Overlay Analysis is to extract the new Spatial Geometry Info required by the user through the processing or analysis of Spatial Data. For example, if we need to know the soil distribution in a certain administrative region, we can carry out Overlay Analysis according to the two Datasets of Land Use Map and Administrative Region Planning Map of the whole country to get the results we need. At the same time, various Attributes of data can be processed through Overlay Analysis.
Overlay Analysis is widely used in resource management, urban construction evaluation, land management, agriculture, forestry and animal husbandry, statistics and other fields.
Space Overlay Analysis involves the operations of logical intersection, logical union, logical difference and exclusive or. For the convenience of discussion, Euclidean space layers A, B and C are defined as binary images here. The following table introduces the properties and laws of layer Boolean logic operations.
| Logic operation | Definition | Nature | Explain |
| Include | If X X ∈ A, X X ∈ B, then A is called a subimage of B or B contains A, denoted by A AB. | (1) A⊆A (2) A⊆B，B⊆C ⇒ A⊆C (3) A⊆B，B⊆A ⇒ A=B |
If A AB, A AB, call A proper subimage A AB of B. We use Ω to denote an image and φ to denote the empty image. |
| Hand in | The intersection of A and B is defined as A ∩ B = { X | X X ∈ A and X X ∈ B } | (1) A∩A = A (2) A∩φ = φ (3) (A∩B)∩C = A∩(B∩C) |
A is said to be disjoint from B if a ∩ B = φ. |
| And/or | The union of A and B (also called or) is defined as A AB = { X | X X ∈ A or X X ∈ B } | (1) A∪A = A (2) A∪φ = A (3) (A∪B)∪C = A∪(B∪C) |
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| Poor | The difference between A and B is defined as A-B = { X | X X ∈ A, and xB } | (1)A-φ = A (2) A-A = φ (3) (A-B)-C = A-(B∪C) |
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| Xor | The Xor of A and B is defined as: A AB = { X | X X ∈ A or X X ∈ B, and X A ∩ B } |
The following figure shows the Boolean logic operations of inclusion, intersection, union, difference and exclusive or.
Instructions for use
A Region Dataset participating in Overlay Analysis cannot have overlapping face objects. The Dataset with overlapping face objects is illegal, and the system cannot guarantee the correctness of the overlay result. It is recommended to perform Topology Check before Overlay Analysis.
The face overlap is shown in the following diagram:
Precautions
- In the two Datasets for Overlay Analysis, the type of Dataset for Overlay Analysis can be point, line, surface, etc., which is called Input Data: set (called the first Dataset in SuperMap GIS); The other Dataset is the Region Dataset, called the Overlay Dataset (called the second Dataset in SuperMap GIS).
- It should be noted that the Region Dataset or the recordset itself should avoid including overlapping regions, otherwise the Overlay Analysis Result may be erroneous.
- The data for Overlay Analysis must be the same georeferenced data, including Input Data: and Result Data.
- When the data volume of Overlay Analysis is large, Result DatasetCreate Spatial Index is required to improve the Display Speed of the data.
Related topics
Overlay Analysis Operator Introduction