WaldIS - a web-based reference data system for the ...

WaldIS - a web-based reference data system for the forests in Germany Christian ADEN, Lukas KLEPPIN, Gunther SCHMIDT and Winfried SCHRÖDER

The GI_Forum Program Committee accepted this paper as reviewed full paper.

Summary For the assessment of the forest condition in the Federal Republic of Germany the annual forest condition surveys (Waldzustandserhebung - WZE) are most important. The results of the evaluation are used for political decision making in terms of forest conservation. In annual reports on forest condition the results of the surveys were compiled by the Federal Research Centre for Forestry and Forest Products (Bundesforschungsanstalt für Forst- und Holzwirtschaft - BFH). Although there are other important forest monitoring programmes in Germany only the results of the WZE are considered for the report. The necessary compilation of forest data which are collected and stored separately by federal authorities can be accomplished easily by web based technologies. Not only the online completion of different forest survey databases will enhance the compilation process but also the linkage with data from various ecosystem compartments located on different servers up to spatial data infrastructures (SDI) is possible. This allows an ecological comprehensive cross-border view of the forest condition in the federal states of Germany and accelerates statistical analyses. In the framework of the project “Evaluation of hypotheses and development of a reference data system for the condition of forest ecosystems by means of long term data of the permanent forest observation” the web based GIS WaldIS is developed as a submission and reference data system based on open source software and international standards.

1

Background

Since 1984 the WZE is the most important survey for the appraisal of forest condition in the Federal Republic of Germany. Although – due to defoliation as the main indicator of forest condition – the scope and the soundness of these evaluations were impeached occasionally the monitoring program is well established. Undoubtedly, the canopy leafiness measured in percentage of defoliation is one characteristic trait for the evaluation of forest condition but not the only one: the slowly changing chemical characteristics of the soil which affects fine roots and subsequently the health of trees (Bauch et al.1985). Furthermore, the disturbance of the nutrient supply (Meiwes et al. 1999) and the deposition of air pollutants and climate conditions (Knabe et al. 1985) have to be considered as well. Forest decline is likely to be induced by a bunch of abiotic and biotic factors (Baule 1984; Schröder et al. 2007). Because of this the relationship between defoliation and other observed tree properties on the one hand and sampling site characteristics and deposition of air pollutants on the other hand were analysed with multivariate statistical methods since the middle of the 1980s. But

Ch. Aden, L. Kleppin, G. Schmidt and W. Schröder

methods like Classification and Regression Trees (CART) or Chi Square Automatic Interaction Detection (CHAID) helping with integrated analyses could not be established in German forest ecology (Riek & Wolff, 2000) even though the results are very easy to understand. For applying these methods it is important to have access to the forest monitoring data of several forest monitoring programmes. The particular monitoring programmes of the federal states like the WZE, the soil condition survey (Bodenzustandserhebung - BZE) or the evaluation of the foliar chemistry (Immssionsökologische Waldzustandserfassung - IWE) which are part of the Level I network located on the same plots for example in North Rhine-Westphalia as well as data of the Level II intensive monitoring network are not collected and analysed within one authority of the respective federal state due to different responsibilities. In North RhineWestphalia, for example, the data of the BZE and the IWE on the one hand and the data of the WZE on the other hand are collected by two different departments of the Federal State Authority for Nature, Environment and Consumer Protection (Landesamt für Natur-, Umwelt- und Verbraucherschutz - LANUV). Although both departments are using the same plots since 1988 integrated analyses were difficult in the past. The annual forest condition survey evaluates the tree condition, the forest stand and the plot in a 4 x 4 km or an 8 x 8 km raster. The most important parameter is the estimation of canopy leafiness as an indicator for tree vitality. Other data like those characterising the observation plot with respect to the altitude above sea level, climatic conditions, hydrology, or slope direction have not been considered simultaneously in the analyses yet. The foliar chemistry has been evaluated periodically every five years since 1983/84. The measurements include concentrations of macronutrients like calcium, potassium, magnesium, nitrogen, phosphorus, and sulphur in the leaves or needles and, by this, describe the nutritional condition of the trees. Additionally, the plot characteristics are described and the canopy leafiness is estimated. The soil properties were analysed in 1990/91 for the first time. The second survey (BZE II) should be finished in 2008. Physical and chemical soil properties describing the soil matrix and the soil hydrology were analysed within this survey. Data compilation and storage is managed centrally by the BFH. The Federal Institute for Geosciences and Natural Resources (Bundesanstalt für Geowissenschaften und Rohstoffe - BGR) and the Federal Environment Agency (Umweltbundesamt - UBA) perform chemical analyses of the soil samples (UBA 2007). The BZE II should be harmonised with other national and international monitoring programmes to allow integrated analyses. Some years ago a special programme was initiated in North Rhine-Westphalia to integrate data of the BZE, the IWE and the WZE. Additionally, the Level II data of the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP-Forest) should be integrated, analysed and visualised together with other data (Mellmann & Stinder 2005). However, the development of the software was stopped due to the refusal of some federal state authorities to integrate their data into this system. Now, compilation and analysis of the data is going to be performed by the BFH. The BFH prepares an MSAccess database and sends it to the state authorities which then integrate their data and return the completed database to the BFH.

