefulness, for instance a particular deployment[11] made sure each pod was in range to communicate with at least two other pods.

Sensor Web measurement cycles have typically been between 30 seconds and 15 minutes for deployed systems thus far. [16]

[edit] External links

  • SensorWare Systems, Inc. — A company spun-out of the NASA Sensor Webs Project and providing Sensor Web technology especially for agricultural, life safety, and remediation needs. Live, real-time streaming data from deployed systems may also be found on this site.
  • Sensor Web Alliance — An organization that is developing a collaborative research platform called the Sensor Web Alliance (SWA). The aim is to pool resources in the SWA, coordinate research and allow participating organisations to share IP, which will spread risk and lower the cost of entry.
  • SenseWeb Project — A Microsoft Research project that lets users visualize and query real-time data using a geographical interface such as Windows Live Local and allows data owners to easily publish their live data using a web service interface.
  • GeoSensor Web Lab, University of Calgary — A university research lab that is developing a GIS infrastructure for the Sensor Web and its applications. Several Sensor Web applications have been developed and deployed for environmental and agricultural applications. Project information, publications, and demo videos can be found on this site.
  • 52°North — An open partnership organization that interoperable web services and data encoding models, which constitute the technical building blocks of Spatial Data Infrastructures (SDIs).
  • OGC SWE — Since 2002, the Open Geospatial Consortium (OGC) has had a focused Sensor Web Enablement (SWE) activity. From the OGC perspective, a Sensor Web refers to web accessible sensor networks and archived sensor data that can be discovered and accessed using standard protocols and application program interfaces (APIs). In essence the OGC represents a "world wide web" of sensors.
  • Open SensorWeb Architecture Project - The project focuses on the development of service-oriented middleware for SensorWeb that integrates sensor networks and distributed computing environements such as computational Grids.
  • SensorWeb Research Lab - A university research lab that is developing Sensor Web systems and applying this revolutionary technology to critical scientific and social applications. One major sensor web project is to develop a prototype dynamic and scalable hazard monitoring sensor-web and apply it to volcano monitoring. The combined Optimized Autonomous Space - In-situ Sensor-web (OASIS) will have two-way communication capability between ground and space assets, use both space and ground data for optimal allocation of limited power and bandwidth resources on the ground, and use smart management of competing demands for limited space assets. The project is supported by NASA, involving Washington State University, NASA Jet Propulsion Laboratory and USGS Cascades Volcano Observatory.
  • SEPS Project - The Self-adaptive Earth Predictive System (SEPS) concept combines Earth System Models (ESM) and Earth Observations (EO) into one system through standard Web services. This is a collaborative project that consists of scientists from the Center for Spatial Information Science and Systems (CSISS) of George Mason University, NASA GSFC, and UMBC.
  • Semantic Sensor Web - The SSW project is an attempt to annotate sensor data with semantic metadata to provide contextual information essential for situational awareness. In particular, it is an approach to annotating sensor data with spatial, temporal, and thematic semantic metadata. This technique builds on current standardization efforts within the W3C and Open Geospatial Consortium (OGC) and extends them with semantic Web technologies to provide enhanced descriptions and access to sensor data. This project involves a team of scientists from the Knoesis Center at Wright State University.

