## 2 Volunteered Geographic Information: The OpenStreetMap Project
Additionally, the analysis revealed that the more volunteers contributed within an area, the more recent the objects were, i.e. providing a better temporal quality of OSM itself. Similar to all prior findings, an analysis for Ireland showed that the data completeness in OSM loosely correlates with the population density [14]. However, contradicting results to the pattern found in Europe could be determined for the US. In this particular case urban areas only showed similar data completeness between OSM and commercial providers in Florida, while rural areas were more complete in OSM [15]. This difference was primarily based on the TIGER/Line data import in OSM for the US and not due to active data contributions [15]. The heterogeneous pattern of the OSM project is not limited to data completeness and accuracy factors. The community and its active contributors show a similar distribution. At the beginning of 2012, about 75% of all members who made at least one change to the database were located in Europe, while the rest was distributed over the world [16]. Especially some countries with higher population values such as USA, China and India show relatively small OSM project communities. Although the project was initiated in the UK, the most active community of the project in recent years can be found in Germany [16]. The latest results showed that about 25% of all active OSM members are located in Germany. Thus, it is not surprising that the road network completeness shows good results, sometimes exceeding commercial providers for this particular area [17]. Solely attribute information such as road names, speed limits and turn restrictions are missing for parts of the German dataset [12, 17]. Aside from road network parameters, which are the main focus of most conducted analyses, a few other publications also confirm OSM data to be suitable for 3D city models in urban areas [18, 19]. In summary, almost all prior studies show that urban areas provide better data completeness in OSM than rural areas [20, 21], which is sometimes also referred to as \"urban bias in VGI\" [22]. However, each individual case study needs to be analyzed for its particular purpose [22, 23]. Chances are that: \"When one moves away from large urban centers the major issue for quality becomes one of coverage--in many rural areas there is little or no OSM coverage at all\" [24]. While most studies analyze the quantity and quality of the collaboratively collected information in OSM, others focus on the motivational factors of the volunteers that contribute to VGI projects [25, 26, 27]. Possible motivational factors might be the unique ethos, or that geospatial information should be freely available to everyone. For others, learning new technologies, self-expression, relaxation and recreation or just pure fun can play a major role [28]. Three independent surveys in 2009 [28], 2010 [29] and 2011 [30] gave more insight on demographic aspects of the OSM project. The majority of the contributors to the project, about 97%, were males. Two out of the three surveys [28, 30] showed that on average 65% of the respondents were between 20 and 40, and about 23% between 40 and 50 years old. Furthermore, about 56% had a high-school or higher education degree. About 50% of the respondents in one survey considered their current profession as computer science related [30] and another survey showed that about 50% had some sort of GIS background [28], highlighting that \"the OSM community does not constitute with GIS amateurs as is speculated in VGI\" [28]. Community-based projects, websites and portals such as OSM are oftentimes affected by so-called \"participation inequality\". A 90-9-1 rule can usually be applied to most of these projects [31]. This rule highlights that about 90% of the members of community-based projects are usually only consuming the collaboratively collected information, while 9% occasionally contributes to the project and only 1% demonstrate a very active pattern.