A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation).
According to Natural Resources Canada,
These maps depict in detail ground relief (landforms and terrain), drainage (lakes and rivers), forest cover, administrative areas, populated areas, transportation routes and facilities (including roads and railways), and other man-made features.
But what exactly does it mean, how to use a topographic map and how Contour lines describe elevation – Today we will try to answer all of those questions.
How to Read a Topographic Map?
There are different kinds of maps that serve different purposes. For example, in order to drive from Point A to Point B, a regular road map will be useful. But once you’ve strayed from the road, perhaps on a backpacking trek or hike, you will need to use the terrain and the contours of the land as reference, meaning that you need to be able to read a topographic map.
So what is the difference between a topographic map and a regular one? Basically, a topographic map allows you to see a three-dimensional landscape on a two-dimensional surface, using the concept of Contour Lines.
Contour Lines on a Topographic Map
To sum it up in one line – the width between contour lines indicates the steepness of a terrain.
Contour lines connect points that share the same elevation, meaning we can walk (metaphorically) on a single contour line and always stay on the same height. When contour lines are close together (they can never intersect), elevation is changing rapidly in short distances – which means the terrain is steep. When contour lines are wide apart, elevation is changing slowly, indicating a gentle slope.
Knowing how to use contour lines on a map is an important skill to have, especially when one is planning a hike of a long trail. For example, when planning a hike – To the Israel National Trail maybe – you can see the routh you plan to take and immediately understand whether it has hills or cliffs which are too challenging to climb.
Contour lines on a topographic map are also important for general navigation. During a hike, you can match the landscape around you to its corresponding contours lines on the map in order to keep track of your location.
Some other concepts to know:
Index lines – Those are contour lines that are thicker, and represent elevatiob which is a round number (for example: 100m, 150m…). At some point along the line you will see its exact elevation is listed.
Contour interval – The change in elevation from one contour line to the next is always the same within the same map. Many maps have either a 40 or 80 foot contour interval. An 80-foot interval simply means that each contour line is 80 vertical feet away from the next closest line. You find the contour interval for your map in its legend.
Depression – A contour line with tick marks inside it indicates a depression, rather than a peak. You should also see elevations decreasing as you get near it.
quick rules regarding contour lines:
- Every point of the same contour line has the same elevation.
- One side of a contour line is uphill and one is downhill.
- Contour lines close to form a circle (or run off the side of the map). The area inside the circle is almost always higher than the contour line.
- Contour lines are drawn close together on steep ground and farther apart on flat ground.
Knowing North
on a topo map, the north will always be at the top edge of the map. You might know other maps that shift north around in order to make the area presented in it fit better on the page. With topographic maps, though, the north will always be in the same place – Up.
Topographic Map’s Scale
The map’s scale tells you how detailed your map is. For example, A 1:30,000 scale means one inch equals 30,000 inches in reality. A larger scale means that a map covers a larger area, but therefore will have less detail. For USGS topographic maps, 1:24,000 is the scale most often used. Maps based on metric units use a scale of 1:25,000, where one centimeter equals 0.25 kilometers.
Other Symbols
Sometimes topographic maps use colors to signify specific features. For example, brown represents the contours of the land, black shows man-made features such as buildings or roads, and blue shows rivers. Sometimes maps will also have purple features, which represents features added after the creation of the map.
Before use, read closely the map’s legend. Start by studying what each line, symbol and color means. Generally, green symbolizes vegetation (forests, fields) while blue represents water objects (streams, lakes). Darker colors mean denser objects, while light or colorless areas suggest open terrain.
Did you know?
One of the first uses of topographic maps was in the eighteenth century when the British military carried out detailed surveys of land.
The United States military followed suit and also used topographic maps for tactical strategies — there was even a “Topographical Bureau of the Army” during the war of 1912. Pioneers in America also used and created topographic maps as they began to explore more of the country and expand their geographical knowledge of Western America.
How to improve
Want to learn more? Practice makes perfect!
You can practice reading features from a map of a familiar area. Try and visualize how the terrain you see relates to the contour lines on your map, use visible features like peaks and passes and try to Identify the subtler features.
If you can get in the habit of checking your map every time the elevation or landforms around you change, it becomes very easy to keep track of your location on a hike, regardless of where you are.
For further reading on this topic (and more), we can recommend Wilderness Navigation: Finding Your Way Using Map, Compass, Altimeter & GPS.
This book, which is a best seller, is the official navigation textbook used in outdoor education courses by thousands of students. It will help you master map and compass skills, which is the foundation for traveling safely in the wilderness.
