## 2 Materials and Methods
### Encoding of the Temporal and Spatial Grid of the Earth System's Layers
#### 2.3.2 Encoding Structure  
The layer-body encoding is composed of temporal encoding, layer-surface encoding, and layer-radius encoding. The encoding method of OHQS is still used for the layered spatial grid on the layer surface. First, according to the Earth's reference layer surface and the top layer surface of the near-Earth space, the Earth's spatial layers are divided into the initial layer body (spherical shell), and then the initial layer body is continuously subdivided from two dimensions: the layer surface and the layer radius. The subdivision identification of the layer body should reflect the subdivision levels on the layer radius and  
Figure 15: Schematic diagram of temporal subdivision.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Temporal Resolution** & **Start Encoding** & **End Encoding** \\ \hline
100 y & \(1\) & \(10\) \\
10\({}^{\circ}\) & \(11\) & \(110\) \\
1 y & \(111\) & \(1110\) \\
1 m & \(1111\) & \(13110\) \\
1 d &  
the layer surface, as well as the number of a certain subdivision unit on the layer surface and the layer-radius surface. Among them, the numbering of the subdivision levels starts from 0 and increases sequentially; the number of a certain subdivision unit (i.e., the radius element) on the layer radius is numbered according to its sequence number in the total number of subdivision units of the layer radius at the current subdivision level, and the numbering order increases sequentially from the inside to the outside; the number of a certain subdivision unit (i.e., the layer cell) on the layer surface is consistent with the OHQS grid encoding, which is divided into \((i,j,k)\) encoding.  
The basic unit of encoding is the encoding component. According to the identification method of the subdivision of the layer body, the encoding components of the layer body include the number of the subdivision level of the layer radius, the number of the subdivision level of the layer surface, the number of the layer-surface unit, and the number of the layer-radius unit, as shown in Table 4.  
The formal structure of the layer-body encoding (SolidCellCode) is as follows:  
[Layer-Surface Unit Code]-[Layer-Radius Unit Code]-[Temporal Code]  
DatumSphereTag is the identification of the reference layer body, and DatumSphereID is the number of the reference layer body.  
The encoding structure combines spatial and temporal components:  
Layer-Surface Encoding: Uses a hexagonal three-axis coordinate system \((i,j,k)\) based on OHQS, with binary mapping (e.g., \((100,010,001)\rightarrow\{4,2,1\}\)).  
Layer-Radius Encoding: Employs equidistant bisection (e.g., \(l\)-\(k\) format, where \(l\) is level, \(k\) is segment).  
Temporal Encoding: Hierarchically subdivides time (e.g., \(1\) year \(\rightarrow\)\(111\), \(1\) day \(\rightarrow\)\(13111\)).  
Here is a coding case. For a point at (lat: \(40^{\circ}\) N, lon: \(116^{\circ}\) E, alt: \(100\) km, time: \(2023\)-\(02\)\(06\)\(12\):\(00\):\(00\)):  
Map to ISEA4H surface cell (e.g., level 3, code 421).  
Radial segment (e.g., level 2, \(k=3\)\(\rightarrow\)\(2\)-\(3\)).  
Add temporal code (e.g., \(1\) h \(\rightarrow\)\(385111\)).  
Resulting code: [DatumSphereID]-421-2-3-385111.