Orienteering is the ability to use a map and compass to identify your location and plot a course to a specific destination. In urban areas, map reading is pretty simple; just match the street names to your view, and you can easily find your way from A to B. This is one of the most essential survival skills.
In the wilderness, though, there are no handy street signs, so you have to start with big, obvious landmarks such as specific mountains and do some compass work to determine both A and B. Sometimes, that will require using a type of map you may be unfamiliar with.
Topographic maps, also called topo maps or topo sheets, are two-dimensional representations of three-dimensional landscapes. On topo maps, each point that is at an equal elevation is connected by a contour line.
A line is drawn to designate a specific change in elevation (usually every 40 or 80 feet, but any number may be used). This is known as the “contour interval,” and each topo sheet will list which interval it uses. Some contour lines are thicker than the others and have their exact elevation listed on them.
These are called “index contour lines,” and are usually spaced five lines apart. Contour lines never intersect, so the map is filled with nesting “blobs” that show the shape of the landscape.
Contour lines that are close together indicate rapidly changing elevation (steep terrain). Conversely, contour lines spaced farther apart represent gentle slopes.
Topographic maps may also include latitude and longitude designations, the names of geographic features, the scale at which they are drawn, their declination (more on this later), and other important information. Look for a legend that illustrates which data is included on the map and how to interpret the various symbols and colors it uses.
Topo sheets can also indicate negative elevation, as when displaying craters or other dips below the base elevation. In these cases, the contour lines have tick marks inside them
It may be difficult to make out, but the contour lines in the middle all have tick marks on them, indicating that this is a depression rather than a rise. You will also notice that the index contour line in the center circle has a smaller number than the other lines, which means it is at a lower elevation than the surrounding terrain.
It takes some time to learn how to read a topographic map. The best way is to get one for an area you know well and practice lining up familiar landmarks to see how they are represented on the map.
Essential Survival Skills: Choosing the Right Compass
Modern compasses have a lot of features that are crucial for orienteering. In order to use a map correctly, your compass should have the following:
- Magnetized Needle – Most are painted red on one end to indicate magnetic north. They are typically encased by a non-freezing fluid that steadies the needle movement.
- Rotating Azimuth Ring – This ring has degree markings from 0 to 360 and is used to take bearings.
- Transparent Baseplate – So you can read the map through it.
- Orienteering Marks – A variety of directional lines, reference points, and rulers to assist in navigation.
- Declination Adjustment – Declination is the difference in degrees between magnetic north and true north, and it changes from region to region. These also change over time, so be sure your map is up to date. You can visit the NOAA site to get current declination listings. Adjusting for the local declination will ensure you are taking true readings.
Extra compass features may include:
- Magnifier – To make map reading easier.
- Luminescent Marks – To make it easier to read your compass in the dark.
- Sighting Mirror – Assists in aiming at distant landmarks, and can be used as an emergency signal.
- Inclinometer – Also called a clinometer. It measures the grade (steepness) of an incline or the height of distant objects. Helpful if you are evaluating the possibility of an avalanche.
- Global Needle – Compasses are North- or South-America specific. A global needle ensures correct operation worldwide.
NOTE: Novelty compasses, such as those that attach to a zipper pull, are fun (and again, better than nothing), but they are not a substitute for a real navigational compass. Even digital compasses like the ones you see in an app store lack the features you’ll need for orienteering.
Map and Compass Navigation
Now that you know how to read your map and have the right kind of compass, you can use them together to navigate. The steps are:
- Adjust for local declination (see above)
- Place your compass on the map so the Direction of Travel indicator (typically a small triangle) points to the top of the map. Align one edge of the base plate with the edge of the map.
- Holding the map and compass, turn your body until the needle lines up with the orienting arrow.
- You are now oriented correctly and can use landmarks to navigate.
If you know where you are on the map, you can use a bearing to get to a destination. Keep in mind that bearings are always relative to a specific starting point. People at different places will use different bearings to get to the same destination.
- Set your compass on the map so one edge of the base plate lines up between your current location and your destination. The direction of travel arrow should point towards your destination.
- Rotate the azimuth ring (NOT the compass itself) until the directional lines behind the needle aligned with the north/south grid of the map (or the left and right edges).
- Read the degree marking at the index line. That is your bearing.
- Without the map, point the direction of travel arrow away from you and turn your body until the needle is within the orienting arrow.
The direction of travel arrow is now aligned with your bearing, and you can follow it to your destination.
If you don’t know where you are on the map, you can use the compass and map to find out.
- Point the direction of travel arrow directly at an identifiable landmark.
- Rotate the azimuth ring until the needle is within the orienting arrow.
- Read the degree (bearing) at the index line.
- Place your compass on the map and align an edge with the landmark. The direction of travel arrow should roughly point towards the landmark.
- Rotate the base plate until the directional lines align with the north/south grid, and the North marking on the bezel points to the top of the map.
- Draw a line along the straight edge from the landmark to your trail. You are located at the point at which the line intersects the trail.
- If you aren’t on a trail, repeat these steps using (ideally) three landmarks that are at least 60 degrees away from each other. The intersection of these lines, or the small triangle they create, will identify your location. This is known as triangulation.
We hope you have found this post to be helpful. Remember, orienteering takes practice to get good at it. Start with familiar areas to get the basics, then slowly increase the challenge. There are orienteering clubs all over the world that use these skills in races; perhaps there is one near you.
Tomorrow, we will be discussing what to do in case of an earthquake. We look forward to seeing you there!