#101 Navigation

Far from our usual reference points, knowing where you are and where you are going is an important skill to acquire for anyone who loves the outdoors. With no signs, no roads and no passers-by to ask for directions, a sense of navigation is essential if you don't want to get lost. Navigation is the technique of planning, keeping and finding your way again. From here on, we will break this skill down into two categories: strategic and tactical. Strategic navigation is the technique used to define the route you will have to cover on the ground. Tactical navigation, for its part, is the technique used directly in the field to follow the path travelled or to find it again. Before detailing these two categories, the topographic map — the essential medium of all navigation — deserves an introduction.

The topographic map, the foundation of navigation

A topographic map is the projection of a three-dimensional environment onto a two-dimensional medium. That medium is either a screen or paper. This projection requires a set of devices so that you can find your bearings in it. These tricks will let you visualize the features of that environment — relief, forests, meadows, rocks, cliffs, marshes and so on — and their positions relative to one another.

The way a map's dimensions are displayed is codified to make reading easier. To decode the data, you then need to turn to the map legend, which details the different visual conventions.

The legend tells you which type of line corresponds to which type of trail or road, lets you determine what kind of terrain is drawn according to the colour used, and helps you identify geographic landmarks (a church, a water point, high-voltage power lines and so on).

The topographic map then lets you position these elements (terrain, trail, etc.) relative to one another, using a scale and contour lines. The scale tells you the equivalence between a distance measured on the map and a distance measured in the real world. This scale can be numerical, for example 1:25,000, or graphic, by drawing a segment on the map and indicating its ground equivalent. In the case of a numerical scale, a so-called 1:25,000 map indicates that the distance measured on the map corresponds to that same distance multiplied by 25,000 in the real world. 1 centimetre on the map equals 25,000 centimetres on the ground, i.e. 250 metres. The larger the scale, the less locally precise the map will be. In some cases, the scale is given as the equivalence between a paper distance and the ground distance (particularly for digital maps).

Most digital maps let you measure distances quickly using dedicated tools. Paper maps are in most cases overlaid with a grid of identically sized squares, ideal for quickly calculating a distance by comparing it with a reference distance. Some paper maps also let you quickly identify the distance between two points on a trail.

That said, a map's precision is not only tied to its scale, but also to its content. IGN maps are rich in information, but that is not a constant across map makers. Some 1:25,000 maps are far less useful than 1:100,000 maps. Large-scale maps also have the advantage of offering an overall view of a route, whereas it would take four 1:25,000 maps to cover the same area. Contour lines are used, in addition to the scale, to draw the third dimension. They represent the altitude of every point on the map without leaving it cluttered and unreadable. Lines are drawn to indicate altitude increments: a line will, for example, indicate that every point lying on that line is at the altitude corresponding to it. This magnificent invention lets you quickly visualize the altitude of every point, but also the shape of the terrain, and highlights its distinctive features.

Contour lines most often come in two representations. You will find thicker lines to highlight major altitude increments (such as every 50 metres in the example above), then thinner lines to mark finer increments (every 10 metres in the example above). Take the example of a perfect cone. To draw the contour lines, you slice this cone into layers of a fixed thickness. Each contour line is then drawn to define the outline of that slice. All that remains is to superimpose the lines to get the final representation. Learning to read a map means learning to recognize the combinations of lines that indicate the presence of a pass, a summit, a cliff, and so on. The closer together the contour lines, the steeper the slope.

With experience, contour lines let you quickly identify summits, passes, drainages, and more.

Now that we have covered the topographic map, on to navigation.

Strategic navigation

Strategic navigation is closely tied to the preparation phase of your outing, since it is where you study the possible routes. It notably consists of establishing:

1. the route of the outing
2. the geographic landmarks that can serve as references
3. the bail-out routes.

