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INTRODUCION TO WEB GIS

WEB GIS is a modern aspect of geographic information system which operates over the internet or more likely Web GIS is a Geographic Information System distributed across a networked computer environment to integrate, disseminate, and communicate geographic information visually on the World Wide Web over the Internet.”  [Gillavry, 2000]
Maps on the web provide a new paradigm for how people everywhere access and use geographic information. We use GIS maps on our desktops , the web , tablets , and smartphones for a sophisticated range of activities to apply advanced geographic information . web GIS is a transformation of GIS that brings analytics to spatial data in away that wasn’t possible before .
Previously satial data had to be processed , modified , and extracted to answer a predetermined set of questions . now the is transformed into web maps or services that are mashed up with different layers into a web gis , which provides the flexibility to answer any possible question . the data is ready and waiting to dynamically answer questions . it no longer needs to be processed for each individual question . web GIS is a much more flexible and agile workflow . web GIS brings GIS into the hands of the people . it reduces the need to create custom applications , provides a platform for integrating GIS with other business systems , and enables cross-organizational collaboration . Web GIS allows organizations to properly manage all their geographic knowledge . At the heart of Web GIS is a mapcentric content management system .
Web GIS is a type of distributed information system , comprising at least a server and a client , where the server is a GIS server and the client is a web browser , desktop application , or mobile application . in its simplest form , web GIS can be define as any GIS that uses web technology to communicate between a server and a client .
Here are a few key clements essential to web GIS :
·         The server has a URL so that clients can find it on the web .
·         The client relies on HTTP specifications to send requests to server.
·         The server performs the requested GIS operations and sends responses to the client via HTTP.
The format of the response sent to the client can be in many formats , such as HTML , binary image , XML (extensible markup language ), or JSON (java script objects notation ).


AN ARCHITECTURE OF AN OVERALL WEBGIS SYSTEM

To identify subsystems of an overall WebGIS we started from a general assumption that
geoinformation related to some area (i.e. city) cannot be captured, stored and maintained in a single
organizational unit GIS. Some of this information can have mutual and public importance, so it
should be shared and be accessible over Web.
Suggested architecture relies on a client/server model. A subsystem that acts as a client that enables
access to geoinformation is a WebGIS portal, while the function of sharing (role of a server) is
realized by expanding traditional GISs with a WMS and a WFS Web interfaces (Web-enabled GIS).
Using of OGC WMS and WFS interfaces for building WebGIS systems can be also found in
(Korduan and Bill, 2004). Figure 1 illustrates interrelation between components that correspond to subsystems.

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