A valley at dusk seen from above, overlaid with glowing contour lines, point markers, roads and parcel outlines

Geographic Information Systems (GIS)

Geographic Information Systems

How points, lines and polygons become a living model of the world.

What is GIS

GIS links “where” with “what”.

A Geographic Information System is a framework for capturing, storing, managing, analysing and visualising data tied to locations on Earth.

It links where (coordinates) with what (attributes), so patterns, relationships and change can be seen and measured.

3Vector primitives
2Data models: vector, raster
4Dimensions of geometry, 0D to 3D

From Point to Volume

Every map is built from points, lines and polygons.

Each primitive adds one dimension to the last.

From Point to VolumeA 12-second loop: 0D → 1D → 2D → 3D
  1. Point0D · (x, y)
  2. Line1D · ordered vertices
  3. Polygon2D · closed ring with area
  4. Volume3D · polygon + height (z)

Point · 0D

A single coordinate pair.

  • Wells, trees, sensors, addresses

Line · 1D

An ordered sequence of points, with length.

  • Roads, rivers, pipelines

Polygon · 2D

A closed ring of lines enclosing an area.

  • Parcels, lakes, administrative boundaries

Volume · 3D

A polygon given height, or a surface given depth.

  • Buildings, terrain models, geological bodies

Two data models

Vector draws features; raster fills a grid.

Model What it stores Best for Formats
Vector Points, lines, polygons Discrete features Precise boundaries Shapefile, GeoJSON, GeoPackage
Raster Grid of cells A continuous grid; each cell holds a value Elevation, imagery, temperature GeoTIFF, COG

Overlay

Layers stack on one coordinate system, so they align exactly.

Raster terrain Roads · lines Parcels · polygons Points

GIS overlays thematic layers on a shared coordinate reference system (CRS), so every layer lines up with the others.

Common choices: WGS 84 · EPSG:4326 Web Mercator · EPSG:3857

Core operations

Capture, store, analyse, visualise.

01

Collect

Capture

GPS, survey, remote sensing and digitising.

02

Keep

Store

Spatial databases such as PostGIS.

03

Ask

Analyse

  • Buffer
  • Overlay
  • Network routing
  • Interpolation
  • Spatial statistics

04

Show

Visualise

2D maps, 3D scenes and dashboards.

Where GIS is used

Anywhere location shapes a decision.

Urban planning

Zoning, land use and growth scenarios.

Environment & climate

Habitats, emissions and change over time.

Transport & logistics

Routes, networks and fleet movement.

Agriculture

Field boundaries, soils and crop monitoring.

Disaster response

Hazard zones, damage and access routes.

Utilities & infrastructure

Pipes, cables and asset networks.

Open-source toolkit

A full GIS stack, free and open.

Desktop & database

  • QGIS Desktop
  • PostGIS Database

Data & services

  • GDAL/OGR Data conversion
  • GeoServer Web services

Web & open data

  • OpenLayers / Leaflet / CesiumJS Web maps & 3D globe
  • OpenStreetMap Open data