From Discrete Global Grid Systems to Earth System Spatial Grid: A Review of 3D Extension, Encoding, and Applications

As Earth system science moves toward global-domain and multi-sphere coupling, traditional two-dimensional spatial information frameworks can no longer fully meet the integrated spatial computing demands of deep space, deep Earth, and deep ocean applications. Building on research in Discrete Global Grid Systems (DGGS), this paper provides a comprehensive review of Earth System Spatial Grid (ESSG) for three-dimensional Earth system modeling. It focuses on three major categories, namely shell-based, volumetric, and unstructured approaches, and examines their geometric construction, radial extension, and encoding mechanisms. The paper further summarizes representative applications of ESSG in geophysics, space sciences, digital twins, and spatial intelligence, and discusses future challenges including ellipsoid adaptation, international standardization, cloud-native computing, and four-dimensional spatiotemporal extension.