The route is, to put it simply, the line on the map that you will follow during your trip, combined with a progression schedule, the identification of camp spots, resupply points and dangerous areas. The progression schedule becomes possible once the route is chosen, by measuring the distances and elevation gain of the outing on the map. This schedule gives an idea of the time needed for the progression and of the physical difficulty level of the route. The route will also allow you to establish the technical difficulty of the course. Geographic landmarks are objects that are easily identifiable on the ground and let you quickly position yourself on a map. These key points can be summits, churches, watercourses, roads, etc. Once in the field, it then becomes easier to orient yourself knowing, for example, that your heading is correct as long as that summit stays on your right. Bail-out routes are changes of itinerary in case of difficulty (injuries, bad weather, etc.). The simplest bail-out route is to retrace your steps. That said, it is sometimes shorter to take another route to get back to civilization (villages, roads, etc.). These bail-out routes must be worked out just as thoroughly as the main route. This greatly helps decision-making in the field, especially when the situation is stressful. The first step in defining your route is to go looking for information on the outing you have in mind, ideally from several sources. These sources can be blogs, trip reports, route guides available on collaborative sites, guidebooks, etc. The Lonely Planet and Guide du Routard guides let you quickly gain a general picture of a region and the very broad specifics of the route. They are nevertheless far from sufficient for defining a solid itinerary. This information can be supplemented by consulting the websites of agencies offering the trek or its equivalents. But it is trekkers' accounts that will be the richest in information. Nothing beats a query in a search engine to find the right blogs. The French-language sites camptocamp.org and randonner-leger.org are also packed with interesting information. Don't forget video-sharing sites, or checking the right hashtags on social media. During this research, the ideal is to get your hands on GPS tracks (in GPX, KML or KMZ format). These files let you visualize a route on a digital map. But great caution is called for regarding the match between this virtual route and the real one. All the more so since it is possible to generate GPS tracks without ever setting foot on the terrain. Good practice is to treat every track as if it had never been confronted with the terrain, and to rework it accordingly. GPS tracks are very interesting because they quickly give you the distances and elevation gain. They are also used by GPS devices for tactical navigation. Once you have determined your route, you still need to save it. The simplest solution is to make yourself a table on a sheet of paper, noting for each day:

• the starting point;
• the end point;
• the distance and elevation gain (positive and negative) to cover;
• the geographic landmarks;
• the potential bail-out routes.

Ideally, you will also note which map to use for the day, and mark the route to follow on that map. The most robust solution is to add a GPS track (or several tracks, if you factor in the bail-out routes). Gaia GPS is a platform that lets you create, from a computer, a syncable and shareable folder that will contain notes, photos, and all the tracks and geographic landmarks. This folder can be synced to your smartphone for offline use. These folders can also be shared and opened to contributions from other users, to prepare a route as a team. Other apps also offer more or less similar services. Finally, it is also in this preparation phase that you will need to identify the areas populated by wildlife. In particular, identify bear areas, moose areas, etc. so you can adapt your behaviour once in the area in question.

Tactical navigation

Tactical navigation is the navigation carried out directly in the field. It can be done effectively either by using the compass + map pair, supplemented or replaced by one or more GPS devices. When you are progressing by climbing on rock, navigation will be done using a route topo and your experience. On a glacier, navigation will be done directly by reading the ice and using basic glacier travel skills. Nevertheless, one system that suffers neither bad weather nor battery failure is your sense of direction. A sense of direction is above all a sense of observation. Many people think it is an innate gift, but these senses are trained with experience. You just need to be proactive in your navigation and open your eyes to your surroundings. You can, for example, note the presence of cairns or rocks near the trail, count the number of watercourses crossed, spot trees with unique shapes, etc. You can also turn around from time to time during the progression to familiarize yourself with the path in the opposite direction. A good sense of direction lets you at the very least retrace your steps and, for more experienced people, understand the logic of the terrain. A GPS device lets you read a GPS track, and therefore know at every moment your position relative to that virtual route. Technology being what it is, the GPS track should nevertheless be treated as general guidance. You have to know how to be very careful in the field, particularly in rugged areas, so as not to get caught out. A GPS has at best an accuracy of one metre in the ground plane. One metre in alpine sections or on a glacier is sometimes a lot. The only tracks you can trust are the ones you are currently recording. By combining your memory with that fresh track, the level of confidence in the track for turning back is very high. Recording your progression is very useful in foggy conditions, when visibility is very low. In those conditions, if you have no GPS device or are unsure of yourself, the best way out is to wait for those conditions to clear before getting moving again. GPS is the future of tactical navigation. However, knowing how to use a compass and a map to orient yourself and follow your progression is a mandatory skill for an outdoor professional. The compass and map pair is used to triangulate your position. This triangulation rests on the fundamental assumption that you are holding a map covering the terrain you are on. To this first part of the triangle are added two straight lines drawn between your position and two reference points on the horizon. The two reference points can be passes, summits, etc. whose names you know and which are visible on the map. The steps to position yourself on the map with a compass are as follows:

