Quick Insight
Raster data represents geographic information as a grid of equally sized cells, or pixels. Each cell contains a value that describes something about the area it covers, such as elevation, temperature, rainfall, land cover, or the colors in a satellite image.
Raster data is especially useful for information that changes across an area rather than following precise boundaries. For example, elevation can vary from one part of a landscape to another, and raster cells can record those changes across the entire area.
Why Raster Data Matters
- It is well suited to continuous information such as elevation, temperature, rainfall, and air quality, where values can vary across an area.
- It is widely used for analyzing satellite and aerial imagery, including measuring vegetation and changes in land cover.
- It supports terrain and flood analysis by allowing analysts to model elevation and identify areas that meet certain elevation or risk thresholds.
- Its level of detail depends on resolution. Larger cells provide less detail, while smaller cells capture finer geographic variation and generally require more storage.
Types of Raster Data
- Continuous raster data: Values can vary gradually across the grid, such as elevation, temperature, or rainfall.
- Discrete raster data: Each cell represents a distinct category, such as forest, water, urban area, or agricultural land.
Frequently Asked Questions
1. What's the difference between raster and vector data?
Raster data represents geographic information as a grid of cells, making it useful for surfaces and imagery. Vector data represents features using points, lines, and polygons, making it useful for defined features such as buildings, roads, and property boundaries.
2. What's an example of raster data?
Satellite imagery, digital elevation models, temperature maps, and rainfall datasets are common examples of raster data. Each cell in the grid stores information associated with a specific geographic area.
3. What does "resolution" mean in raster data?
Resolution refers to the size of each raster cell on the ground. Higher-resolution raster data uses smaller cells and can show more detail, while lower-resolution data uses larger cells and provides less detail.
4. What file formats are used for raster data?
Common raster formats include GeoTIFF, NetCDF, and cloud-optimized GeoTIFF (COG). Image formats such as PNG and JPEG may also be used for map tiles and visual imagery, although they do not necessarily contain the geographic information stored in a GIS raster dataset.
5. Is a raster the same thing as a raster tile?
No. A raster is the underlying grid of geographic data. A raster tile is a smaller portion of a raster dataset, typically created so large datasets can be loaded and displayed more efficiently on digital maps.
