Raster and vector: two ways to represent geography
Compare a grid of values with discrete geographic features and learn why neither model replaces the other.
Why this matters
Satellite imagery, temperature surfaces, roads, study sites, routes, and boundaries are all geographic data, but they are not naturally represented the same way.
Learn it
Raster divides space into cells or pixels and stores a value for each cell. Vector represents discrete features with geometry such as points, lines, and polygons plus attributes. A temperature surface may fit raster well; named sensors fit vector well. Either kind of data can later be tiled for delivery, so 'tile' is not a third data model.
Work through an example
A heat map can show temperature as a raster surface while individual weather stations appear as vector points on top. The two layers describe related information at different levels.
Raster → cells/pixels with values
Vector → features with geometry + attributesPractice
- 1Use the raster/vector exercise to compare the two representations.
- 2Name one real phenomenon that is naturally continuous and one that is naturally a set of discrete features.
- 3Explain what information would be lost if you forced each into the other model.
Try it
Raster and vector
Raster stores values in a grid of cells or pixels. Vector stores geometry such as points, lines, and polygons. Both can be tiled for delivery.
Raster is useful for imagery, elevation grids, temperature surfaces, and other continuous fields.
What to watch for
Do not call all map imagery 'raster data' without considering whether it is only a rendered picture of underlying vector data.
Where this takes you
Choosing the right model helps with storage, analysis, styling, transmission, and how people interact with the data.