Web services for thematic maps

Abstract

The current world of information technologies (including geoinformation technologies/GIT/ as well as internet maps) heads towards the new generation of Web (as a collection of interlinked documents accessed via the Internet). The next development stages of Web (Web 2.0, Web 3.0, Semantic Web etc.) are associated with terms – user-centred applications, information sharing, collaborative work and interoperability. Just the last word is very important because it represents the necessary condition to functioning of complete system and its components like blogs, wikis, mushups, web applications and services. Geoinformation technologies work also with one important term associated with Web – Spatial Data Infrastructures (SDI). The chapter “Web Services for Thematic Maps” is divided into two main parts. The first part (sub-chapters 10.2-10.5) is focused on common questions of thematic cartography and application of web services in cartography. There are also mentioned problems associated with web services in cartography like spatial data heterogeneity, standardisation or lack of semantics. Because this theme is very large, we have selected web services standardized by Open Geospatial Consortium (OGC) and thematic maps as the important representatives of both domains. This part describes general service-oriented architecture and four main OGC web services, including their advantages, disadvantages and “cartographic” abilities. The second section (10.6, 10.7) of this text is centred on a design of application of Web Processing Service (WPS) to thematic cartography. We describe current implementations of WPS (e.g., project Humboldt or open-source solution PyWPS). The main part is focused on the concrete application of WPS to generating of different types of thematic maps in the format SVG (Scalable Vector Graphics). The general principle of the generating of SVG maps through XSLT (Extensible Stylesheet Language Transformation) as desktop solution was used in the project VisualHealth and it was published in various papers in the past years (Chile 2009, Austria 2009, Czech Republic 2009, Bulgaria 2008, Moscow 2007). This text describes a combination of existing desktop solution and WPS. The aim is the using XSLT processor, pre-defined XSLT styles intended for transformation of spatial data to SVG format, and RELAX NG (REgular LAnguage for XML Next Generation) scheme (the method of description of a maps and their attributes) as web application.