In the vector (or topological) data structure information is stored as points, lines and polygons. A polygon is an area bounded by a closed loop of straight line segments (Aranoff, 1989).

This sort of representation is similar to how objects would be shown on a map. The position of each object is defined by its placement in a map space that is organised by a coordinate reference system.

• It is a much more complex data structure than the simpler raster model
  
  
• Overlay operations are more difficult
  
  
• The representation of high spatial variability is inefficient
  
  
• It is computationally more intensive to perform tasks using a vector structure than using a raster model
  
  
• Vector structures cannot effectively manipulate and enhance digital images