Setup of an Internet Accessible Database and Spatially Enabled Internet Applications for Water Resources Management B. Mueschen Friedrich-Schiller-University (FSU) Jena, Institute of Geography, Dept. for Geoinformatics, Hydrology and Modelling, Loebdergraben 32, D-07743 Jena, GERMANY –
[email protected] Abstract – To help saving the water resources and ecological values in the Tisza River basin, eastern Europe, an integrated hybrid, internet accessible database has been implemented within the EU project “The Tisza River Project - Real-life scale integrated catchment models for supporting water- and environmental management decisions”. A geodata server was established which enables the storage, processing and analysis of spatial data together with relational data. An interface for secure and fast online access to the geodata server has been developed which serves as a metadata entry and metadata query tool both for geodata and timeseries. Furthermore a spatially enabled Internet application was implemented using an open-source development environment that allows display of spatial data as well as queries on relational data and spatial data via the Internet. Keywords: database, geodata server, map server, water resources management 1.
INTRODUCTION
Tisza River is the largest tributary to the Danube River (basin size 157.200 km2) and is located almost exactly in the geographic centre of Europe. The unique riparian wetland ecosystem of the river basin has to be protected and revitalized because it is seriously affected by water pollution from both point and non-point sources including serious accidents like the catastrophic cyanide spill in 2000. Furthermore severe water shortages and excessive inundations as well as devastating floods - occurring in the same year at the same place in many cases - were destroying unique species of flora and fauna. Within the project “The Tisza River Project - Real-life scale integrated catchment models for supporting water- and environmental management decisions”, financed by the European Commission (contract No. EVK1-CT-2001-00099, http://www.tiszariver.com), 11 European partners from Hungary, Slovakia, Romania, Belgium, Germany, Austria, and United Kingdom are concerned with the solution of these problems by integrating modern techniques such as hydrological and hydrodynamic modelling, Geographic Information System (GIS), database, and remote sensing. The project started in January 2002 and will last three years in total. 2.
OBJECTIVES
The overall project objective is to help saving the water resources and ecological values by developing a “real-life” scale integrated catchment model system for supporting water and environmental management decisions.
For that purpose a central project database shall be established with the specific scientific and technological objectives as follows: generation of a unique international database of one of the largest river basins of Europe which will serve as central data source for modelling purposes, implementation of a platform for intensive exchange of data and information between countries sharing the catchment, and guarantee of flexible and time saving access to that database by developing and implementing interfaces for data visualization and retrieval. 3.
METHOD
The methodological approach for the establishment of the International Tisza Database (ITDB) comprises: examination of existing data bases with respect to homogeneity, correctness, and plausibility, setup of a geodata server for storage, processing and analysis of spatial data together with relational data, implementation of interfaces enabling the online access via Internet, and input of vector and raster GIS layers, timeseries and descriptional data into the project’s database. With respect to the project’s long-term objective to establish a really operative database, software license restrictions as well as costs for software purchase and maintenance have to be considered. 4.
PROGRESS OF WORK
A Setup of a Geodata Server The examination of existing databases resulted in the choice of a hybrid concept of a Database Management System (DBMS) which combines a relational data model with a DBMS extension for spatial data management. This extension transforms a Relational DBMS (RDBMS) into a so called geodata server which enables the storage, processing and analysis of spatial data together with relational data. For this purpose geographic data types are converted to relational data, which then can be handled like any other data type through a standard SQL (Structured Query Language) interface. This technology introduces geographic data types, geographic functions, spatial reference systems, spatial indexing, and particular geographic metadata management. Thus data attributes and geodata can be linked, queries of geometric attributes as well as spatial queries can be sent out, and spatial operators can be used.
An analysis of available commercial software that combines RDBMS and GIS extension (e.g. GEOTASK Server, Oracle Spatial, ESRI SDE, IBM DB2 Spatial Extender, IBM Informix Spatial DataBlade) revealed that: costs for software purchase range between 15000 € and 30000 € (dependent on the processor model); costs for software maintenance are another 15% of purchase costs per year; there exist license restrictions at least for software redistribution. Fortunately the development of open source software has advanced considerably in the last five years. In the meantime robust open source software is available that offers advantages over commercial software that are prerequisite to extend the lifetime of an application like the ITDB (Working Group on Libre Software, 2000): The availability of the source code as well as the right to modify it enables the unlimited tuning and improvement of a software product. This makes it also possible to port the code to new hardware, to adapt it to changing conditions, and to reach a detailed understanding of how the system works. The right to redistribute modifications and improvements to the code, and to reuse other open source code, permits all the advantages due to the modifiability of the software to be shared by large communities. In substance, the fact that redistribution rights cannot be revoked, and that they are universal, is what attracts a substantial crowd of developers to work around open source software projects. The right to use the software in any way, combined with redistribution rights, ensures (if the software is useful enough), a large population of users, which helps in turn to build up a market for support and customization of the software. Open source software can be purchased at low costs or is even free of charge. Consequently, the open source software PostgreSQL was established as RDBMS; it enables a structured data administration in a normalized data base scheme. The conceptual and physical data model were created according to the International Standards Organization Draft International Standard (ISO/DIS) 19115 for Geographic information – Metadata (ANZLIC - the spatial information council online, 2003). PostgreSQL uses a client/server model. A PostgreSQL session consists of the following cooperating processes (The PostgreSQL Global Development Group, 2003):
geographic objects to PostgreSQL relational database (Ramsey, 2003). PostGIS "spatially enables" the PostgreSQL server, allowing it to be used as a backend spatial database for GIS. PostGIS follows the OpenGIS "Simple Features Specification for SQL". Both packages are free of charge and can be downloaded from the Internet (e.g. http://www.postgresql.org/ and http://postgis. refractions.net/). B Implementation of Interfaces for Metadata Handling An interface for secure and fast online access to the geodata server has been developed entitled “Tisza Metadata Portal”. It serves as a metadata handling tool both for geodata (geographic data such as GIS layers, satellite data, etc. in vector/point or raster format) and timeseries (e.g. measurements taken at hydrometeorological stations during a fixed time period). The Tisza Metadata Portal offers two essential components for metadata handling: 1. Metadata entry tool to insert metadata into the geodata server: For each dataset core metadata elements must be provided via Internet according to the ISO/DIS 19115 for Geographic information – Metadata as follows: “what”: title and description of the data set; “when”: when the data set was created and the update cycle, if any; “who”: data set originator or creator and supplier; “where”: the geographical extent of the data set based on coordinates, geographical names or administrative areas; “how”: how to obtain more information about the data set, how to order the data set, available formats, access constraints etc. From the technical point of view, the user completes online html templates which are then transferred to the database by Java servlets. 2. Metadata query tool to search for existing metadata: Existing metadata can be scanned by search criteria, thus identifying a dataset with all given metainformation as indicated above.
