Contour lines are lines drawn on a map that connect points of the same elevation. Stack enough of them together and a flat sheet of paper starts to show the shape of a hill, a bluff or a valley. This guide explains how to read them, using the designs on our topographic map gifts as examples.
The short definition
The U.S. Geological Survey describes elevation contours as imaginary lines connecting points that have the same elevation, measured from mean sea level. USGS also notes that contours make it possible to show the height and shape of mountains and the steepness of slopes. That is all a contour line is: a level path traced around the land.
Picture walking around a hill without going up or down. The path you trace is one contour. Step uphill a set amount and walk around again, and you have the next line. Repeat until you reach the top, and the result is a set of nested rings.
Four things to look for
1. Spacing tells you about steepness
When lines crowd together, the elevation changes over a short distance, so the slope is steep. When they spread out, the ground is gentler. On a ski hill design such as Big Powderhorn Mountain you can often spot the steeper faces simply by where the lines bunch up.
2. Closed rings usually mark a high point
A small closed loop at the center of a set of rings is typically a summit. Isolated hills, such as Bear Butte, tend to read as a tidy bullseye because the land rises on every side toward one top.
3. V shapes point to valleys and ridges
Where contours cross a stream valley, they bend into a V or U shape. The point of the V aims upstream, toward higher ground. Ridges make the opposite pattern, with the bends pointing downhill. Bluff country, like the places in our Driftless Area collection, is full of these crinkled lines.
4. Wide flat areas look almost empty
Flat ground gets few lines, because the elevation barely changes. Lakes, river bottoms and prairie show up as open space, which is part of why a hill rising out of flat country makes such a strong design.
Contour interval and index lines
The contour interval is the elevation difference between neighboring lines. Printed survey maps state it in the margin, and they usually draw every fifth line heavier as an index contour, labeled with its elevation, so you can count up or down without losing your place.
Choosing an interval is a trade-off. Too small, and a tall or steep place fills with so many lines that they merge. Too large, and gentle terrain loses its shape. For decorative designs, the interval is picked so each place reads clearly at gift size rather than to match a printed survey sheet.
How this shows up in our designs
Each design on Map Gift Store is drawn from U.S. Geological Survey 3D Elevation Program data. We describe the process on how the maps are made, and our post on 3DEP elevation data covers the source in more depth. The designs keep the contours and leave out roads, labels and trails, so the land itself is the subject.
Because they are art rather than survey maps, the designs are not meant for navigation. They are meant for the person who already knows the place and will recognize its shape on a shirt or a print.
A few shapes worth comparing
- A high point with steep sides: Black Elk Peak, the top of the Black Hills.
- Long bluffs above a big river: Grandad Bluff in Wisconsin.
- A range of old, rounded knobs: Taum Sauk Mountain in Missouri.
- Sand dunes above a lake: Sleeping Bear Dunes National Lakeshore in Michigan.
Looking at them side by side shows how much the spacing and shape of the lines change from one kind of landscape to another, even though every design follows the same rule of equal elevation.
Reading a design before you buy
When you open a place page, look first for the highest ring and the tightest spacing; that is where the drama is. Then check the edges. A design that runs to a lakeshore or river will flatten out at that side. If you are buying for someone, ask yourself whether they would recognize that outline from the trail, the chairlift or the car window. Usually they will.
Products are printed to order, and final price, sales and shipping are shown at checkout. You can browse every format on the gifts page.
Frequently asked questions
What does a contour line on a map show?
A contour line connects points that sit at the same elevation. Follow one line around a hill and you stay at one height the whole way.
Why are some contour lines close together and others far apart?
Spacing shows how quickly the ground rises. Lines bunched together mean the elevation changes over a short distance, which reads as a steep slope; wide gaps mean gentler ground.
What is a contour interval?
It is the change in elevation from one line to the next. A small interval adds detail on gentle terrain, while a larger interval keeps a tall, steep place from turning into a solid block of lines.
Can I use a contour design from your shop for hiking or navigation?
No. Our designs are decorative art made for gifts. They leave out trails, roads, labels and other details a real map needs, so carry a proper map for any trip.