Sensor Web is a special type of web-centric information system for collecting, modeling, storing, retrieving, sharing, manipulating, analyzing, and visualizing information of sensors, sensor observations, and associated phenomena. A Sensor Web contains a group of distributed and heterogeneous sensors that interconnected by a communication fabric and sharing information through interoperable inter-faces. User is able to access and, where applicable, control the sensors via World Wide Web (WWW). With the presence of cheaper, miniature, faster, and smart in situ sensors, and the increasing availability of abundant fast computing devices, wireless and mobile network access, and autonomous and intelligent geospatial software agents, Sensor Web becomes clearly a technological trend. This new earth observation information system opens up a new avenue to fast assimilation of data from various sensors (both in-situ and remote) and to accurate analysis and informed decision makings.