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A Map legend is a quick visual guide to understand the image of the map. As such it needs to explain the information being presented; the use of colour on the map, and any symbols or icons used.

In cartographic terms the Legend is used to describe the map (i.e. “Map Menu”) and as a summary of the colours and icons used (i.e. “symbology”).

Map Definition (Map menu)

A legend is used to quickly allow the user to identify visually they layers of information shown on the screen.

If the layers are communicating several types of information; they legend may group these together.

Note that not all map layers are required to be listed in the legend: Often background layers are omitted to allow the user to focus on the key information being displayed.

Other common Map menu items include:

  • Map Title: Describing the region or purpose of the Map

Colour and Icons Used (Symbology)

For Layers that produce complex symbology further detail to explain the symbols will be needed:

  • Continuous: When theming on a continuous value such as height often a smooth gradient of colour is used
  • Categorisation: When categorising information into groups the groups will need to be listed and provided a unique colour and appearance
  • Symbol Definition: When using distinct icons (or glyphs) to represent data points each shape will need to be listed along with a definition of what the symbol means. This can be relaxed when using a standard or well under known symbology set such as provided by MIL2525b or Emergency Response symbols for which the operator has been trainined.

Related reference

Legend View

Cartography - Legend (Wikipedia)

NATO Military Symbols For Land Based Systems

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