1. Orient the map: make the map's true north match the terrain's true north.
2. The map's true north is indicated in the legend, and most often corresponds to the top of the map when it is oriented so that you can read the text.
3. The terrain's true north is to be identified with a compass, by measuring magnetic north (the north given by the compass) and applying the magnetic declination indicated on the map (true north and magnetic north are distinct and several hundred kilometres apart).
4. Spot two reference points on your horizon line. The further apart the points, the larger the angle formed by the two lines, increasing the accuracy of the positioning.
5. For each point, take the bearing and transfer it onto the map:
6. hold the compass flat at eye level. Turn the inner (round) part so that it aligns with magnetic north, then align the outer body so that it points towards the reference point. You thus obtain a bearing relative to magnetic north.
7. adjust this bearing by the magnetic declination in order to get a bearing relative to true north. An arrow on the compass's inner dial lets you keep true north marked on the compass.
8. transfer this bearing onto the map: align the true norths of the compass and the map. After placing the long edge of the compass on the reference point, all that remains is to draw a straight line.
9. Your current position is at the intersection of the two resulting lines.

The greatest difficulty is correcting the bearings properly for magnetic declination, and above all identifying in which direction to correct them. To get more comfortable, nothing beats regular practice of the method. It is then possible to follow your progression by repeating this locating method over time. Nothing beats orienteering races for sharpening your technique. Not all GPS devices have a base map. No matter: you can use a GPS position to find where you are on a paper map. Modern maps carry longitude and latitude information along their edges, to be compared against the measurement of a GPS point. Be careful, though, to use the same unit: the most common are UTM and WGS84 coordinates. Before projecting yourself onto the map, simply check which unit your device uses. This technique will nevertheless be less precise than with a compass, as the GPS grid on a paper map remains coarse.

Nowadays, the compass + map pair is less and less attractive in the field. Phone apps, dedicated GPS units and mountain watches are increasingly reliable and feature-rich. Of course, a compass and a map require no power and never crash. But a map in the rain has a very limited lifespan, and if you are truly lost and without a reference point, the compass can prove hard to exploit. By multiplying the electronic devices used for geolocation, you guard against possible failures. Setting out with three GPS devices is a simple redundancy solution: a mountain watch, a phone with the Gaia app and an InReach GPS (plus an external battery if recharging is needed). Two devices can thus record the progression at all times. The third is used in case of serious trouble. The probability of all three failing is fairly low. Not to mention your sense of direction, which will at the very least let you retrace your steps. Tactical navigation can be made more difficult by weather conditions, which hinder the identification of your surroundings, and by the physical condition of the navigator. Fog is the worst time to navigate, in the sense that nothing is visible and it is hard to correlate your assumed position with your actual position. Snow can also catch you out by masking watercourses or small terrain features. As for physical condition, it is important to understand that navigation places a heavy load on the brain, which quickly tires the body. Navigating while tired is a source of errors; do not forget that in your decision-making. Finally, do not let yourself be intimidated by the pressure of a group when you are the navigator. A good tip is to involve the other members in the decision-making. To finish, a few other points to consider:

• In the field, carrying precise paper maps no longer really makes sense, except on short outings or for very complicated environments. Using a topographic app on your phone or GPS lets you get an idea of where you are and what lies ahead, without needing to carry 15 maps. A map with a larger scale, on the other hand, is useful for getting an overall view of the route and of the distance still to cover, and for identifying bail-out routes when the need arises.
• Tactical navigation at night is much easier when you have a powerful light source (\> 200 lumens).

The tools needed for navigation

Strategic navigation

In addition to guidebooks, blogs and other written resources, navigation relies on maps. Paper maps are far from all being equal. In France, practitioners are lucky to have high-quality IGN maps, with precise and detailed terrain information. As soon as you travel, however, things already get more haphazard. The ideal is then to get your hands on several maps from different brands, but representing the same terrain. Cross-checking the data increases precision. At the time of purchase, check whether the map has a legend, a scale, the magnetic declination value, the orientation of north, as well as a GPS grid in a unit usable with your GPS devices. Several mapping solutions are available on the web. Among the most complete, Gaia GPS is a reference in the field. It is a mapping platform accessible from its website and dedicated apps on iOS and Android. I have not tested every existing solution, but the Gaia GPS smartphone app is stable and demands little battery even when recording your progression. With this tool, you can prepare your strategic navigation from the website, then sync it with the smartphone app to be ready for tactical navigation. You can also record your route, as well as geographic points of interest (and attach photos to them), which will be synced with your web account once back in network coverage. Gaia GPS also has several base maps, with a worldwide base layer already quite rich in information. IGN maps are accessible from Gaia GPS. The only major drawback is that this solution is not free. The subscription is nevertheless quickly paid off for anyone who gets out in the field a lot. The Google Earth program is also very interesting for visualizing your route in three dimensions. Google Earth projects satellite images onto a 3D terrain model to simulate the terrain. No more need to read contour lines, then. The program also lets you measure distances and elevation gain. But a big flaw is that this program can only generate GPS tracks in KML or KMZ format, and you will have to go through online converters to convert them to GPX, usable by a GPS device.

