7.1 The composition of a map
This section is intended to introduce the best practices to incorporate into the layout of a map.
TABLE OF CONTENTS
- The key elements of a map
- The essentials
- The legend
- In addition
A map without a cover is never complete. It is important not to forget these elements and to adapt them to the type and format of your map!
The title summarizes in a few words the information represented on the map, giving the reader useful contextual information. It will remain succinct because it will be completed by the legend, the sources and other information available on the map. It can take the form of a statement, a succession of information or a question, depending on the audience and the use of the map (operational, advocacy, press, …). The title can include the following elements:
- The place, with several degrees of precision according to the scale (Country, Region, Department, Township…)
- The subject intelligible by all (make sure that the acronyms used are detailed elsewhere on the map)
- The date of the represented data
- Milk production in Europe in 2020
- Access to health care in Maputo, Mozambique
The legend is the key to interpreting the information represented on the map. Without it, it is impossible to understand the meaning of the different symbols and colors used on the map. In order to better guide the reader, the legend must be both :
- Comprehensive : all the data on the map must be present in the legend
- Representative: the figures on the map and in the legend must match (same size, same color, …)
- Organized: the data in the legend can be grouped by thematic categories (health, environment, background map …) or by type of figure (point, linear, surface) to facilitate reading
There is no need to display a “Caption” title
The scale is essential on the map since it gives the correspondence between a distance measured on the map and this same distance on the ground. There are two types of scale:
- The numerical scale: this scale is expressed as a fraction (1/25000 or 1:25000) which indicates the equivalence between 1 centimeter on the map and the real distance. It is a scale that can be calculated with GIS software, and is often found in topographic maps.
1:25000 or 1/25000
*Means that 1 cm on the map represents 25000 cm or 250 meters on the ground.
- The graphic scale: this scale is expressed by a line on the map, with an associated distance value. This scale is very useful to have an idea of the distances on the ground
The graphic scale is essential on a map. Indeed, whatever the printing format used, the graphic scale will always be correct since it will undergo the same transformation as the rest of the map. Whereas the numerical scale is only valid for the original print format of the map.
It is important to keep the scale as simple as possible so that it does not focus the reader’s attention (e.g.: talk about 1 km rather than 1000m, preferably in a corner at the bottom of the map…)
If by default the majority of maps are oriented to the North, it is still necessary to specify the orientation of the map. It is often indicated by an arrow to the North. Sometimes the orientation is different, in order to optimize the representation of the study area on the map.
Example with this map of Marseille oriented to the East (see wind rose at bottom right)
The type of arrow used depends on the type of map, but a preference will generally be given to a sober, unobtrusive arrow for all north-facing maps except perhaps for a very illustrative map for which a wind rose would work well.
Any data represented on a map should have its sources indicated. This provides a record of the data used, but also references the author of the data. The reader will then be able to look for more information on these data if he wishes. Open access geographic data are more and more numerous and must always be well cited on the maps.
It is possible to give the source of each data under the legend, or to do it in a dedicated space in the map. The level of precision of the sources varies according to the author or the precision of the data.
The location map helps the reader, in addition to the title, to visualize which region of the globe, a country or a city is represented on the map, by placing it in its general environment. It is particularly necessary when making a map on a local scale (for example, to locate a neighborhood in a city) or a sub-regional scale.
In addition to the source, it is important to indicate for each map its author (generally corresponding to the organization that produced it), as well as its production date to know if the map is up to date.
The list of elements to put in the properties is not fixed but can be adapted according to the needs of the map, the target audience etc. There can be for example: the author, the creation date, the printing format, the confidentiality level
Depending on the type of map being produced, a disclaimer can be included to limit comments on the map, especially when mapping areas where boundaries or names are contentious.
Here is an example of a standard disclaimer that can be used: “This map is for informational purposes only and has no political significance. The boundaries and place names depicted on this map do not imply official endorsement by __.”