A server process, which manages the database files, accepts connections to the database from client applications, and performs actions on the database on behalf of the clients.
C Implementation of an Interface for Internet Mapping MapServer software - originally developed by the University of Minnesota in cooperation with NASA and the Minnesota Department of Natural Resources - was installed as an open source development environment for building spatially enabled Internet applications (Regents of the University of Minnesota, 2003). MapServer can use PostGIS as a data source and does provide enough core functionality to support a wide variety of web applications: Beyond browsing GIS data, it allows to create geographic image maps, i.e. maps that can direct users to content.
The user's client (frontend) application to perform database operations, wheras client applications can be very diverse in nature: a client could be a text-oriented tool, a graphical application, a web server that accesses the database to display web pages, or a specialized database maintenance tool. Some client applications are supplied with the PostgreSQL distribution, most are developed by users. Further PostGIS software was implemented to add support for
MapServer generally runs as a Common Gateway Interface (CGI) application from the http server. As we can see in Fig. 1, the “Tisza River Information System” (TRIS) was developed as MapServer CGI application. TRIS uses the following resources: a http server like Apache or Internet Information Server; MapServer software; an initialization file that triggers the first view of the Map-
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Figure 1. Prototype of the Tisza River Information System (TRIS) as MapServer application.
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Server application; the initialization file is a regular html file and uses a form to send an initial query to the http server that returns a result from the MapServer. MapServer is stateless, and MapServer is started and executed each time a query is received, so this initialization file is just required to pass a variety of (hidden) parameters to the application (Regents of the University of Minnesota, 2003); a Mapfile that controls what MapServer does with the data, that defines the data to be used in an application and
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display and query parameters respectively. It also includes information about how to draw the map, the legend, and maps resulting from a query (Regents of the University of Minnesota, 2003); a template file that controls the MapServer application's user interface in the browser window; it controls how the maps and legends output from MapServer will appear on an html page; it operates like any other html file except that certain fields can be modified by the MapServer CGI. The template file allows the author to place the map and legend
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on the page, and determine what ways the user is allowed to interact with the mapserver application (i.e. browse, query, zoom, etc.). MapServer uses the template file and replaces keywords in the template file with information on its current state or the GIS dataset, to produce the html file that is sent to the browser (Regents of the University of Minnesota, 2003); a GIS dataset; MapServer uses ESRI shapefile format as its default vector file format. Raster data can come in several different formats, depending on how MapServer is compiled. By default, MapServer supports GeoTiff files and Tiff files with world files (Regents of the University of Minnesota, 2003). 5.
SUMMARY
A unique database of the Tisza River basin entitled “International Tisza Database (ITDB)” was generated as central data source for hydrological modelling purposes. It consists of a geodata server (PostgreSQL/PostGIS software) which enables the storage, processing and analysis of spatial data together with relational data. Flexible and time saving secure access to that geodata server is guaranteed by an interface for metadata entry and query.
Furthermore a MapServer application entitled “Tisza River Information System (TRIS)” was implemented using an opensource development environment that allows display of spatial data as well as queries on relational data and spatial data via the Internet. REFERENCES ANZLIC - the spatial information council online, 2003. Standards & protocols. http://www.anzlic.org.au/asdi/metaiso. htm Regents of the University of Minnesota, 2003. MapServer, Current Version 4.0. http://mapserver.gis.umn.edu/ Ramsey, P., 2003. PostGIS Manual. http://postgis.refractions. net/docs/ The PostgreSQL Global Development Group, 2003. PostgreSQL 7.3 Documentation. http://www.postgresql.org/docs/7.3/ static/index.html Working Group on Libre Software, 2000. Free Software/Open Source: Information Society Opportunities for Europe? Version 1.2 (work in progress). Open Resources Magazine, http:// eu.conecta.it/paper/paper.html
