## 2 Literature Overview  
Currently there is only a small body of literature published on analysis of the spatial data contents of the OSM database. However these publications have delivered important contributions on many issues related to OSM in general. In classical GIS methodologies there have been several accuracy and ground-truth comparisons of OSM data with authoritative sources of spatial data. These include [PERSON] [15] with the Ordnance Survey UK, [PERSON] and [PERSON] [16] compared OSM data with Teleatlas Data in Germany, [PERSON] and [PERSON] [17] with the French OS dataset IGN), and [PERSON] _et al_. [18] with land cover features in Ordnance Survey Ireland datasets. In terms of using OSM as a primary source of geographic information there are several examples in the literature. [PERSON] and [PERSON] [19] present an extensive 3D building ontology based on OSM making it possible to map indoor spaces in addition to the outdoor environment. The richness of spatial data for urban areas in VGI, particularly for buildings, has seen some authors (such as [PERSON] and [PERSON] ([20]) use VGI for the creation of 3D building models for the purposes of building virtual city models. [PERSON] _et al_. [8] also discuss the generation of 3D models. [PERSON] _et al_. [4] present a framework for distribution of environmental information using OSM. Some work has been presented on the motivations of those volunteers who contribute to VGI projects [9, 21]. Finally some authors have investigated the development of applications based upon the local spatial knowledge inherent in VGI. [PERSON] _et al_. [22] develop software for wildfire evacuation modelling and travel scenarios of urban environments using VGI as an input data source. [PERSON] _et al_. [12] argues that local knowledge demonstrated in VGI (coupled with the enthusiasm and dedication of contributors as emphasized by [PERSON] [23]) could potentially be very rich extending to the point \"where there is reason to consider engaging local expertise in the production and updating of NMA topographic maps\". The issue of the spatial data quality in OSM is dominant amongst the available literature. [PERSON] [23] argues that in the case of OSM the rather unique task of compiling independently contributed pieces of a (geographic) patchwork necessarily imposes some degree of quality control. He adds that \"one might term this process structured, to distinguish it from the essentially unstructured process by which entries in Wikimapia and other VGI gazetteers are compiled\". The quality of VGI is now a hot-topic in GIS [18]. [PERSON] _et al_. [24] argue that in VGI \"since general users can add and change data, the stored data should be updated frequently, resulting in an abundant and updated geographic dataset\". This has \"reversed the traditional top-down flow of information\" [25]. [PERSON] _et al_. [24] conclude by arguing that one of the most serious disadvantages of OSM is that the underlying data is acquired by non-professionals with non-professional equipment, meaning that there is no guarantee of quality about the data unless it can be compared to some other source. [PERSON] and [PERSON] [26] argue that as the amount of VGI continues to grow \"the issues of credibility and quality should assume a prominent place on the research agenda\". This will require a multi-disciplinary approach combining knowledge from geography, computer science, social sciences, to understand the credibility of VGI. Metadata is also an issue with [PERSON] [27] suggesting that the \"complete disregard for documentation of data resources\" has made it almost impossible for one to perform a fitness for use or fitness for purpose evaluation on available data resources. Without some quantitative measures of accessing the quality of the OSM data the GIS community has been slow to consider OSM as a serious source of data [18]. Imports of government or National Mapping Agency (NMA) data into OSM, as mentioned in Section 1 is the exception rather than the rule [28].