Why raster data?
• Rasters can represent
better than vectors, e.g.:
• Gradients in vegetation
Can you name a few more?
• Discrete rasters: integer values representing classes
• E.g. Land-use map, soil map
• Continuous rasters: real values representing features
without sharp borders
• E.g. DEM, temperature map, soil moisture map, runoff map
• Boolean rasters: 1 or 0, representing true or false
Single band rasters
Monochromatic image Gray scale image Color image
Consist of several single band rasters.
Each band relates to a range
in the electromagnetic
spectrum collected by a sensor.
Bands are commonly displayed as red
green and blue composits (RGB).
Continuous raster data - examples
• Remote sensing data
• Digital Elevation Models
• Interpolated point data
Vector versus Raster
• Raster data is computationally less expensive to render than vector graphics
• Transparency and aliasing problems when overlaying raster data
• Vector data allows for visually smooth and easy implementation of overlay operations
• Vector data can be easier to register, scale, and re-project
• Vector data is more compatible with relational database environments, where they can
be part of a relational table as a normal column and processed using a multitude of
• Vector file sizes are usually smaller than raster data, which can be tens, hundreds or
more times larger than vector data
• Vector data is simpler to update and maintain, whereas a raster image will have to be
• Vector data allows much more analysis capability, especially for "networks" such as
roads, power, rail, telecommunications, etc.