Tactical navigation

For tactical navigation, a complete kit includes a paper map, a compass, a pencil, as well as one or more GPS devices. The compass is a passive device consisting of a magnet used to “read” the Earth's magnetic field. The magnet generally takes the form of a needle free to rotate, placed in a shallow cylinder filled with a liquid to limit friction. There are many different models, but the most effective for positioning are those equipped at minimum with a plate that can rotate relative to the cylinder. Markings on this plate let you point at a potential reference point, draw a straight line and have a scale conversion at hand to make distance measurements easier. Some high-end models also carry a mirror plate that folds to 90° from the previous plate, thus allowing better sighting towards the horizon. Others also allow reading in the dark through the use of phosphorescent parts, but do not forget that navigating at night is a real challenge, especially for identifying reference points.

Note that some compass models are only certified for one hemisphere, generally the north. This is because the Earth's magnetic field lines, on which the compass needle aligns itself, point underground at the north and south poles (and not along the surface). In the northern hemisphere, the north end of the compass is therefore pulled downwards. To compensate for this phenomenon, the south end of the compass needle is slightly weighted. When you use a “northern hemisphere” compass in the southern hemisphere, the south end of the needle is pulled downwards by the magnetic field, even though it already carries a counterweight. As a result, the south tip of the compass catches on the bottom of the cavity in which it is housed, and therefore works much less well. Since the beginning of this article, we have been talking about GPS in its everyday sense. In the technical sense, GPS is a constellation of satellites enabling geolocation on the surface of the globe to within about 1 metre at best (and 25 m in altitude). The GPS constellation is not the only one. It shares space with the Galileo, Glonass and Baidu constellations, respectively European, Russian and Chinese (together forming the GNSS). When acquiring a GPS device, favour compatibility with as many of these constellations as possible and learn to recognize the performance and reliability of each of them depending on your position on the Earth's surface. A GPS device is a portable unit fitted with an antenna compatible with one or more GNSS constellations. A GPS unit is a device that, at the simplest, lets you read your GPS position, up to being able to locate yourself on a base map, record your position and navigate around a track or points of interest. The more expensive models are rich in tracking and search functions, and come with more pleasant ergonomics. In this field, Garmin has managed to crush all the competition in recent years, notably with its Garmin eTrex models.

To the functions of the basic GPS is added satellite communication. You then end up with devices which, in addition to the classic GPS functions, can share a position with the outside world, retrieve weather forecasts, communicate via message with your contacts or alert the rescue services. The best-known devices are the InReach units from the late DeLorme (bought out by Garmin) and the Spot units from Globalstar. Just as with the GPS constellations, it is essential to check the coverage of the constellation dedicated to communication.

The mountain watch is one of the most popular solutions among practitioners. These devices carry an electronic compass, a thermometer and a barometer to measure atmospheric pressure. These sensors make it possible to estimate a weather trend, as well as an altitude. More and more watches have a GPS antenna to follow a track or record your progression. The most complete models also carry a battery sufficient for several days of use, a heart rate sensor to place on the chest, and an optical sensor at the wrist to measure heart rate (less precise than the chest sensor) and blood oxygen saturation.

These watches are a must-have for the modern mountain athlete. On top of their GPS capabilities, the ability to pair a heart rate strap makes them the ideal training monitor. The best-known brands in the mountains are Suunto, Garmin, Polar and Coros. Finally, a very useful tool: PeakFinder is an app available on iOS and Android that lets you identify the surrounding summits from your GPS position. This app can be used without a network connection, provided you have downloaded the identification data beforehand. More information at https://www.peakfinder.org/fr/mobile/.

Attached document — available on this page soon.