WebGIS WaldIS

A more effective compilation and analysis of data can be realised by web-based techniques. Against this background, the Joint Research Centre (JRC) developed the Forest Focus Monitoring Database System (FFMDb). This system works on web-based servers and collects data of several monitoring programmes. The focus lies on surveys of the Level I programmes (BZW, WZE, and IWE) as well as on different data of the Level II programme, concerning vegetation patterns, deposition loads and related measurements. The National Focal Centres have to submit the data online by using web forms for the upload of data records. After checking the data in terms of conformity they get stored in a database and analysed by the JRC. Additionally, the JRC generates maps of the observed plots by using the UMN Mapserver (Forest Focus 2007, BFH 2007). It is important to compile as many data of the implemented forest monitoring programmes as possible and to analyse them all together by means of multivariate statistical methods which are easy to understand and allow for spatially differentiated assessments. The JRC tries to realise this issue. So far, there are many barriers for a comparable workflow in Germany considering data collection, storage and evaluation due to different administrative responsibilities and different ecosystem compartment being surveyed. A good example for a harmonised, cross-border monitoring programme is the UNECE moss monitoring. The moss monitoring in Germany is coordinated by the UBA. The survey is to detect heavy metal accumulations in mosses resulting from atmospheric deposition. Pesch et al. (2007) developed a web-based system for integrating measurements and metadata of the sampling sites by means of web forms. The monitoring data is stored in a spatial database and the plots are visualised in a map generated automatically by the UMN Mapserver. It is possible to review the data and display query results in maps generated by the WebGIS interface.

2

Objectives

According to section 12 paragraph 3 of the Federal Nature Conservation Act the federal states should support each other in terms of environmental monitoring and the efforts should be realised in mutual cooperation and coordination. However, due to different monitoring methods and data formats and the monitoring data gathered from different environmental compartments is not as harmonised as it should be, stored heterogeneously and often without metadata documentation (Schröder et al. 2002). The integration of consistent data and data base systems can be realised efficiently by using a WebGIS. In summary, a WebGIS is suitable for implementing geospatial data and data infrastructures. Thus, we consider WebGIS technology to develop the information platform WaldIS. Above all, the facilitation of measurement and metadata upload as well as the administration and visualisation of and the access to the data are both ambition and challenge of the project. On the other hand the query and the logical linkage of measured data, metadata and geodata of the different forest monitoring programmes completed and enriched with several additional environmental programmes is another important task of the project. A web-based administration tool in the way of a content management system (CMS) will be established to reduce the preliminary work in converting geodata or integrating databases of the federal states. Furthermore, tools for statistical analyses will be implemented that allow an

Ch. Aden, L. Kleppin, G. Schmidt and W. Schröder

integrated evaluation of data from different data sources provided by the federal and national authorities. Besides, data selection and exchange is as well an essential service of the WebGIS WaldIS. For the development of such a system the use of Open Source software is an appropriate solution. The source code of the software can be modified and adapted to the respective requirements. The standards of the Open Geospatial Consortium (OGC) in terms of open interfaces and services are considered when choosing the software components as well as when determining access to geodata, measurements and metadata of the monitoring surveys. Last but not least, the possibility to link the WebGIS WaldIS with national and European information networks originated in the EU directive INSPIRE1 (Bernard 2006) will be ensured. Storage, visualisation and GIS based analyses of the data are only one goal of research, the other aims at analysing forest monitoring data in comprehensively by using multivariate statistics in an objective and understandable way.