[edit] Further reading

  • Sensor Webs, K.A. Delin, S.P. Jackson, and R.R. Some NASA Tech Briefs 1999, 23, 90 [1] open access publication.
  • The Sensor Web: Distributed Sensing for Collective Action, Kevin A. Delin Sensors Online July 2006, 18 [2] open access publication.
  • The Sensor Web: A Distributed, Wireless Monitoring System, Kevin A. Delin Sensors Online April 2004, 21 [3] open access publication.
  • Environmental Studies with the Sensor Web: Principles and Practice, Kevin A. Delin, Shannon P. Jackson, David W. Johnson, Scott C. Burleigh, Richard R.Woodrow, J. Michael McAuley, James M. Dohm, Felipe Ip, Ty P.A. Ferré, Dale F. Rucker, Victor R. Baker Sensors 2005, 5, 103-117 [4] open access publication.
  • OGC Sensor Web Enablement: Overview and High Level Architecture, Botts, Percivall, Reed, and Davidson [5] OGC White Paper, July 2006 open access publication.
  • Open Sensor Web Architecture: Core Services,Xingchen Chu, Tom Kobialka, Bohdan Durnota, and Rajkumar Buyya, Proceedings of the 4th International Conference on Intelligent Sensing and Information Processing (ICISIP 2006,IEEE Press, Piscataway, New Jersey, USA, ISBN 1-4244-0611-0, 98-103pp), Dec. 15-18, 2006, Bangalore, India. [6] open access publication.
  • A SensorWeb Middleware with Stateful Services for Heterogeneous Sensor Networks,Tom Kobialka, Rajkumar Buyya, Christopher Leckie, and Rao Kotagiri, Proceedings of the 3rd International Conference on Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP 2007, IEEE Press, Piscataway, New Jersey, USA), Dec. 3-6, 2007, Melbourne, Australia. [7] open access publication.

[edit] References

  1. ^ a b Botts, Mike; Alex Robin (Oct. 2007). "Bringing the Sensor Web Together". Geosciences. pp. 46-53. http://www.brgm.fr/dcenewsFile?ID=473. 
  2. ^ a b Delin, Kevin; Shannon Jackson (2000). "Sensor Web for In Situ Exploration of Gaseous Biosignatures". IEEE Aerospace Conference. http://www.sensorwaresystems.com/historical/resources/sensorweb-concept.pdf. 
  3. ^ a b Delin, Kevin (2005). "Sensor Webs in the Wild". Wireless Sensor Networks: A Systems Perspective. Artech House. http://www.sensorwaresystems.com/historical/resources/DelinSensorWebsInTheWildChapter2005.pdf. 
  4. ^ Torres-Martinez, Eduardo; Granville Paules; Mark Schoeberl; Mike Kalb (August-November 2003). "A Web of Sensors: Enabling the Earth Science Vision". Acta Astronautica, Volume 53, Issues 4-10. pp. 423-428. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1N-4B1RG8C-M&_user=2429682&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000057245&_version=1&_urlVersion=0&_userid=2429682&md5=c0905e74c5d714f456b4dbd9d7105f05. 
  5. ^ Delin, Kevin; Shannon Jackson (2001). "The Sensor Web: A New Instrument Concept". SPIE's Symposium on Integrated Optics. http://www.sensorwaresystems.com/historical/resources/sensorweb-concept.pdf. 
  6. ^ Delin, Kevin (2002). "The Sensor Web: A Macro-Instrument for Coordinated Sensing". Sensors, Volume 2. pp. 270-285. http://www.mdpi.net/sensors/papers/s20700270.pdf. 
  7. ^ http://www.sensorsmag.com/sensors/article/articleDetail.jsp?id=358630
  8. ^ http://www.sensorsmag.com/sensors/article/articleDetail.jsp?id=328918
  9. ^ Delin, Kevin; Edward Small (2009). "The Sensor Web: Advanced Technology for Situational Awareness". Wiley Handbook of Science and Technology for Homeland Security. John Wiley & Sons. http://www.sensorwaresystems.com/historical/resources/SensorWareSystems-SituationalAwareness-Handbook.pdf. 
  10. ^ http://www.sensorwaresystems.com/historical/press/RFIDJrnl_NASA_Oct04.pdf
  11. ^ a b c d http://www.sensorwaresystems.com/historical/resources/Delin_et_al_Antarctica_2003.pdf
  12. ^ http://www.sensorwaresystems.com/historical/press/RFIDJrnl_NASA_Oct04.pdf
  13. ^ http://www.sensorsmag.com/sensors/article/articleDetail.jsp?id=358630&sk=&date=&pageID=2
  14. ^ http://www.sensorsmag.com/sensors/article/articleDetail.jsp?id=358630
  15. ^ http://www.sensorwaresystems.com/historical/press/RFIDJrnl_NASA_Oct04.pdf
  16. ^ http://www.sensorwaresystems.com/historical/resources/huntington_sw5.shtml
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