1. What is Geographic Information System (GIS)

Geographic Information System (GIS) is a system designed to store, manage and analyse spatial data. GIS is usually used to model the real world of large geographical extent. It provides a common platform and file formats for professionals from different domains to share spatial data. The difference between a GIS software as compared to a Computer-Aided Design (CAD) software like Rhino3D or Revit are:

  • CAD is rooted in modelling, thus has the capability to model detailed 2D and 3D geometries. GIS is rooted in mapping, thus has the capability to perform and visualise analysis. These analyses are usually in only 2D.

  • GIS has limited drawing capability as compared to CAD.

  • GIS manages mainly 2D data and has limited 3D capabilities as compared to CAD.

  • CAD files are usually drawings or 3D models. GIS files are usually databases and separated into 3 main geometrical type: polygon, polyline and point.

  • GIS files contain more than geometrical information. Non-spatial information (e.g. building type, land use type etc.) are usually appended onto the geometry. These information are usually used to perform spatial analysis.

1.1. Data Types

There are two main types of data in GIS. There are vector and raster data.

  • vector data: usually documented in shape (.shp) and GeoJSON (.geojson) files. These images are usually cartographic maps.

  • raster data: usually documented in geotiff format. These data are usually satelite images.