3

Software, standards and system structures

3.1 Open Source Software The Open Source Initiative2 (OSI) specifies the concept Open Source with several criteria (Williams 2002). The access to the source code has to be free without any constraints in terms of circulation of the software to third parties or certain users and the range of use. The licence does not allow the discrimination of anyone. The software mostly is available and downloadable via the internet, and modifications of the source code have to be transferred under the same terms of use. It is allowed to use parts of the source code in other free software products. It is allowed to use the term Open Source if the software is protected by one of the licence models of the OSI. The most commonly used licence of the Free Software Foundation is the GNU Public Licence. It is not allowed to demand money for the acquisition and the use of the software. This does not eliminate a demand for money for the installation or the user based modification of the software. Nowadays, Open Source is a good alternative to proprietary software but there is no warranty for reliability of the software. The use of Open Source software is not restricted to private persons, also business companies and public authorities are using Open Source software in all fields of information technology. Examples are operating systems for servers like Linux and server based software like http-servers3 or CMS and desktop software like GRASS GIS, JUMP or Open Office (Spath & Günther 2005). Contrary to that, proprietary software products are distributed with licences and copyrights. Very often the user has to pay licence fees every year. Sharing of the software mostly is forbidden and the source code is hidden because it is the revenue of the developers (Spath & Günther 2005).

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http://www.ec-gis.org/inspire http://www.opensource.org/licenses/gpl-license.php Webserver der Apache Foundation

WebGIS WaldIS

3.2 Standards The standards of the OGC constitute the base of interoperable networks for spatial data infrastructures and additional attribute data located anywhere in the world. They are designed by using ISO-, CEN- and other standards and considered for most of the GIS software (Korduan & Zehner 2008). The most important standards of the OGC define Open Web Services (OWS) which are interfaces for a standardised access to remotely located geodata (Müller & Augstein 2005). The client/server-model describes web services as operations which provide information in different formats (mime-types) (Peng & Tsou 2003). The client requests are handled by a server which returns a response with standardised contents to the client. The communication between client and server is achieved by HTTP-get/post-variables (Dreesmann 2004). At least a Web Map Service (WMS) is needed to allow geodata access. Another example for OWS is the Web Feature Service (WFS) which provides vector based geodata instead of raster data as given by WMS. The Catalogue Service (CS-W) allows management of metadata (Müller & Augstein 2005). The Simple Features Implementation Specifications (e.g., SQL) define interfaces which provide a transparent access to geodata in heterogeneous data publishing systems. Another, and for sure, interesting standard for WebGIS is the Web Processing Service (WPS) which allows the standardised use of online GIS functions, for example, within the Open Source software GRASS GIS.

3.3 System structure and functions The software components used for the WebGIS WaldIS are the Apache http-server with the database management system PostgreSQL including the PostGIS extension for administrating vector based spatial data (Korduan & Zehner 2008), the UMN Mapserver for the generation of raster maps and the WebGIS Client Suite Mapbender4 (Fig. 1). In addition a PHP environment and some necessary libraries (GEOS5, Proj46, and phpMapScript7) were implemented. The libraries are important for handling and converting of projections and PHP based operations on geodata.

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WhereGroup, Bonn http://geos.refractions.net http://remotesensing.org/proj http://www.maptools.org/php_mapscript/

Ch. Aden, L. Kleppin, G. Schmidt and W. Schröder

Fig. 1:

System architecture of the WebGIS WaldIS

For the visualisation of geodata the WebGIS Client Suite Mapbender was used as graphical user interface. This software meets the OGC standards and specifications on geodata handling, metadata formatting and queries on map contents. Furthermore, the software offers several tools for navigation within the maps and the integration of remote WMS and WFS. The WebGIS WaldIS allows users to design a web-based information system on geodata and measurement data derived from any monitoring programmes. It provides various tools for displaying measurements and additional geodata without any experience in programming languages, the configuration of mapfiles or the creation of input masks for the documentation of monitoring programmes. Authorised users have to work in a predetermined schema (Fig. 2).

Fig. 2:

