Web based GIS as a Central Tool of an Information System for Interdisciplinary Research Projects
Claus Mueckschel and Wolfgang Köhler Institute of Biometry and Population Genetics, University of Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
1 Introduction The SFB information system is based on Internet technology and is structured as distributed client/server- In heterogeneous working groups of interdisciplinary architecture. Data management in a closer sense is research projects a common data and information organized through the relational database management management forms the basis for integration and system (RDBMS) MySQL. The user interfaces access interconnectedness. Central data storage ensures the data via Apache and Perl or PHP scripts. The scripts consistent and efficient data management of the handle the data input and output, write notes, build different disciplines. The data management must be able record tables and thus are part of an expanded database to represent adequately the research objects which are management system. Structured metadata together with described by the data. Both timelines and spatial data the described data are collected via web forms. must be presented and processed in environmental research projects which work on the ecosystemic level. Geographic information systems (GIS) proved of value for this purpose.
In the DFG-Sonderforschungsbereich (SFB) 299, the Collaborative Research Center 299 (www.sfb299.de) of the German Research Foundation we implemented such web-based GIS successfully. These systems comprise at least two computers connected in a client/server- configuration. They communicate through Internet technology, exchange geodata and offer GIS functionality. In the simplest case Web-GIS- technologies utilize static maps linked with graphics and HTML. All functionality must be designed explicitly on the server side. Any common web browser Fig.1 Modular composition of the SFB information system may serve as the client. More complex systems are One central component of the information system is based on distributed multi-user GIS. Proprietary Typo3 (http://typo3.org/). This is a content management Desktop-GIS software usually allows direct access via framework based on PHP and MySQL and has a Internet protocols without the use of a web server. modular structure. Thus it is an appropriate completion
since the existing database structures in the SFB have Especially Open-GIS standards as “Web Map Service” been realized with LAMP systems (Linux, Apache, (WMS) or “Web Feature Service” (WFS) (OGC, 2007) MySQL, PHP/Perl) and different extensions. Significant are used in the development of Web-GIS-techniques. advantages of this Open Source model are quality, They facilitate the finding of highly portable solutions, scalability of the systems, high performance and which are mainly based on Open Source technologies. stability. In this project several Web-GIS-systems are currently Typo3 is composed of two areas. The visible website is developed, ranging from tools for the simple depiction called frontend. It is accessed via a normal web of maps to interactive connection of SFB-data with browser. The main part of the SFB 299 website is particular data of local users. accessible to the public. Typo3 supports the creation
and management of frontend users. Thus an intranet
service available to the co-workers operates as a project 2 The SFB 299 information system specific data and information platform with a bundle of features. On the intranet new publications can be Usually setting up an information system is less entered via structured browser based masks. afflicted with difficulties and challenges than its Furthermore SFB co-workers can input metadata which permanent maintenance. For this reason information describe the primary data via consistent web forms. It is systems are mostly open systems which consist of distinguished between meta information of documents, different components and services (cf. Fig. 1). geo- point and other data. The search function of the They offer a collection of comfortable query tools; meta database guarantees the clear listing of desired especially concerning topical, temporal, spatial or information, e.g. conditions of citation and use or context related aspects, whereas the query results can be creation methods of the scientific data in the SFB. In presented in different ways. addition the metadata contain a link to the primary data. The management of the frontend users, the website maintenance as well as the whole database administration takes place in the so called backend. The backend is accessed via a web browser as well. The access rights vary depending on the role and working area of the respective co-worker. To use the extensive, spatial data of the SFB 299, a Web-GIS component was integrated into the information system which is linked to from the intranet area.
