This topic defines the core terms used in Raster SQL.
| Term | Description |
|---|---|
| raster object | A raster object (also called a raster) divides space into a regular grid of cells. Each cell holds an attribute value representing a real-world entity. Common examples include satellite images, digital elevation models (DEMs), and photographs. |
| cell / pixel | The smallest unit of a raster object — a single grid square, also called a pixel. Each cell supports the following data types: Byte, Short, Int, and Double. |
| band | A single matrix of cell values within a raster object. A raster can have multiple bands. |
| chunk | A subdivision of a raster object used for storage and processing. Chunk size is configurable — for example, 256 × 256 × 3. |
| pyramid | A series of downsampled versions of a source raster object, used to improve display and query performance. Pyramids allow the system to retrieve only the resolution needed for the current view: a low-resolution layer renders the full dataset quickly, and finer layers load as you zoom in. Each consecutive layer is downsampled at a 2:1 scale. Layer 0 stores the original full-resolution data. |
| pyramid level | A single layer in a raster pyramid, representing the data at a specific downsampled resolution. |
| mosaic | The operation that merges multiple raster objects into an existing raster dataset. |
| interleaving | The method used to organize pixel values from multiple bands in storage. Three methods are supported: band sequential (BSQ) stores all values for one band before the next; band interleaved by pixel (BIP) stores all band values for one pixel before the next; band interleaved by line (BIL) stores all band values for one row before the next. The choice affects read performance depending on whether access patterns are band-oriented or pixel-oriented. |
| world space | The geographic coordinate space of a raster object. |
| raster space | The pixel coordinate space of a raster object, with the upper-left corner as the origin. Use raster space when referencing pixel positions directly rather than geographic locations. |
| metadata | Descriptive attributes of a raster object, including its spatial range, projection type, and pixel type. Remote sensing platform metadata is not included. |