Workflow of the WebGIS WaldIS

WebGIS WaldIS

If a user just wants to visualise geodata he has to log in, first. Then the user has to upload a set of geodata via the CMS which is stored in the database (vector data) or in a folder (one for every user) of the file system (raster data). When the upload is finished the user has to switch to the layer form where given geodata are inserted into a mapfile. It is possible to define links and to choose attributes of the dataset to be queried and displayed in the map. The attributes of vector data are shown automatically. Also links to WMS and WFS can be managed within this form. After managing layers the layout of each layer has to be defined in the class form. Names, colours, arithmetic expressions and symbols for each class used to visualise the geo features have to be set. The next step is the description of metadata for each layer stored in the database. The metadata form was designed with respect to the ISO core dataset for geodata (Kresse & Fadaie 2004) and can be queried or linked with related information platforms like Portal U8 considering the standards of the OGC. After layer definition the mapfile is written automatically by using the inserts of the web forms including query templates for the defined geodata attributes. Then a particular Mapbender interface can be selected for the individual layout of the WebGIS GUI. The WebGIS Client Suite uses its own database and all entries which are used for the visualisation of the data are written into this database. Via a hyperlink the user is able to watch his geodata and to query them. The user determines whether people have to log in into the system or if there is an open access. To use the WebGIS WaldIS for implemented monitoring programmes or future survey periods the system offers a module to create and edit data entry forms. A new data entry form could be created including those attributes that have to be observed during the survey. Additionally, the data type has to be defined (e.g., integer, float, string) to ensure further analyses. For metadata description the system considers three input formats (single choice, multiple choice and text insert). After this, the possible choices for each question have to be defined, too. After saving the submission form the user has to manage access by creating user accounts. The form as well includes an input field for coordinate entry to ensure spatial visualisation of the monitoring sites by the WebGIS Client Suite. The respective projection has to be determined before. For testing the WebGIS WaldIS submission forms for WZE, BZE, IWE and the Level II plots were created. The authorised users will be able to fill in the form with measurements collected in the field by using a PDA or at their local desktop in the office. All data entries are stored in a respective database. To allow data download after finishing the monitoring campaign a download area is implemented where geodata can be obtained as shapefiles and attribute data as tables (XLS-format). A metadata query for geodatasets is provided by using an interface enabling users to insert three different keywords and a category to find data they are looking for. Besides, the WebGIS offers some tools to analyse geodata and additional attributes by GIS functions like buffering, measuring distances and intersections. These functions are part of the PostGIS library (Mitchell 2005) and were implemented with help of the PHP-mapscript library. Only datasets stored on the local server can be analysed with these functions and not those linked from remote WMS and WFS. 8

http://www.kst.portalu.de

Ch. Aden, L. Kleppin, G. Schmidt and W. Schröder

The WebGIS WaldIS offers two different user interfaces: the administrator is authorised to manage projects by maps, geodata and data entry forms. ”Normal” users are allowed to display maps and query or download data for their personal needs via the WebGIS Client Suite (Fig. 3).

Fig. 3: Screenshots of the WebGIS WaldIS (left: Mapbender interface, right: Metadata query results) Exemplary geodata of the Level I programmes between 1988 and 2004 from North RhineWestphalia were integrated as well as data of different monitoring programmes concerning analyses on forest condition (Tab. 1). Tab. 1: Datasets of the WebGIS WaldIS Dataset or monitoring programme WZE (forest condition survey)

BZE (soil condition survey) IWE (foliar chemistry) Nature protection areas Flora-Fauna-Habitats Climate data (precipitation, temperature, sunshine duration, global radiation) Ecol. landscape classification for Germany (Schmidt) Natural landscape main units (Meynen et al.) UNECE-Moss Monitoring Phenology data (spruce, oak, beech, pine) Basic maps (borders of Germany, counties, communes, streets, rivers, cities) CORINE landcover

Monitoring periods or year of creation 1990/93, 2000/02/03/04 (spruce), 1985/99, 2000/02/03/04 (oak), 1985, 2000/02/03/04 (beech), 1990/99, 2000/02/03/04 (pine) 1990 1988/93/98 (spruce) 2005 2005 1961-1990 2002 1959/61 1990/95, 2000/05 1961-1990 2000

WebGIS WaldIS

4

Conclusions and Outlook

Environmental monitoring provides information on condition and development of several ecosystem compartments. The information is important for policy makers and resource managers for decision making. Using the standards of the OGC helps in compilation and integration of data from different sources. A WebGIS – especially WaldIS – is an information platform which enables users to plan, manage and evaluate monitoring programmes and to analyse and publish measured and evaluated data, metadata and geodata. In fact, there are open source products for writing Mapfiles like MapLab9 or Mapstorer10 but these applications have to be installed on a PC and contain neither the Mapbender software nor other Client Suites. This and the fact that these applications are only able to manage maps for the UMN Mapserver is a big disadvantage. Additionally, the user needs to know more about map services and data declaration. WaldIS makes it much easier to declare mapfiles, layers and classes by query templates and metadata. The harmonisation of data at a basic level by data entry forms helps in integrating and analysing geodata from different monitoring programmes. Moreover, linkage with remote WMS and WFS is possible as well as data download for further evaluations. The federal states and the BFH, particularly, profit by fast and efficient data access. On the other hand, WaldIS facilitates German authorities to accomplish legal report requirements (in context of the EUWater Framework Directive, for example). For environmental monitoring standardised systems could be become important tools to evaluate data in a more effective way and to react quickly on environmental changes or hazards as the EU directive INSPIRE aims at. The use of sophisticated GIS functions should be improved by the implementation of GRASS GIS which is one of the next steps of the development. With its help it is also possible to analyse raster data online by using the standards for Web Processing Services (WPS). Also a catalogue for the documentation of statistical methods should be implemented.

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