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GIS WEB SERVICES AND SATELLITE IMAGING AS A FRAMEWORK FOR
ENVIRONMENTAL MONITORING: THE DESIGN AND IMPLEMENTATION OF A
VEGETATION INDICES CALCULATION TEST CASE
D. Kotzinos ^*, N. Chrysoulakis"
“ Computer Science Department, University of Crete, P.O. Box 2208 71110 Heraklio, Greece - kotzino@csd.uoc.gr
? Institute of Applied and Computational Mathematics, Foundation for Research and technology - Hellas, P.O. Box
1527, 71110 Heraklio, Greece — zedd2@iacm.forth.gr
KEY WORDS: Spatial Information Sciences, GIS, Internet/Web, Interoperability, Imagery, Satellite, Global-Environmental-
Databases
ABSTRACT:
GIS web services bring to the Geographic information arena the promise to deliver algorithmic implementations and data services to
the broader community, following a simple yet powerful 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. Moreover it minimizes the
network traffic, since data do not need to be transferred to the client in every step of the operation. 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 one or both of the already developed web services, leading to a services-chaining effect. Web services
can by nature be used by both web-based and desktop applications alike so, as part of this work, two small client applications are
developed — one web-based and one desktop. in order to showcase the applicability and availability of the framework. End users will
use the two already mentioned clients and consequently the final result, implementing as a side effect a user interface, since web
services provide only a programming interface.
1. INTRODUCTION
A great deal of progress has been made in Earth Observation
(EO) over the last years. This has been driven largely by the
realization that the observation of global climate processes
requires the type of spatial and temporal coverage only afforded
by satellite remote sensing. In spite of the real time accessibility
of EO data such as NOAA (National Oceanic and Atmospheric
Administration) images offered by ground receiving stations,
most potential users refrain from using them because either the
format of the raw data and the processing procedures are
complex, or already processed data offered by institutions or
companies are not always tailored to the exact needs of the end-
user. Web-based geospatial technology provides the means to
enhance the dissemination of satellite-derived information and
to assist potential users with the processing of raw satellite data.
In the field of environmental information science one should
take into account the number and diversity of the organizations
dealing with the production, storage and manipulation of
geographic related data. The volume of available geographic-
related environmental data is increasing rapidly, but technical
and semantic non-interoperability prevents easy sharing and
integration of geospatial information. The internet revolution,
through the use of internet GIS technologies (Kotzinos and
Prastacos, 2001) although expanded the possibilities, has added
*
Corresponding author.
one additional problem: large amounts of data need to be
moved among users and providers, so as to enable the first to
perform their designated tasks. Since geographic-related data
are usually large in size this exchange becomes more and more
difficult improvements in communication
technology.
despite the
The last two years a new paradigm has entered the computing
world and is changing the way all these issues are handled. This
new paradigm is web services, which are based on the use of
universally accepted standards and bring data and services
together and both of them closer to the end user. Web services
are trying to turn the web from a medium of simply accessing
information to one that will bring together data discovery, data
access and data processing along with information retrieval.
GIS web services are a more profound paradigm of web
services due to the diversity and size of both geographic data
and software, as mentioned earlier. Using the new paradigm
users will be able to access both looking only for the particular
service or data-set they need. They will not be concerned about
format, availability and price, since they will “pay” and access
only for what they ask for.
In this paper an effort has been made to design and describe a
framework of GIS web services tailored to the needs of the
