Due to financial or administrative constraints, access to official spatial base data is currently limited to a small subset of all potential users in the field of spatial planning and research. This increases the usefulness of Volunteered Geographic Information (VGI), in particular OpenStreetMap (OSM), as supplementary datasets or, in some cases, alternative sources of primary data. In contrast to the OSM street network, which has already been thoroughly investigated and found to be practically complete in many areas, the degree of completeness of OSM data on buildings is still unclear. In this paper we describe methods to analyze building completeness and apply these to various test areas in Germany. Official data from national mapping and cadastral agencies is used as a basis for comparison. The results show that unit-based completeness measurements (e.g., total number or area of buildings) are highly sensitive to disparities in modeling between official data and VGI. Therefore, we recommend object-based methods to study the completeness of OSM building footprint data. An analysis from November 2011 in Germany indicated a completeness of 25% in the federal states of North Rhine-Westphalia and 15% in Saxony. Although further analyses from 2012 confirm that data completeness in Saxony has risen to 23%, the rate of new data input was slowing in the year 2012.

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Routing and navigation web services are becoming widely used, and make use of both commercial and VGI datasets. It is now becoming widely acknowledged that a 'one fits all' method of generating and presenting routes is not applicable. In particular, the accessibility of places for the mobility impaired has become a key focus with several services addressing topics such as how accessible locations of interest are and how to best generate routes for people who need to consider additional factors. Though datasources such as OpenStreetMap (OSM) are well suited for such topics, several issues including the quality of the underlying data remain. Through the use of quality assessment tools it is possible to identify areas with inadequate data completeness with regards to the information needed for the mobility impaired and thus encourage the enrichment of these areas through specialised tagging applications. Such data can then be used in routing and navigation services which focus on ensuring that routes being generated and presented fit the personal requirements of the traveller.

Finding the shortest path through open spaces is a well-known challenge for pedestrian routing engines. A common solution is routing on the open space boundary, which causes in most cases an unnecessarily long route. A possible alternative is to create a subgraph within the open space. This paper assesses this approach and investigates its implications for routing engines. A number of algorithms (Grid, Spider-Grid, Visibility, Delaunay, Voronoi, Skeleton) have been evaluated by four different criteria: (i) Number of additional created graph edges, (ii) additional graph creation time, (iii) route computation time, (iv) routing quality. We show that each algorithm has advantages and disadvantages depending on the use case. We identify the algorithms Visibility with a reduced number of edges in the subgraph and Spider-Grid with a large grid size to be a good compromise in many scenarios. ARTICLE HISTORY