## 2 Materials and Methods
### Requirements for the Earth-System Spatial Grid
#### 2.1.2 Principles and Requirements for the Earth-System Spatial Grid
Multi-Scale Dynamic Adaptability Criterion Earth-system phenomena exhibit multi-scale spatiotemporal characteristics, from long-term climate cycles (e.g., glacial-interglacial shifts) to short-term meteorological events (e.g., thunderstorms), and from continental drift to localized seismic activity. This criterion demands grids that capture macro-scale trends (e.g., ocean circulation, ecosystem patterns) and micro-scale details (e.g., urban heat islands, soil erosion). Building on [PERSON]'s \"Hierarchy\" and \"Scalability\" principles, this criterion emphasizes real-time or near-real-time tracking of dynamic changes. For instance, in wildfire monitoring, low-resolution grids rapidly identify fire-prone areas, while dynamic refinement to high-resolution grids tracks fire spread and ecological impacts, enhancing disaster response. ESSG must support asynchronous multi-resolution grids--infinitely subdivisible and adaptable across dimensions--to address diverse application needs. Global Seamless Partitioning Criterion  
Earth's volumetric space spans from its core to outer space. This criterion requires grids to fully and seamlessly cover this domain, accounting for Earth's non-spherical geometry, surface topography (mountains, oceans, canyons), and heterogeneous layer thicknesses. Grids must naturally transition between terrestrial, marine, and atmospheric regions, including extreme terrains like ocean trenches and mid-ocean ridges. Extending [PERSON]'s \"Global Coverage\" to 3D, this principle ensures comprehensive data foundations for multi-layer research. Encoding Uniqueness and Efficiency Criterion  
The uniqueness and high efficiency of coding require each grid unit to have a unique coding and support efficient coding and decoding operations. The spatial data of the Earth system are massive and complex, and the traditional latitude and longitude coding method is inefficient at high resolution. The criterion of coding uniqueness and high efficiency requires the grid system to adopt a compact and unique coding scheme, to ensure that each grid unit has a unique logo on a global scale, and to support efficient coding, decoding, and spatial indexing operations. This high efficiency can not only improve the efficiency of data storage and retrieval, but also support the real-time processing and analysis of large-scale spatial data, providing more efficient computing support for multi-layer research. Data Fusion and Multi-Source Compatibility Criterion  
ESSG must integrate multi-source data (remote sensing, ground observations, simulations) with varying formats, resolutions, and semantics. A unified fusion framework ensures seamless interoperability, improving data utilization efficiency and enabling cross-layer analysis. The Earth-system space grid represents a new development direction for geographical space grids, evolving from planar grids to three-dimensional grids, and from spherical grids to spherical body grids, and extending to the Earth's layered space. Looking back on the construction concepts of spherical grids and spherical-body grids, spherical space grids abstract the Earth's space into a spherical space, which is suitable for expressing various spatial objects on the Earth's surface. However, it is difficult to scientifically and rigorously describe the three-dimensional objects within the Earth's space. On the other hand, spherical-body space grids abstract the Earth's space into a spherical body space. In essence, they regard the Earth's space as a sphere with a uniform interior. Although there is also a radial hierarchical structure, this hierarchical structure cannot be adjusted as needed. It can only approach the given layer plane as closely as possible through radial subdivision, and it does not fully reflect the characteristics of the layered structure. Therefore, simply abstracting the Earth's layered space into a spherical body is insufficient for constructing a layered space grid.