In GIS, there are 2 basic spatial data types representing the real world:

Raster and Vector

In this example, our landscape consists of

• rolling hills
• grassland
• lake
• rivers
• forest stands
• marsh

It can be represented as a series of raster layers and/or vector layers.

Raster Data

In the raster data model, land cover is represented as:

• single square cells

Each cell will have a value corresponding to its land cover type.

Raster data are good at:

• representing continuous data (e.g., slope, elevation, chemical concentrations)
• representing multiple feature types (e.g., points, lines, and polygons) as single feature types (cells)
• rapid computations ("map algebra") in which raster layers are treated as elements in mathematical expressions
• analysis of multi-layer or multivariate data (e.g., satellite image processing and analysis)
• hogging disk space

In the vector data model, features on the earth are represented as

• points
• lines / routes
• polygons / regions
• TINs (triangulated irregular networks)

Vector data are good at

• accurately representing true shape and size
• representing non-continuous data (e.g., rivers, political boundaries, road lines, mountain peaks)
• creating aesthetically pleasing maps
• conserving disk space

Different types of data are
stored in different
file formats.

images © ESRI

How are information about spatial features stored in a GIS?

back to Spatial Referencing on to Attribute Data