How to Prepare an Apple Tart. Part 1

The Art of Cartography in 7 Steps.

Welcome to the fascinating world of cartography! In this article, I reveal all the secrets to creating original and colorful maps.

What are the important choices to make? What should you rely on to make the right choice? This recipe will guide you through the different stages of creation.

Ready to transform raw data into cartographic works of art? Follow the guide!

Part 1: Preparing the ingredients.

In this first part, we will see how to properly prepare all the necessary ingredients for making a delicious Apple Map. From choosing the subject, through projection, and up to data collection, you will know everything about the work required before printing the posters. Let's go!

1. Choosing the right recipe.

What do I want to tell?

Before embarking on the creation of a map, it is important to clearly define the subject it will address. Whether it's a thematic, topographical, or geological map, the subject will guide all subsequent decisions.

For example, city maps show your city's recipe. What are the ingredients that make it up? In what proportion? In short, what makes this city so unique?

For coastal maps, the idea is rather to find all the place names that will revive your memories, a more emotional theme.

2. Preparing your dough well.

A necessary compromise.

Moving from the terrestrial sphere to a flat surface involves compromises and the use of a projection. Each projection has its advantages and disadvantages.

Conformal projections will tend to preserve the shape of countries rather than their size ratio. Equal-area projections will do the opposite and preserve the size ratio between countries at the expense of their shape. Aphylactic projections do a bit of everything, trying to compensate for both shape AND area distortions.

Serving the map's subject.

The choice will be made according to what one wishes to convey. For a navigation map, for example, one would choose an equidistant aphylactic projection that preserves distances from a given point. For a world map dealing with population density by country, an equal-area projection would be more appropriate.

For maps representing small portions of land, such as city maps or maps of the Breton coast, a conformal projection will be used. More specifically, for mainland France, Lambert's conformal conic projection will be used, designed to minimize distortions across the entire country.

3. Selecting quality ingredients.

Reliable and precise sources.

As with any good recipe, prioritizing the quality of ingredients will make all the difference.

For the maps I create, without great originality but with full confidence, I use the databases that cartography and geomatics professionals introduced me to throughout my training.

For all administrative divisions, road networks, and hydrographic features, I favor IGN data, the national institute for geographic and forest information – what could be more reliable on this subject?

Regarding land use data, land-sea boundaries, and coastal toponyms, OpenStreetMap is my favorite. It’s an association that centralizes the work of an ultra-motivated and ultra-committed community on the free circulation of cartographic data and their accessibility to the greatest number. A kind of paradise for cartography.

These two sites offer free downloads of georeferenced data. This means that each shape (point, line, or polygon) is associated with geographic coordinates. Thanks to a GIS (Geographic Information System), I can select the information that interests me from these data files.

Sorting

The amount of data to download per department, which is the smallest division offered, is enormous! To work with this georeferenced data, I use the free GIS software QGIS.

What appears when I open the downloaded files ranges from national roads to the smallest dirt paths, from rivers to the slightest seasonal trickles, from land occupation zones to the smallest buildings...

The 2D modeling of infrastructure in the Ille-et-Vilaine territory by IGN is a 6 GB folder containing 305 files. One file for watercourses, another for water bodies, one for roads, another for built-up areas...

You can therefore easily understand how essential it is to sort through this sea of information. The idea is to always keep in mind the subject and objective of the map to select relevant information without overloading the base map.

The final poster format will also have a significant impact on the amount of information that can be displayed on the map.

4. Preparing your mold.

For the maps I create, I choose very common poster sizes: A4, 30 x 40 cm, 40 x 50 cm, and 50 x 70 cm. These standard sizes allow you to easily find a frame in the material and/or color of your choice. This way, your new poster can harmoniously integrate into your interior decor.

The framing of each map is carefully chosen to highlight the most important elements and avoid unnecessary empty spaces. Attention is focused on the administrative boundary of the city. It must be entirely present within the frame.

This step determines the scale value of the map. The choice of scale allows important details to be seen without losing sight of the subject.

In the second and final part, we will talk about presentation. From color choices to legend creation, everything is always done with one goal in mind: the final legibility of the map!