This topic defines the core terms used in Raster SQL. Raster data represents continuous spatial phenomena — such as elevation, temperature, and land cover — as a grid of cells. Understanding how these terms relate to each other helps you write correct queries and interpret results.
The terms are grouped by function:
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Data structure — how a raster object is organized internally
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Coordinate systems — how pixels map to geographic locations
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Storage and performance — how data is physically arranged and optimized
Data structure
| Term | Description |
|---|---|
| raster object | A regular grid that represents a geographic space. Each cell holds an attribute value that models a real-world entity. Common raster objects include satellite images, digital elevation models (DEMs), and a picture. |
| cell/pixel | A single element in the raster grid, also called a pixel. Supported data types include byte, short, integer, and double. |
| band | A single matrix of cell values that measures one characteristic of a raster object. A raster object can have one or more bands. |
| mosaic | An operation that merges one or more raster objects into an existing raster dataset. |
Coordinate systems
| Term | Description |
|---|---|
| raster space | The pixel coordinate system of a raster object. The top-left corner of the raster object is used as the starting point. |
| world space | The geographic coordinate system of a raster object. |
| metadata | Descriptive information attached to a raster object, including its spatial extent, projection type, and pixel type. Metadata from the remote sensing platform is not included. |
Storage and performance
| Term | Description |
|---|---|
| chunk | A rectangular tile that subdivides a raster object for storage and retrieval. Chunk size is configurable — for example, 256 × 256 × 3. |
| pyramid | A set of progressively lower-resolution copies of a raster object. A pyramid can contain one or more downsampled layers. Consecutive pyramid layers are downsampled at a 2:1 scale. Layer 0 stores the raw data. |
| pyramid level | A single layer within a pyramid. |
| interleaving | The physical arrangement of pixel values across bands in storage. The interleaving types include band sequential (BSQ), band interleaved by pixel (BIP), and band interleaved by line (BIL). |