Spatial Information Technology
Raster and vector data
Choose a format for a task.
GIS stores spatial data in two ways.
Raster data: the area is divided into a grid of cells (pixels), and each cell holds a value. The resolution depends on the size of the cells: smaller cells, finer detail. Raster suits aerial photographs, satellite images, scanned maps, and cheap backdrops.
Vector data: features are stored as points, lines and polygons (areas), using their coordinates. Vector data can also store topology: how features connect and touch (which roads meet, which areas are neighbours). Vector suits precise work, keeps files small, and makes it easy to analyse individual features.
Comparing them:
| Raster | Vector | |
|---|---|---|
| Structure | simple grid | points, lines, polygons |
| Overlay | easy | more complex |
| File size | large | compact |
| Best for | images, continuous surfaces | networks, boundaries, precise features |
Grid for images, coordinates for precision.
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