## 2 Volunteered Geographic Information  
The term volunteered geographic information (VGI), coined by [PERSON] [1] in 2007, describes the process of collecting spatial data by individuals, most times on a voluntary basis. In most cases, the contributed VGI is collected in a database or file system structure and sometimes freely available to other interested Internet users. To be able to contribute to one of the VGI platforms, the information has to match a geographic position. This can either be achieved by tracing it from georeferenced aerial imagery or by actively collecting GPS tracks with a designated device. Furthermore, a broadband Internet connection and additional hardware in the form of a smartphone or personal computer are needed. Although these prerequisites seem to be trivial in most modern societies, we will discuss at a later point that they tend to explain certain patterns in the global distribution of VGI projects.  
The steep increases in VGI contributions lead to a number of diverse platforms and projects utilizing the data and technologies in spatial decision making, participatory planning and citizen science [24]. VGI data also experienced more attention, due to its successful implementation for humanitarian or crisis mapping purposes [4]. In this context, the Humanitarian OpenStreetMap Team (HOT) [25] obtained an important role. Since 2009, it has coordinated the creation, production and distribution of free mapping resources to support humanitarian relief efforts in many places around the world. Ushahidi [26], a different platform that collects humanitarian crisis information, was initially developed to map reports of violence in Kenya in 2008 and has evolved into a valuable tool during a number of projects in recent years. The potential of VGI has also been proven for urban management purposes [27], flood damage estimation [28], wild fire evacuation [29] or other important cases of risk, crisis and natural disaster management [30; 31; 32] or responses [33; 34; 35].  
The reason why VGI is implemented in many of these scenarios is its open approach to data collection. VGI is sometimes the cheapest and oftentimes the only source of geo-information, particularly in areas where access to geographic information is considered an issue of national security [1]. The aforementioned Internet connection, essential for data contributions to VGI platforms, can be a serious caveat in developing countries, which, in combination with language issues based on the fact that many VGI services only support the Roman alphabet in the English language and large analphabetic population rates, can hinder the contributions to a VGI project in these areas [1]. However, despite these facts, the OSM project has developed into one of the largest and well-known VGI projects of the past seven years. Many different OSM-based maps have been created in recent years, tailored to different purposes, such as skiing, hiking or public transportation, by rendering the collected information in a particular way. More advanced projects, such as OpenRouteService [36; 37] or OSRM [38], have shown that collaboratively collected geo-information by volunteers can be a reliable data source for car, bicycle, pedestrian and possibly wheelchair or haptic-feedback routing or navigation applications. Based on the increasing success of the OSM project, several other companies implemented the idea of collaboratively collected or corrected geographic information for their own business solutions or data sources.