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Dr. Satyaprakash satya@GISdevelopment.net Somebody asked me one day, what is the future of GPS? Without thinking twice, I said, it will go back to where it belongs, i.e., into the realm of surveying! I do not know why this answer came to my mind instantaneously, but when I started pondering on it, this increasingly seemed to be the future. Let us look at this more closely to understand why. GPS owes its origin to the fact that mariners wanted to be able to locate themselves anywhere on the earth during troubled times, when everything else has failed. Slowly it became the only device through which the location could be obtained easily, quickly and accurately. The surveyors exploited these features to the extent that today they cannot think of their surveying toolbox without this device. However, miniaturisation of the GPS chipsets and in turn the receivers and antennas, made this a favourite choice of companies working in location based services. This was the time when there were not many choices of systems available, which could locate objects. However, with current developments, apart from GPS, there are now many other devices that could be used to obtain the location of objects, whether moving or stationary. The widespread deployment of intercommunicating devices and systems like mobiles, RFID tags, WiFi access points, traffic cameras and speed checking instruments have made locating an object, without the use of GPS, a much easier task than ever before. These networks of devices communicating with each other have been termed as "Wireless Sensor Network (WSN)". Wikipedia defines WSN as a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations." A sensor network (Fig-1) normally constitutes a wireless ad-hoc network, meaning that each sensor supports a multi-hop routing algorithm (several nodes may forward data packets to the base station).  Fig 1: Sensor Network (Credit: Wikipedia) The above concept when extended to several such networks and sensors, communicating with each other through the Internet (or "World Wide Web"), gives us the "Sensor Web". Wikipedia defines the Sensor Web as a type of sensor network or geographic information system (GIS) that is especially well suited for environmental monitoring and control. 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/IPlike 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 (Fig-2). The novelty of the Sensor Web architecture lies in the ability of the individual pieces to act and coordinate with each other as a whole. This immediately allows the system to be synchronous throughout, unlike many other networks. In addition, the individual pods of a Sensor Web are all of equal status and Sensor Web architecture does not require special gateways or routing to have each of the individual pieces communicate with one another or an end user. By definition, a Sensor Web is an autonomous, stand-alone, sensing entity that does not require the presence of the World Wide Web to function. 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) or SensorNet (Fig-2). 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 feeding into an OGC-type network. How is this Sensor Web going to be useful for the location based services companies or the users? For any kind of LBS, positional information is the key. Till today GPS is the sensor which is being used for locating the object and then there has to be some medium through which the location can be transmitted to a central location where this information can be utilised. There are cases where GPS does not work (underground, inside buildings etc.) and alternate method of locating the object has to be found. With sensor network, there is no such need. Also, in the case of location through GPS, the device has to be equipped with a GPS receiver. With Sensor network, in place, the existing device can be picked up by the network and the location of the object can be determined and sent through the available network. Today, there is a need for a dedicated network, either GSM/ CDMA or any other RF network, through which the data can be made available to the network/ base station. However, with the Sensor Web, the network is already in place through which the location can be transmitted to the Internet, to be used for different purposes. OGC has already made progress in this regard and is working on the initiative called "Sensor Web Enablement" (SWE) where the members are building a unique and revolutionary framework of open standards for exploiting Web-connected sensors and sensor systems of all types. SWE presents many opportunities for adding a real-time sensor dimension to the Internet and the Web. This has extraordinary significance for science, environmental monitoring, transportation management, public safety, facility security, disaster management, Supervisory Control And Data Acquisition (SCADA) operations of utilities, industrial controls, facilities management and many other domains of activity. The OGC voluntary consensus standards setting process coupled with strong international industry and government support in domains that depend on sensors will result in SWE specifications that will quickly become established in all application areas where such standards are of use (Ref: OGC White Paper - OGC® Sensor Web Enablement: Overview And High Level Architecture by Carl Reed, Mike Botts, George Percivall and John Davidson, 2006). The OGC initiative has already resulted in formulation of the OpenGIS Location Services (OpenLS) Implementation specifications that includes a Tracking Service that queries the position of wireless devices from an OpenLS tracking server over the web, using the OpenLS XML protocol. With the above developments, you actually would not need GPS for locating the object; there are many devices that can do the work for you. This would lead the GPS to remain where it actually belongs - to the surveyors - doing core surveying and helping them in geodesy.  Fig 2: Sensor Web (credit: OGC) Page 1 of 1
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