Advances in sensor technology and distributed computing, coupled with the development of open standards that facilitate sensor/sensor network interoperability, are contributing to the emergence of a phenomenon known as the 'Sensor Web'. This phenomenon can be described as an advanced Spatial Data Infrastructure (SDI) in which different sensors and sensor networks are combined to create a sensor-rich feedback control paradigm.

Featuring an advanced and scalable architecture that supports numerous diverse and heterogeneous sensor types, a Sensor Web includes a range of sensors such as flood gauges, air pollution monitors, stress gauges on bridges, Webcams and satellite-borne Earth imaging devices.

It is anticipated that global sharing of information will lead to a special kind of synergism. A fully-realised Sensor Web will permit intelligent resource management by the web, and allow self-modifying behaviour based on environmental factors and internal web diagnostics.

TWO ASPECTS OF THE SENSOR WEB

Technical considerations: The Sensor Web should be based on sensor networking and interoperability driven by standards, protocols, interfaces and encodings. Harmonisation of standards for sensors, sensor network communications and geospatial information processing will allow interoperability at four levels: the sensor level, the knowledge level, the application level and the simulation level.

Extracting meaningful information from the Sensor Web: The Sensor Web must be able to answer user-defined queries about the state of the environment. If we are to make sense of the spatio-temporal behaviour of real-world objects we must be able to analyse the behaviour of real-world objects instead of simply mapping their spatial distribution.