When producing a data visualisation (map), you need to think of the following topics.

  1. Defining the context
  2. Symbolising the data
  3. Layout

Although there is some chronological order in these topics, some cyclic iteration is often involved before a usable visualisation emerges.

Defining the context

This step is all about understanding your target audience, goals, media choice, and available resources. You should always make sure that you, at least in your own mind, are clear on the context you are working in before attempting to produce a data visualisation. You can learn more about this stage in the post “An overview of the design process behind a visual narrative“‘

Symbolising the data

The process of symbolising data can be described as creating a set of rules that define which symbology to apply to the geospatial data’s geometric information. These rules are typically based on the attribute values. The symbology consists of symbols for points, line symbology for lines and border and fill symbology for areas. All these symbologies can be layered on top of each other to create quite complex symbology. Exactly how you generate these symbolisation rules varies from software to software so see the software specific branches under the post “Symbolising geospatial data”. It can be, however, be helpful to think of the following three situations where different symbolisation principles apply:

  • Symbolising all entities in the same manner
    Typically used in the geospatial data contains a single entity type, i.e. forest, lakes, or a given type of protection zone.

    Contries with more train accidents in 2007 than in 2006
  • Symbolising the entities base on a nominal (categorical) attribute
    Typically used if the entities types have no rank relation, i.e. countries, municipalities or different types of amenities (schools, churches, supermarkets)
  • Symbolising the entities based on a numerical (interval or ratio) attribute
    Typically used when symbolising based on a statistical attribute such as income, life span or the number of rail accidents per country.

Layout

Most people read maps like text from top left to bottom right.  Therefore place what you want the reader to see first in the top right corner. This is typically a descriptive title. The for is typical “topic” in “area,” i.e. Rail Accidents in Europe. Do not write Map of Rail Accidents in Europe. Most readers can see it is a map, and you don’t need to explain it. Less essential things are placed in the top right or bottom right (out of the line from top left to bottom right). The important stuff should occupy the majority of the space and be located somewhere around 5% over the middle. The task of creating a good layout is relatively complex, so please read on in the post “Map layout”

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