DESIGN OF GIS WEB SERVICES FOR ENVIRONMENTAL MONITORING : USING SATELLITE IMAGING TO CALCULATE VEGETATION INDICES

The recent developments in the field of computing are providing us with a new computing paradigm, the web services paradigm. Under this paradigm, a solution to a problem is sought by providing individual services that can be used either in combination or standalone, as part of a greater application to solve the bigger problem. The main advantage is that the service can be used remotely without the user’s actual knowledge and intervention and by multiple users at the same time, eliminating the need for constant updates to locally installed software. This overall framework is currently being developed and tested and the one major test application presented is the development as a web service of an algorithm that calculates vegetation indices using low spatial resolution satellite images. To achieve the overall result two separate web services are developed: a) One handling the acquisition and manipulation of the satellite images being used. A low-resolution satellite ground receiving station is used to provide real time satellite data. b) A second one implementing a vegetation index calculation algorithm, using results form the first web service. It’s worth noting here that the system has the potential to be expanded by more algorithms (e.g. for surface temperature estimation, for aerosol spatial distribution monitoring, for perceptible water calculation) that will still use the image manipulation web service. It is also important that the web services can by nature be used by both web-based and desktop applications and can easily be integrated in and used by other independent applications. Finally, two small client applications are being developed which will use the two already mentioned web services and present the user with the final result, since the web services provide only a programming interface and not a user one. The web services developed follow the Open GIS Consortium (OGC) specifications.