Geosensors are defined as "...any device receiving and measuring environmental stimuli that can be geographically referenced." Large scale networks of geosensors have been in place for many years, measuring Earth surface, hydrological and atmospheric phenomena. The advent of the Internet led to a large expansion of such networks, and efforts like Global Earth Observation System of Systems (GEOSS) Initiative aim to connect them. Volunteered Geographic Information (VGI) The term Volunteered Geographic Information was coined in 2007 by geographer Michael Goodchild, referring to the rapidly growing volume of social and scientific georeferenced user-generated content being made available on the Web by both expert and non-expert individuals and groups. This phenomenon is seen as an emerging Geoweb that provides Application Programming Interfaces (API's) to software developers and increasingly user-friendly web mapping software to both scientists and the public at large. International community The International Journal of Digital Earth is a peer-reviewed research journal, launched in 2008, concerned with the science and technology of Digital Earth and its applications in all major disciplines. The International Society for Digital Earth is a non-political, non-governmental and not-for-profit international organization, principally for promotion of academic exchange, science and technology innovation, education, and international collaboration. Several International Symposia on Digital Earth (ISDE) have been held. There have been seven ISDE symposia and three Digital Earth Summits. Proceedings for many of them are available. The 7th Symposium was held in Perth, Western Australia in 2011. The 4th Digital Earth Summit was held in Wellington, New Zealand in September, 2012. Digital Earth Reference Model (DERM) The term Digital Earth Reference Model (DERM) was coined by Tim Foresman in context with a vision for an all encompassing geospatial platform as an abstract for information flow in support of Al Gore's vision for a Digital Earth. The Digital Earth reference model seeks to facilitate and promote the use of georeferenced information from multiple sources over the Internet. A digital Earth reference model defines a fixed global reference frame for the Earth using four principles of a digital system, namely: Discrete partitioning using regular or irregular cell mesh, tiling or Grid; Data acquisition using signal processing theory (sampling and quantizing) for assigning binary values from continuous analog or other digital sources to the discrete cell partitions; An ordering or naming of cells that can provide both unique spatial indexing and geographic location address; A set of mathematical operations built on the indexing