THE DEVELOPMENT OF A PROTOTYPE GEOSPATIAL WEB SERVICE SYSTEM 
FOR REMOTE SENSING DATA 
Meixia Deng * *, Peisheng Zhao*, Yang Liu?*, Aijun Chen? Liping Di* 
* George Mason University, Laboratory for Advanced Information Technology and Standards - (mdeng, pzhao, yliu$, 
achen6, ldi)@gmu.edu 
KEY WORDS: development, remote sensing, data, geospatial, Web service, information 
ABSTRACT: 
Recent progress on Web service technology may provide a solution to current problems in using remote sensing data. This paper 
presents a prototype geospatial Web service system to demonstrate the advantages of such a system over the traditional non 
service- based systems for reducing the difficulty of using remote sensing data for research and applications. The foundations of the 
prototype system are the OGC and W3C standards that define the interfaces for accessing geospatial data and the methods for 
constructing chainable geospatial Web services. In the system, we have implemented a limited number of interoperable services, 
including WCSportal, reprojection, visualization, classification, reformatting, subsetting, and georectification. The system allows 
users to dynamically chain the services with other services and services with data to produce the user-specified products over the 
Web. The successful implementation of this prototype system will provide us experience in for building large, operational Web 
systems for geospatial information and knowledge services. 
1. INTRODUCTION 
1.1 W3C and OGC Web Services Standards 
Web technologies have developed significantly. from their early 
days of being used only to provide an interface for distributed 
services with HTML forms calling from COGI scripts to the point 
where now XML based environments have enabled Web 
services. 
The World Wide Web Consortium (W3C), created in October 
1994, is an open, international organization with the goal of 
leading the World Wide Web to its full potential by developing 
common protocols that promote its evolution and ensure its 
interoperability. W3C activities are generally organized into 
groups. The Working Groups in W3C are in charge of technical 
developments. Web services activity in W3C currently consist 
of four major working groups: XML Protocol Working Group, 
Web Services Description Working Group, Web Services 
Architecture Working Group and Web Services Choreography 
Working Group [http://www.w3.org/2002/ws/]. These working 
groups develop the technical standards for Web services 
application, produce the documents used for Web services such 
as XML protocol , SOAP version 1.2, WSDL version 2.0, Web 
services architecture and choreography. 
The Open GIS Consortium, Inc. (OGC) is a member-driven, 
non-profit international trade association that is leading the 
development of geoprocessing interoperability computing 
standards. Within the broader context of Web Services, OGC 
Web Services (OWS) represent an evolutionary, standards- 
based framework that enables seamless integration of a variety 
of online geoprocessing and location services [OGC 
Interoperability Program White Paper, 2001]. OGC develops 
standards in the context of OWS. OGC is the only international 
organization dedicating to develop geospatial implementation 
* Corresponding author. 
LD 
standards based on ISO, FGDC, INCITS, W3C, and other 
organizations’ content standards. 
W3C and OGC Web services standards are the foundation to 
implement our geospatial Web services and build our prototype 
geospatial Web service system for remote sensing data. 
1.2 Web Services and Geospatial Web Services 
What is a Web service? There are many definitions from 
different communities. The W3C Web services architecture 
working group gives the definition as the following: 
A Web service is a software system designed to support 
interoperable machine-to-machine interaction over a network. It 
has an interface described in a machine-processable format 
(specifically WSDL). Other systems interact with the Web 
service in a manner prescribed by its description using SOAP 
messages, typically conveyed using HTTP with an XML 
serialization in conjunction with other Web-related standards 
[W3C note 2004 ]. 
As stated above, a machine-processable format WSDL plays a 
key role in describing a Web service. WSDL is the abbreviation 
for Web Service Description Language, an XML language for 
describing Web services. The W3C Web Service Description 
Working Group published their working draft WSDL version 
2.0 on March 26, 2004 [W3C WD 2004]. WSDL is the 
standard language used to describe all Web services by both 
W3C and OGC. 
In short, we can define a Web service as a program that 
performs a defined action and that can be found, invoked, and 
executed over the Web. Then it is quite straightforward for us to 
define a geospatial Web service. A geospatial Web service is a 
Web service which performs an action on geospatial data or 
Internat 
informa 
from V 
characte 
Geospat 
(e.g. ge 
from the 
many w 
type ins 
data are 
much m 
data. Us 
expert k 
to prepr 
archived 
format t 
these d 
research 
Geospat 
quite d 
example 
very co 
general | 
Service « 
Web ser 
1.3 M 
The im] 
service 
instead « 
sensing 
terabyte 
valuable 
econom; 
only ava 
expert | 
process 
limits r 
commun 
knowled 
informat 
sometim 
incident 
data ist 
À gcosp 
Web tec 
services 
user-spe 
for those 
Web se 
advantag 
reducing 
and appl 
To desig 
major co 
F 
e bo 
>