Introduction to Geographic Information Systems

What is GIS?

• GIS is a computerized system designed for the storage, retrieval, and analysis of geographically referenced data.
• It uses advanced analytical tools to explore spatial relationships, patterns, and processes at a scientific level.
• These processes can be cultural, biological, demographic, economic, geographic, and physical phenomena.

Components of GIS

• GIS includes a geographic component that relates to location.
  • The majority of the data collected is associated with some location in space.
• It also includes an information component that is the data attached to a location.
  • Tables, attributes, or characteristics can be used to symbolize and provide insight into a given location.
• GIS also relies on systems, where many components work together to achieve a common goal.
  • This requires hardware, networks, software, data, operational procedures, and people.

Principle Components of GIS

• Software
• Data
• Methods
• People
• Hardware

Geographical Features and Databases

• GIS stores information about the world as a collection of thematic layers.
• Layers are linked together by geography using overlay analysis.

Basic Capabilities of GIS

• Data is spatially referenced using map projections and coordinate systems
• Spatial data layers can be overlaid, manipulated, and combined to form composite layers.
• Spatial features are linked to tabular data via a relational database

Spatial Data Model Types

• Data objects form a spatial database with relationships.
• There are three fundamental means for organizing spatial data: vector data, raster data, and tabular/attribute table data.

Vector Data

• Vector data represents features as points, lines, polygons, and TINs with (X, Y) coordinated and associated attributes.
• Points are stored by their (X, Y) location and table attributes
• Lines are stored by the sequence of first and last points, as well as the associated table attribute.
• Polygons consist of one or more lines that enclose an area and have 2D properties with area and perimeter
  • Polygons represents cities, geological formations, dikes, lakes, rivers, etc
• TINs (Triangular Irregular Network) is a vector approach to handling a digital elevation model in 3D Models.
  • TINs interpolate surfaces using multiple triangles
  • TINs interpolate surfaces by selecting representative data points connecting to continuous and connected triangles.
  • Data points consist of X, Y, and Z values, with the final result providing a TIN surface.

Raster Data

• Raster Data displays information that is continuous across an area and cannot easily be divided into vector features.
• It represents the world as a surface divided into a regular grid of cells.

GIS Applications

• GIS can be used in banking, financial services, facilities management, insurance, media, press, real estate, and retail.
• Other uses include: defense, intelligence, health and human services, mapping, charting, public safety, and transportation.