3 Web-GIS-components
In the SFB nearly all datasets have got a spatial Fig.2 Schematical illustration of the Web-GIS-architecture dimension. Spatial trends or processes can only be verified and analysed with GIS compatible tools. The shown geodata infrastructure is classical Visualization of the different data layers – e.g. land use client/server-architecture. It consists of an Apache web data or climatic maps - is a first step of such analysis. server, the UMN MapServer (http://ms.gis.umn.edu), Integration of GIS functionality into the internet based the server side scripting language PHP, the object information systems offers the advantage of performing relational database management system PostgreSQL visualization or analysis without special software or (www.postgresql.org) including the spatial language software knowledge. The use of HTML and the extension PostGIS, the cartographic projections library graphical browser interface requires no special retrieval Proj.4 and the geoportal solution Mapbender language. The browser based query is processed on the (www.mapbender.org), which forms the graphical user server side and is specified by the system administrator interface (GUI) with its browser based desktop. in conjunction with the SFB co-workers. The UMN MapServer runs as CGI-program on the 3.1 Composition of the geodata infra structure Apache web server. It is robust, stable, fulfils the The core component of a Web-GIS capable geodata standards of the Open GIS Consortium and is under infrastructure (GDI) is a map server for the generation constant development through a large user community. of dynamic map contents. In the SFB 299 there are Its task is to generate the maps requested by users. PHP mainly two approaches. First there is the use of the function calls control the functionality of the UMN proprietary software ArcIMS of the ESRI company. Its MapServer, which are forwarded to the map server by advantage lies in a rather quick off the shelf setup and the dynamically loadable module PHP MapScript. The the system is ready for use straight away. The high server side language PHP performs the interpretation of scalability of the system permits for a growing number the PHP code as well as the connection to databases and of maps that can occur in the course of the project, networks. Its interpreter is not executed as CGI-program which can be accessed by many users at the same time. but runs as an Apache module. This leads to a better SFB development focuses on an Open Source based performance. The object relational database architecture. On one hand there is a comparatively PostgreSQL serves as data server. Its spatial language complex installation and the yet existing restrictions in extension PostGIS expands the database for terms of extensive GIS functionality; on the other hand geographical objects, supports common GIS analysis there are numerous advantages. Besides low costs, functions and permits spatial indexing of GIS objects. especially the readily available Open Source code has to Essential advantages of the system are the noncomplex be mentioned. This allows a producer independent import of data in the popular ESRI-Shape-File-Format adaptation of the system according to changing requests and the comfortable configuration of the database with in the course of the project. Also implementation of the help of the graphical interface pgAdmin III special functions and the creation of individual (www.pgadmin.org). To overlay geodata with different interfaces are not complex. Moreover, apart from a web reference systems in one map the coordinates have to be browser the clients need no special software. Fig. 2 converted on the fly. This functionality is offered by the shows a schematical overview of the Web-GIS- cartographic projections library Proj.4 and supported by components. the deployed database. The client suite Mapbender serves as graphical user interface of the Web-GIS. It provides customizable desktops (GUIs) for viewing, navigation and querying of OGC compatible services like WMS, WFS and WMC (web map context). In addition, the software contains different components for user management, access protection and catalogue services. Access to the interfaces, their inherent functionalities and services is restricted to registered users. They are created by the administrator and allocated to different user groups. The Open Source system Mapbender is programmed in PHP and 4 Conclusions JavaScript and can at anytime be adapted to project specific requirements. For the application development and the selection of suitable software the following points where crucial: 3.2 Functionalities of the Web-GIS-application openness, scalability, usability, support of OGC Basic functionalities of the Web-GIS include the pure compatible services, means for simple data analysis visualization of the base data in the form of topical map without having to know specific desktop-GI-systems or layers concerning land use data, political structures, a retrieval language in the background. nature reserves and geographic regions as well as The number of analysis tools in the information system physical geographic parameters like soil, relief and will be gradually extended following the research climate of the investigation area. Users can compose projects needs. An application of this kind cannot their individual maps by switching layers on or off. The substitute a desktop-GI-systems, but it offers the WMS-standard allows the implementation of topics, possibility to use the current data pool project wide. It background maps and satellite pictures of remote map can be seen as user friendly geodata information servers. Furthermore simple point queries are possible system. In particular it is meant to offer the non with regard to the attribute data of the geometry data. modeling sub projects simple tools for rapid data requests and analysis. Thus the developed Web-GIS- For better performance, extensive datasets are divided application supports the common data use and into map sections, which are stored separately in the interdisciplinary work. system. To get a quick overview of the existing data of a specific landscape section, a user friendly search function was implemented. You can zoom into a landscape section by drawing a bounding box over it. At the same time, all corresponding records are listed with their storage place in the file system. In addition, the correspondent link to the meta database is shown. To search the datasets for certain criteria, PHP and SQL based functions were integrated. They are based on the WFS standard and self programmed script adaptations. Consequently the desired objects can be selected by the logic combination of different themes and tables respectively. The selection follows the principle choice of topic (table) => choice of attributes (columns) => choice of criteria (conditions). With this kind of questioning the user needs no knowledge of the internal data structure or of a special retrieval language. He composes his queries with a few clicks on selection lists or drop down menus. The selected criteria are stored in variables of the PHP scripts and inserted into the predefined SQL statements. In doing so, data storage in a PostgreSQL-/ PostGIS- database supports the embedding of spatial functions like position relation or area calculation in the request. The calculated results are marked subsequently in the map.
Before the termination of a Web-GIS-session, the current map composition can be saved permanently, including the last map section, the embedded WMS services and their layers, the used coordinate system and further adjustments. After logging in again and loading of the respective session, the working process can be continued at the same point. This is realized by the support of the WMC specification in Mapbender. The services can be generated, stored and reloaded by all client applications with implemented WMC standard. Thus an exchange of WMC documents between the subproject members is ensured and the work can be continued by different users. WMC calls equal XML documents, which contain metadata of the mentioned session settings and resemble workspaces or projects of a desktop GIS.