Several cartographic conventions can help readers make sense of a map. Not following these conventions can make your map difficult to interpret.

What readers expect in a map

Readers expect that a map will:

  • be drawn in 2 dimensions as seen from above, or on a globe
  • be oriented so that north is at the top, with a compass symbol
  • include a scale as either a bar with labelled divisions or a ratio (e.g. 1:25,000)
  • include a legend to colours and symbols
  • use universal colours (e.g. blue water, brown land, green vegetation, white ice)
  • include a coordinate system such as a number and letter grid (e.g. a street map), or lines of latitude (east–west parallels) and longitude (north–south meridians)
  • include a declaration of the projection type or method, where relevant (e.g. equidistant, equal area, conformal)
  • include alternative text for accessibility, if published online
  • provide other necessary information that is critical to understanding the map.

Primary map elements

Title

The following principles are recommended:

  • Number maps consecutively within the document (e.g. Figure 1, Figure 2, Figure 3), or by section or chapter (e.g. Figure 2.1, Figure 2.2, Figure 4.1, Figure B5). Numbering by section is useful because changes in one section will not affect numbering in another section. This is especially important in long documents or those that have many figures. Alternatively, maps could be numbered Map 1, Map 2, and so on, if there is a requirement to separate maps from figures within the publication.
  • Place the title as its own paragraph below the map, not within the map. This convention should also be used for web-based publications. However, placing the title just above the legend may be more suitable for some types of page layout designs. A subtitle may be useful to provide additional information, such as a location or key finding.
  • Avoid obvious titles such as Map showing x and any jargon that will confuse the reader.
  • Use a title that describes the map content, including the date of the map, if appropriate:
Figure 3     Salvinia (Salvinia molesta) weed spread and management actions, 2011
  • Use minimal capitalisation for the title (only capitalise the first letter of the first word of the title and proper nouns).
  • Use minimal punctuation to keep titles clean and uncluttered: follow figure numbers with a tab, not a colon, and do not place a full stop at the end. Using a tab also helps align the titles properly in an automatically generated contents list of figures.
  • Spell out abbreviations in full in the title, wherever possible. Put any necessary detail in explanatory notes. The title should not cover more than 2 lines (preferably 1 line).
  • For a series of maps, give the same information in the same order in the title.

Legend

A legend explains all symbols and colours used on the map. Complex or detailed legends may require grouping of categories or shape types. A legend title such as key or legend is not required. Outlines (boxes) around the legend can make a map look cluttered and are not usually necessary. Legend labels should use minimal capitalisation, and standard editing and numerical conventions (see Style and editing).

Scale

Most maps should include a scale bar. This is conventionally placed within the map area itself, most often at the bottom, although it could also be placed near the legend if there is no space at the bottom.

The scale bar should be roughly one-fifth of the width of the map and indicate distance intervals in whole numbers that are meaningful for the purpose of the map, starting at 0 at the left end of the bar (e.g. 0, 25, 50, 75, 100 km). The scale bar is occasionally accompanied by the statement of scale, such as 1:100,000. However, the written statement of scale will not be correct if the map is enlarged or reduced, and should be removed before publication. The scale bar is not affected by enlargement or reduction of the map.

Geoprofessionals use the following terms to define map scales:

  • small scale – 1:250,000 and smaller
  • medium scale – 1:50,000 to 1:250,000
  • large scale – 1:50,000 and larger.

These classifications vary slightly in absolute terms (Peterson 2015) and are often used in a relative sense. An easy way to remember the classification is that large-scale maps show small areas such as a town, and small-scale maps show large areas such as continents.

Other map elements

North arrow

The north arrow was once a primary element for orientation of a map to the reader. However, contemporary convention dictates that the top of the map is north, so the arrow is no longer needed. A north arrow does need to be included when a map is not aligned with north at the top, or additional information about direction is required, such as magnetic north.

Production information

Production information can include:

  • author
  • date of publication
  • publisher
  • limitations of what is shown on the map
  • citations
  • projection
  • disclaimers
  • logos
  • copyright.

Some of this information may need to be removed from the map when it is produced within a report or publication. In such cases, the production information may be transferred to credits or acknowledgments within the publication itself.

Inset maps

Inset maps are small, additional maps, which may require their own scale bar. They have 2 main functions:

  • to zoom out of the primary map to show location (locational diagram)
  • to zoom in on an area of the primary map to show more detail (enlargement).

The features, styles and orientation for the inset map should be the same as for the primary map. For zoom-in inset maps, it is important to indicate the position of the inset map in relation to the primary map using a box or shading. Leader lines coming from the box on the primary map can be used to connect with the box of the inset map.