A CLIENT/SERVER MAP VISUALIZATION COMPONENT FOR AN ENVIRONMENTAL INFORMATION 
SYSTEM BASED ON WWW 
J. Wiesel, W. Hagg A. Koschel, R. Kramer, R. Nikolai 
Institut für Photogrammetrie und Fernerkundung (IPF) Forschungszentrum Informatik (FZI) 
Universitat Karlsruhe Karlsruhe 
Germany Germany 
(wiesel,hagg) QGipf.bau-verm.uni-karlsruhe.de {koschel,kramer,nikolai} @fzi.de 
Commission Il, Working Group 2 
KEY WORDS: Environment, GIS, Database, Mapping, On.line 
ABSTRACT 
Since more than 6 years an integrated EIS has been developed in the State of Baden-Wuerttemberg, Germany, managed by 
the Ministry of Environmental Protection (UIS-Baden-Württemberg). As technologies im proved, the basic architecture of UIS 
has been revised from a somehow centralized to a distributed system based on the concept of services and objects. Services 
can be offered and used by various state agencies, which are all connected to a state wide inter-agency computer intranetwork 
(LVN). To improve the accessability to UIS by state officers and citizens World Wide Web (WWW) has been selected as the 
basic technology to move the user interface part to. Several projects had been set up recently to convert major components 
of UIS from proprietary solutions to WWW. One important service in this context is to visualize thematic maps and business 
graphics. A WWW-based solution has been developed as part of the GLOBUS- and WWW-UIS- Projects, financed by the 
Ministry. Vector and raster data are being visualized using a WWW browser (Mosaic, Netscape) with the possibility to select 
map layers, themes, colours and scale. Business graphics, like charts, histograms and graphs can be added to these maps by 
on line access to databases via WWW. The server side part of the system is based on a modified version of GRASS for map 
painting, layout and legends, while business graphics are rendered by GNUPLOT. A set of Gnuplot-Macros has been written to 
automatically scale and layout these graphs. A user session concept has been designed and integrated into the system, which 
allows for individual setup and management of private maps and data sets including work space management on a per user 
basis. To facilitate and accelerate CGl-script programming (CGl= Common Gateway Interface), we decided to use TCL instead 
of C or shell script programming. These components have been integrated into WWW-Server side CGI scripts, controlled by 
TCL (Tool Command Language) scripts for generating HTML-pages, including forms, selection boxes, radio buttons, sliders 
and other user interface components needed by the map painter. To facilitate the creation and modification of HTML-pages, 
a comprehensive TCL-library was developed, allowing to easily generate new pages without specific HTML-knowledge using 
simple TCL-function calls. The system has been installed in the Ministry's network and is being used in day to day work. 
consortium (http:/ /www.w3.org), with HTML 2.0 being the 
: : ; current version and 3.0 to be released at the end of the year 
Since more than 6 years an integrated, interagency EIS has 1996 
been developed in the State of Baden-Wuerttemberg, Ger- 
many, managed by the Ministry of Environmental Protec- 
tion (UIS-Baden-Württemberg) (Umweltministerium-Baden- 
Württemberg and McKinsey, 1990) (Hess and Schultze, several WWW facilities can be used: 
1995). It is used to document, supervise and manage data 
and processes relevant to the environment. Geodata are a fun- 
damental part of Environmental Information Systems (EIS). 
They are needed to visualize and model processes, measure- 
ment and management data. A major component of UIS is a 
subsystem for storing, integrating and analyzing spatial data. 
This system (RIPS) is currently based on proprietary GIS and 
commercial Data Base Software. 
1 INTRODUCTION 
The current HTML 2.0 specification allows to integrate text 
and raster graphics into a document. To build user interfaces 
e HTML 2.0 forms 
— radio buttons 
— scrolling lists 
— text input fields 
e clickable image maps 
e WWW-GIS interface 
2 THE WORLD WIDE WEB e dynamic map generation 
  
The World Wide Web (WWW) is a client/server based ar- 
chitecture (December and Randall, 1994) for distributing and 
accessing data on internets. It is based on the HTTP (Hy- 
pertext transfer protocol) and the HTML (Hypertext markup 
language) for describing documents. WWW has been de- 
veloped at CERN, Geneva as a tool to share documents on 
the HEPNET, but is now in widespread use. It gained a 
lot of popularity since the NCSA published the first graphical 
Web browser - NCSA Mosaic - running on all major com- 
puter platforms (Eager, 1994). HTML is a special dialect of 
SGML. The language specification is controlled by the W3- 
HTTP is a connectionless protocol. This means, every trans- 
action is atomic; there is nothing like a logon procedure or a 
user context, which is normally needed for access verification 
or user identification. 
3 ARCHITECTURE OF A WWW-BASED EIS 
In figure 1 we describe a UIS architecture using a services 
based view: Horizontally we divide the system into user ser- 
vices and system services. System level services provide kernel 
functionality, like data base access, geo data access and basic 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996