Category: Foundations
Raster
A raster is a grid of pixels where each pixel stores a value, commonly used for satellite imagery and elevation models.
Also known as: grid data, pixel grid
Expanded definition
A raster represents space as a regular grid. Each pixel stores one or more values, such as reflectance in a spectral band, temperature, elevation, or a classification label.
Satellite imagery is usually raster data. Multi-band imagery is often stored as separate raster layers or as a single file with multiple bands.
Rasters are well suited for continuous phenomena, but they require careful handling of projection, pixel size, resampling, and nodata values. Small preprocessing choices can change results in downstream analysis, especially along edges and in mixed pixels.
Related terms
Pixel
A pixel is the smallest unit in a raster; it represents the sensor’s measurement over a ground area.
Vector
Vector data represents geometry as points, lines, and polygons, typically used for boundaries, roads, and field parcels.
GeoTIFF
GeoTIFF is a raster image format that embeds georeferencing metadata so pixels map to real-world coordinates.
NoData
NoData is a special value that means a pixel has no valid measurement, for example due to clouds or missing coverage.