IGN maps are, like treasure maps, a mystery to most hikers. We reveal the key steps to follow to know how to read an IGN map and make a success of your hike.
Step 1 - Understanding scale and legend
On the IGN maps, published by the Institut National de l'Information Géographique et Forestière, the cover page provides a first level of information. The title, subject, scale and GPS compatibility (for some maps) are all specified. Depending on the scale, the information on the map will be more or less detailed.
For hiking maps, the scale is most commonly 1:25,000. This level of detail makes it possible to indicate the nature and details of the terrain, paths, watercourses, communication routes and relief.
On the institute's website, the scale is defined as follows: "it is the reduction ratio between the cartographic representation and the terrain." This concept allows the length measured on the map to be converted to the actual length on the ground. For a concrete example, refer to the video with mountain guide Florian Olivier, who also provides further explanations on:
contour lines,
spot heights,
the legend symbols, etc.
Step 2 - Knowing how to locate yourself on your map
Next, when out hiking with an IGN map, it is important to know your position on your topographic map.
To position yourself correctly, you will need to draw on your powers of observation and rely on the features around you: watercourses, summits, paths or trails, buildings and other man-made structures.
See more detailed examples in the video below.
Step 3 - Orienting your IGN map correctly
Finally, to make good use of your map in the field, learn how to orient it — an exercise that is not complicated. Especially since on an IGN map, the North indicated corresponds to the left or right edges of the map.
Two options are then available to hikers:
if you have a compass: align a meridian (black line on the map) with the needle of your compass.
if you know your position: identify on the map a point that is easily recognisable in the field, such as a church steeple, a building or a mountain. Then rotate your map while pointing towards the chosen feature. For added reliability, you can check the orientation by sighting a second landmark.
