What are Topographic Maps?

Used to plan routes, track hiking progress, find campsites and water and estimate travel times, topographic maps help hikers and backpackers navigate unfamiliar terrains. These maps show natural terrain as well as man-made structures and are designed to depict the 3D world around us in 2D, including mountains and plains. This is accomplished by using the squiggly flat lines that represent above/below sea level elevations.  Topographic maps represent the topology of a specific area such as mountains, ridges, valleys, plains, rivers and so on. Consider checking out the link to learn more about topographical surveying. 

Known as contour lines, brown lines usually represent a change in elevation of the land, blue lines represent water surface and green lines are a sign of vegetation. Red and black lines on a topographic map are used to represent roads/railroads and show where they begin and end. A topographic map provides an accurate and detailed graphic representation of various features of Earth’s surface including:

• Relief: Mountains, depressions, valleys, cliffs/contours
• Hydrography: Rivers, coastal flats, streams, swamps, and lakes
• Cultural: Roads and railroads, airports, buildings, reserves, borders and administrative boundaries
• Vegetation: orchards, woodlands, etc.

Topographic maps are accompanied by map legends, which list the key Earth features shown on the map and the symbols that correspond to them. Landscape and cultural features such as roads change regularly so topographic maps might not always be up to date. However, since most hikers and backpackers plan on traveling to places far from civilization, they remain relevant in most cases.

Topographic vs. Regular Maps

The main difference between a topographic and regular map is elevation. Most of the elements you find on regular maps such as an arrow pointing towards the north, a scale and legend are also present on topographic maps. But these maps also allow you to determine the elevation and how it changes as you move along the trail. Topographic maps are often used in conjunction with handheld devices such as GPS and smartphone apps, but many outdoorsy people still prefer them in a paper form.

Known as relief maps, these are a type of topographic maps that use drawing and colors instead of contour lines to show changes in elevation. They are useful for people who want a more realistic look of the area to easily distinguish between mountains, valleys, plains and so on just by looking at the map. An example of a relief map is the globe with raised mountain ranges. Topo maps and are also available in waterproof and tear-proof varieties, allowing you to use them in all weather conditions.

How to Read a Topographic Map?

Beginners might find it difficult to interpret what the web of different lines mean in a topographic map, but it’s actually not that complicated. Topographic maps use contour lines, legends and scale to provide a birds-eye view of the surroundings and make it easier to calculate important things such as estimated travel times.

Contour Lines

Points having the same elevation are connected by a contour line, which means following a contour line is like walking at the same elevation (you return at your starting point if you walk it all the way around). Most topo maps indicate the above sea level elevation as a tiny number on some of the contour lines, (US maps in feet, others in meters). Here are some requirements contour lines have to follow:

• They form a closed shape
• All the spots along a contour line have the same elevation
• Contour lines must not cross each other
• Contour Intervals

While many topographic maps indicate the elevation through a tiny number on the contour lines, many don’t have any such thing. That’s because they use contour intervals instead of labeling all contour lines, which can make the map harder to read. Contour lines are often spaced unevenly on topographic maps, which is because the intervals change as the elevation changes.

To determine the contour interval (in order to know the change in elevation), you have to:

Locate two contour lines marked with their respective heights (known as index contour/darker, usually every 5th contour) as well as one or more unlabeled contours in-between

Subtract the smaller height from the larger one and divide the result by the total number of contour lines that are not labeled in-between, and including the next index line e.g. from 5-10, 6,7,8,9 & 10

The resulting number is the contour interval, which represents changes in the elevation.

The value of the contour interval remains constant for all map contours. That’s why you are unlikely to find a single contour line other than in flat areas. More contour lines mean more abrupt elevation changes and vice versa.

Let’s suppose you have two contour lines, one labeled 500 feet and another 600 feet with one unlabeled line in-between. Here the contour interval is 50 feet and elevation at the unlabeled contour line (at any point) is 550 feet.

Topographic Map Scales

Different topographic maps come with different scales and it’s important to know about the differences. Detailed 24K topographic maps are commonly used and are at the scale of 1:24,000 where 1 inch represents 2,000 feet. Also known as 7.5-minute maps, 24K topographic maps cover a latitude and longitude of 7.5 minutes. 100K topographic maps are at the scale of 1:100,000 where 1 centimeter represents 1 kilometer and while they do not offer as much detail as 24K maps do, they cover a much wider area.

How to Get Topographic Maps?

Current and historical topo maps of the US are available as a free download from the US Geological Survey’s official website. While many countries provide topographic maps for free on their official website, for some you might have to dig deeper.

Garmin is another source that offers different topographic maps for sale, while quite a few are also available at Amazon (Camping and Hiking section). Things aren’t that difficult if you are looking for a topographic map in digital format, but finding ones on paper might need some research.

Map Orientation

Orienting a map requires some practice and helps hiker match what’ in front of them to what’s depicted in the topographic maps. This can be useful when determining the current location using a GPS or compass. Even if you don’t have a compass, you can still orient a map by matching the terrain features in front of you with the contour lines.

Estimating Travel Times

The ability to estimate travel times helps hikers plan their adventures, especially if they have to meet other hikers down the road. Similarly, you need to have a time estimate if you want to finish the hike before nightfall as it’s not easy to keep track of trails in the dark. You also need to know the number of meals you’d have to carry to minimize extra weight, which is only possible if you have an estimate of how long the journey would take.

Most hikers are able to cover the leveled ground @ 2mph, but an additional 30 minutes are needed to climb an elevation gain of 1,000 feet. This means an average hiker would roughly need 1.5 hours to cover 2 miles with 1,000 feet elevation gain. The map scale on a topographic map helps determine the distance and estimated travel times. Once you have the approximate distance to travel, you can use the aforementioned average hiking speed to calculate the estimated travel time.

Conclusion

Topographic maps might not be absolutely necessary when following established trails, but they do enhance the hiking experience. The more adventurous you get, the more topographic maps become important. Whether you prefer paper overview, paper detailed or digital topographic maps, they are all very useful, especially when choosing your own adventure. Topo maps help you comprehend the terrain, estimate travel times and get prepared for what’s next.