What is and What is not the Digital Earth
The article addresses to a fundamental issue facing the concept of the Digital Earth in 2020 – what is the definition of the Digital Earth? 22 years after the announcement of the concept and 15 years after its first mass and successful implementation in the service Google Earth in 2005 this question remains unanswered. In the article the current status of the development of the Digital Earth concept by 2020 is considered, a methodology for the definition of the Digital Earth, based on the classification of the diversity of existing geospatial approaches and the identification of key factors that provide its unique functionality, is proposed and discussed. Distinction between the Digital Earth and others geospatial approaches is provided. The intrinsic connection of definition and classifications is grounded, the new definition of the Digital Earth and complimentary classification of geospatial methods are offered. Semiotics aspects of the Digital Earth are discussed briefly. The question of the eligibility of technologies and systems to the Digital Earth is considered. The perspective issues of further development of the Digital Earth are considered.