7.2 The 8 golden rules

This part aims to introduce the best practices to integrate in the reflection and the graphic implementation of your map.

TABLE OF CONTENTS

• 1. Graphic Semiotics
• 2. Skinning
• 3. The message
• 4. The public
• 5. Simplicity
• 6. Readability
• 7. Visual harmony
• 8. Reproducibility

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1. Graphic Semiotics

Edited by Jacques Bertin in 1967, graphic semiology is the set of rules that govern the construction of a system of signs or language allowing the graphic translation of an information.

It is based on a set of visual variables that allow for the appropriate representation of a data item according to its type.

It allows the expression of relationships of difference, order, association or quantity between each element.

To use semiotics properly is to produce visually good maps to transcribe information (size of a population, types of missions…).

COUNTER-EXAMPLE

This map does not follow the semiological rules that call for grading the same color in order to visualize a rise in values.

Source: “Top Mapping Mistakes” O.Ildefonso (2021)

By choosing different colors for values that are linked to each other, our eye perceives a difference between the counties and not an order.

Moreover, our eye perceives better the dark colors, which we associate with important values, which is not the case here.

EXAMPLE

Source: “Top Mapping Mistakes” O.Ildefonso (2021)

For more on this topic, check out these helpful resources on standard cartographic practices

• Book:“How to Lie with Maps” (M.Monmonier)
• Book:“Ways of Representing the World” (D.Dorling & D. Fairbairn)
• Article:Which color scale to use when visualizing data (L.C. Muth)

2. Skinning

A map without a skin is not a finished map. Some elements are essential for it to be complete and understandable, omitting some of them can complicate the reading and understanding of the map:

• Title
• Legend
• Orientation
• Scale
• Sources

The details of these elements are given in part 1 of the good mapping practices.

COUNTER-EXAMPLE

This map has no layout elements.

While one can understand and interpret the symbols in each administrative entity, one cannot locate the map, be sure what they indicate, etc. Therefore, this map is difficult to use as it is.

3. The message

Every map has a purpose. To construct a map is to express a message. A map without a clear message is a bland map! A map without a purpose is a useless map!

EXAMPLE

This map below highlights the distinction between the dominant socio-professional categories (CSP) in Occitania.

The colours represent the dominant type:

• Red: More workers than executives
• Green: More executives than workers
• Grey: As many workers as executives

The size represent the number of employees

We can clearly identify the communes that group the executives.

4. The public

Constructing a map (choice of words, colors, etc.) also means taking into account the audience it is intended for (children, experts, general public, etc.).

EXAMPLE

This 3W map, specific to the humanitarian sector, identifies humanitarian activities in a country. Its very technical and sector-specific orientation is intended for professionals in the sector, and cannot be used to communicate on actions in a donation campaign for example. It is necessary to adapt the representation and the vocabulary according to the target audience.

Source: OCHA (2017)

5. Simplicity

Too much information kills information! A good map is a simple map that can be understood at a glance.

COUNTER-EXAMPLE

In this map, it is difficult to read any information because of the density of data and the proximity between the type of figures.

You should not hesitate to make two maps or review the data representation to create a simple map.

• In blue : group in progress
• In red: active group

Source: Twitter, Q.Nahelou, 2020

6. Readability

Prioritizing and organizing information is a way to gain clarity and readability.

Be careful with the choice of colors and symbols, both for their readability and their connotations.

COUNTER-EXAMPLE

This map overlays information in close representations (colors, size), making it difficult to read.

Title: Dynamics and trajectories of territories

Legend: Change in the population of communes between 1990 and 2013 (in %)

• Red: Growth +5%
• Green: Stability +-5%
• Blue: Decrease -5%

Size: municipal population of communes in 2013

7. Visual harmony

A map is to be read, but also to be seen, it must be kept in mind that it is a way to make spatial information visible. Guaranteeing harmony in the map makes it easier to read and will make people want to consult it.

COUNTER-EXAMPLE

It is difficult to read this map, which combines several errors, including a lack of harmony in the choice of figures, which complicates the reading and therefore its understanding.

Title: Bas-normands territories referential. Regional frameworks: POPULATION

8. Reproducibility

A map must respect the principles of transparency and traceability by rigorously indicating all metadata: data, sources, methods, dates, etc.

COUNTER-EXAMPLE

Without sources and therefore without information about the data, it’s hard for the reader to get a handle on this map.

Title: Number of factory farms by department.