How does GIS store and analyze geographic information?

A GIS (Geographic Information System) functions as a computer system designed to store, retrieve, and analyze spatial data by building upon traditional cartography.

Data Storage

GIS stores geographic information as a collection of thematic maps, often referred to as layers or themes. These are managed using two primary computer graphic formats:

• Vector-based: Represents point entities as coordinate pairs, lines as sequences of points, and areas as polygons. Descriptions are stored in tabular data linked to these graphic objects.
• Raster-based: Represents space as a grid of uniform cells. Surfaces are stored as a matrix of values, such as elevation in a digital elevation model (DEM).

Analysis

GIS analyzes information by manipulating data within individual layers or by overlaying multiple thematic maps to compare specific geographic features. Operators use computer algorithms to perform complex tasks, including:

• Finding optimal routes and service areas.
• Creating viewsheds (line-of-sight maps).
• Performing statistical manipulations.
• Developing sophisticated models to simulate flows, such as traffic or water movement, through a process known as cartographic modeling.1