Sharing spatial information

The sharing of spatial data has been actively developed in Finland for the last two decades. These efforts have aimed at improving methods of data collection and guidelines for visualisation, as well as data harmonisation and clarifying the division of responsibility through a variety of projects. The trend in recent years towards network-based spatial data infrastructure will open up new opportunities for more effective sharing of the data in the future.

Data content providers in the Web service environment are already finding that there is a clear need for agreeing on common practises and standards. This situation is creating conditions for the development of standards for service interfaces and some degree of regulatory intervention to meet the rising efficiency requirements for society at large. Some projects at the Finnish Geodetic Institute (FGI) are especially looking at ways of implementing standardised service interfaces.

The primary objective of projects related to data sharing has been to promote the readiness of key organisations in the spatial information sector for implementing spatial data content services. Data sharing efforts have been made by developing integrated services. Open source software standards have also been developed in support of implementing these services.

The European Union directive for enhancing the use of spatial data, 'INSPIRE', has been a major contributor towards the sharing of geographic information. One of the most important standards for mapping services is the Web Mab Service (WMS) interface specification developed by the Open Geospatial Consortium (OGC), which is an official ISO standard (ISO 19128:2005). The WMS service protocol standardises information for online mapping interfaces. The service's mission is to provide a visual representation of geographic data. The interface does not take a position on the form in which the map data for the service is stored. The best services are able to comply with the principles of the WMS interface if the material is not already rasterized, and the resulting images are generated on the fly during a query situation. This enables the requesting software to truly and freely choose the content wanted for the map and the visualisation method. WMS client software is being offered as a range of sophisticated Web browser-based implementations. Another important way of using WMS services comes in the form of commercial GIS software, offering the opportunity to search for maps from standards-based Web services. Another key standard is the Web Feature Service (WFS) Interface Standard developed by the OGC, which allows requests for geographic data in source form according to a standardised procedure. The WFS standard has also been published in the ISO process (ISO 19142:2010). Spatial data query detail cropping practices are defined in a separate standard, which is in parallel to the WFS standard (ISO 19143:2010). For spatial data content and location modelling, the Geography Markup Language (GML, published in the ISO standard (19136:2007)) is used for expressing geographic content.

Example national project aimed at promoting the sharing of spatial data

The following organisations participated in the project: the Finnish Geodetic Institute, the National Land Survey of Finland, the Finnish Meteorological Institute, the Finnish Maritime Administration, the Geological Survey of Finland, the Finnish Environment Institute, the City of Espoo, Lounaispaikka (a spatial data co-operation network for south-west Finland) and Sito Oy.

Materials used in the project:

National Land Survey of Finland

Raster location maps, elevation map (FGI's server)

Finnish Meteorological Institute

Satellite weather image

South-western location

Turku region and county environment maps

Institute of Marine Research

Chlorophyll situation map

Finnish Maritime Administration

Coastal map (FGI's server)

Geological Survey of Finland

Soil type map, bedrock map

The City of Espoo

Guide map

DigiRoad

Guide map (FGI's server)

Diagram of the project showing the overall service development

During the project, the Geodetic Institute has been responsible for implementing an integrated WMS service. It is based on the MapServer platform using the WMS/WFS-based software server GeoServer. The map service is achieved through an integrated service, where the data can be viewed according to a set of content themes. The service takes care of the necessary coordinate transformations and utilises DigiRoad data on road locations and the digital elevation model from the National Land Survey of Finland.

The project, has been tested in a number of open source WMS client libraries. The maps generated through the integrated service have been tested in the Google Earth application. From the project experience, it can be seen that free selection in the client environment is one of the benefits that standard interfaces bring to the service infrastructure.