Learning objectives

• List the main forms of GIS output
• Describe the basic elements of a map
• Outline how three-dimensional output is handled in GIS
• Describe the output media used by GIS
• explain why maps are important decision aids
• Explain what is meant by a Spatial Decision Support System
• Describe how the Internet has affected GIS
• Explain what VRGIS is

• Output: not the final goal of GIS but the starting point for informed decision-making or problem-solving
• Map: the most common form of output
• Understanding of basic principles of map design necessary for effective communication of information and ideas
• Understanding of the complexity of the map design process helps appreciate the power of maps as a visualisation tool

Examples of GIS output from the Happy Valley GIS

Map Design

• Map design is a visual plan to achieve a goal. A well-designed map is balanced, coherent, ordered, and interesting to look at, whereas a poorly designed map is confusing and disoriented. Map design is both an art and science.
• Cartographers usually study map design from the perspectives of layout and visual hierarchy.
• Layout deals with the arrangement and composition of various map elements on a map. Major concerns with layout are focus, order, and balance.
• Visual hierarchy is the process of developing a visual plan to introduce the 3-D effect or depth to maps.

The basic structure of the conterminous USA layout template in ArcMap.

A visual hierarchy example. The two black circles are on top (closest to the map reader), followed by the gray polygon and the grid.

The interposition effect in map design.

Contrast is missing in (a), whereas the line contrast makes the state outline look more important than the county boundaries in (b).

Map design elements

• Frame of reference
  • Need to fix map location in 'real-world' space
  • Grids & graticules
  • North arrow
  • Numeric / graphical scale
  • Inset map
• Projection used
  • Projection can affect basic measurement such as area and distance
• Features to be mapped

• Level of generalisation
  • May need to remove unnecessary features
  • May need to offset for clarity
• Annotation used
• Symbolism employed
  • Use of colour (Ski run example)
  • Use of shape
  • Shading and texture
• Legend

Map components

Example map

Cartographic symbolism

Choices in choropleth mapping

• Shading patterns and colour
  • Denser/darker = more of
• Relationships between attribute values
  • Nominal -> contrasting colours/patterns
  • Ordinal -> ramped colour
• Classification system
  • Don't overdo number of classes
  • Choose class intervals carefully
• Choice of spatial unit
  • May not have much choice with this

Results from the British 2010 General election mapped using choropleth mapping and area and gridded cartograms

Non-cartographic output

• Tables & charts containing spatial and non-spatial data
• Multimedia: photos, linked images (street view) sat images, video & sound
  • Geotagged audio example
  • Real-time movie example
• Can be dynamically linked to the map

Example of linked displays in GIS

Example of multimedia content in GIS displays

Layering a pollution surface (nitrogen dioxide, NOx) onto virtual London

Different renditions of virtual London

GIS and Spatial Decision Support

• DSS
  • Used to tackle ill-defined or semi-structured problems
  • Designed to be used by non-technical users
  • Make data and models available sometimes by database interface
  • Generate a series of alternatives
  • Flexible
  • Multiple pass approach

PPGIS integrated with a geo-referenced threaded discussion forum

Example of poor quality output.

• Spot the mistakes.