A Survey of Digital Earth

• We provide definitions of Digital Earths and discrete global grid systems.
• We discuss different data sets that are represented on Digital Earths, the methods of their acquisition, and the techniques for rendering and processing them.
• We discuss each component of discrete global grid system such as refinement, indexing, and projection.
• We provide some state of the art techniques to provide a discrete global grid system.
• Finally, we study applications of Digital Earths in different areas such as environmental monitoring and education.

The creation of a digital representation of the Earth and its associated data is a complex and difficult task. The incredible size of geospatial data and differences between data sets pose challenges related to big data, data creation, and data integration. Advances in globe representation and visualization have made use of Discrete Global Grid Systems (DGGSs) that discretize the globe into a set of cells to which data are assigned. DGGSs are well studied and important in the GIS, OGC, and Digital Earth communities but have not been well-introduced to the computer graphics community. In this paper, we provide an overview of DGGSs and their use in digitally representing the Earth, describe several current Digital Earth systems and their methods of Earth representation, and list a number of applications of Digital Earths with related works. Moreover, we discuss the key research areas and related papers from computer graphics that are useful for a Digital Earth system, such as advanced techniques for geospatial data creation and representation.

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