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Data Analysis and Visualisation: Maps

Tips for Maps

Maps are used in a wide range of fields to display data with a geographic component. Population characteristics, land use, or geologic data could all be visualised on maps. Creating map visualisations requires that a few unique considerations be taken into account. 

Orientation
If possible, maps should be oriented with north pointing to the top of the visualisation. In some cases it may be necessary to create a map in a different orientation, for instance in order to fit a map on a page. In these cases it is essential to include an arrow indicating the direction of north on the map. It is good practice to include a north arrow on all maps, even those with north oriented to the top, as your viewers can then be certain of the map's orientation.

Ease of reuse
Future users of your map will potentially want to incorporate your data into their own maps. To make it easy for them to georeference and reuse your map, you should make sure that you include the map projection used (e.g. Mercator, Orthographic, Mollewide, etc.), as well as several latitude and longitude markers. Having only one latitude and longitude tie point is not enough to make your map reusable!

Scale
It's good practice to include a scale on all maps, although this may not be necessary for maps that are at a continent scale or larger, depending on the purpose of the map. Map scales can be written as ratios, e.g. 1:10,000 where 1 cm on the map would be 100 m, or as graphical scales. Using a graphical scale is recommended as it will remain accurate even if your map is resized, whereas a written scale will become completely meaningless and even misleading if someone reproduces your map at a different size to the original.

Legend
All maps must have legends; you need to give people the information necessary to interpret the visualisation! If your field has any symbols or patterns that are conventionally used to represent specific mapped features, then make sure to employ those conventions.

Map patterns and fills
Patterns and fills are commonly used to present regional data on maps. If possible, try to limit the number of different patterns used on a map, as they increase visual clutter. Numerous different patterns on a single map will compete for attention and decrease the readability of a map. Using different colours for different categories, or different shades of the same colour for different ranges of the data can help keep your map easy to interpret. However, be aware that using colour to convey data can make your map unusable for people with vision impairments such as colour blindness, and try to pick a colour palette that is colour blind accessible using tools such as ColorBrewer.