## 2 Literature Overview
The \"contributors are spontaneous and the density of data is unpredictable\" and consequently the spatial distribution of the data itself will continue to be uneven and inconsistent. [PERSON] and [PERSON] [29] remark that for VGI in general the \"professional and scientific gate-keeping that usually filters and reviews digital information may not be present (in sufficient forms or structures)\" and subsequently can lead to information which is prone to being \"poorly organized, out-of-date, incomplete, or inaccurate\". [PERSON] and [PERSON] [30] calls OSM \"spatially-rich and semantically-poor\". [PERSON] and [PERSON] [31] suggest that the quality of VGI is enhanced if proper metadata is created and maintained which details: types of changes and edits, methods of survey and collection, and finally a fitness for purpose statement. The recent study by [PERSON] and [PERSON] [16] of OSM and TeleAtlas for Germany shows that \"while professional data is not without its faults the coverage of OSM in rural areas is too small to be seriously considered a sophisticated alternative for _any_ applications\". However the study does conclude that for larger cities (Berlin, Frankfurt, Munich) the data diversity is so rich that \"OSM is replacing proprietary data for many projects\". Heterogeneity of the spatial data coverage in OSM is a real barrier. [PERSON] _et al._[32] show that the difference between the OSM street network for car navigation in Germany and a comparable proprietary dataset was only \(9\%\) in June 2011. In this study we analyse \"heavily edited\" objects in OpenStreetMap. We are unaware of any similar example in other sources of crowdsourced spatial data or VGI. In the next section of this literature review we make connections to research work carried out in Wikipedia. Similar to OSM it is possible to extract the entire history of edits to articles in Wikipedia. A growing body of literature is available on this topic. The crowdsourced collection and collaborative editing of spatial data in OSM is unique and is certainly non-traditional for geographical data. The literature available dealing with these topics in relation to OSM is still rather limited. There is a very substantial collection of literature on Wikipedia where the equivalent to the OSM collaboratively edited object is the _article_[33]. We feel that it is useful to briefly introduce some key outcomes from research studies of the collaborative editing nature of Wikipedia. Heavily edited articles in Wikipedia are usually those that gain the status of \"featured article\". Featured articles are recognized as articles of high quality, with a long history of collaborative editing, and have become relatively stable (no major recent edits) [34]. In [PERSON] _et al._[35] the authors introduce a measure of article quality for featured articles based on the succeeding edits by other users. Subsequent edits (deletions) and roll-backs to earlier versions are considered as disapproval whereas maintaining the edits of previous editors is deemed as a sign of approval. [PERSON] _et al._[33] analyzed the history of edits of Wikipedia and identified a number of specific users, most notably _Substantive_ editors. Substantive editors contributed, at minimum, between \(30\) and \(80\) percent of all content edits to pages. Overall research appears to indicate that there does not appear to be a \"standard contributor\" to Wikipedia or standard pattern of contribution. [PERSON] and [PERSON] [36] conclude that frequent Wikipedia users (like _Substantive_ users by [PERSON] _et al._[33]'s definition) may contribute knowledge by making minor changes to Wikipedia entries. Conversely, some users who contribute infrequently may provide extremely rich content. [PERSON] [37] reports in a survey of Wikipedia contributors that many contributors are worried about how \"individual agendas could shape editing behaviors\" particularly those edits from very frequent contributors.