Frown Shaped Contour Lines Mean Down
When I was learning how to read topographic maps, I developed a little memory heuristic to help remember the difference between contour lines that were going uphill versus those that were descending. I shared this with a hiker on one of my backpacking trips recently and it really helped them understand what the lines mean on a topographic map, so I thought I’d pass it along.
When you walk toward a frown, you go down
Let’s look at an example. This is a topographic representation of a hill. If you walk in the direction of the red arrow, you cross contour lines that are shaped like a frown, which frequently means you are going downhill.
Now, let’s look at a landscape and then a real map to demonstrate how to use this heuristic in practice.
Mount Lafayette and Eagle Lake, White Mountains
This is Mount Lafayette in New Hampshire and here’s the topographic map for it from the National Geographic Topo DVD.
Descending Mt Lafayette
If you walk in the direction of the arrow, you will intersect contour lines that are shaped like a frown. While you’ll often be going downhill when this happens, you should still check the elevation markings (numbers) on the contour lines to see if they are descending or ascending, to be sure.
Ravines
This is a case where you can descend from higher ground and not encounter a frown shaped contour line on a map. If you are descending into the head of a ravine, the contour lines won’t look like a frown but will be v-shaped. Take a look at this example below. This area is called Eagle Ravine and it’s a very steep avalanche zone on the northwestern shoulder of Mount Lafayette.
Not a frown, but still going down
As you can see, the contour lines at the point of the V shape are very close together which indicates a steep elevation grade. If you trace the contour lines out from the point of the V you’ll see that they are frown shaped as they approach each other, although it’s a little harder to see their curve until you move father away from the point where they intersect.
This isn’t really a contradiction to the frown is down rule of thumb because there are downhill gradients (and frowns) on either side of the V, but it does highlight the care you need to take when interpreting contour lines that are flatter and less curved, when reading a topographic map.
Lakes and Valleys
If you’re standing at a low point in the landscape like a lake that is surrounded by hills, the frown is down heuristic doesn’t always work if you start walking uphill. Let’s look at East Pond, which is located just west of Mt Osceola in the White Mountains, for an example of this.
East Pond
In this case, if you walk in the direction of the arrow, you will be crossing frowns but going uphill. You can determine this because the 3000 foot contour line is outside or beyond the 2800 foot contour, indicating an ascent if you walk in that direction.
East Pond
Here’s what East Pond looks like, to help you match the symbols on the map to the actual landscape. As you can see, the landscape forms a saddle between two high points. The best advice I have to give in situations like these is to be sure to check the contour elevations when reading your map, to double check your interpretation of the topographic map you’re using.
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In the first example–if the contour lines represented a sinkhole rather than a hill, "frown-is-down" would be wrong. I think the easiest way to see whether you are going up or down is to just check the elevations of the major contour lines you are crossing. I can see how "frown-is-down" could help provide some intuition, but I'm not sure of its practical use in the field.
If it were a depression, then the frown would have teeth. Walking into man-eating frowns is bad. Well, maybe not bad, but opposite.
True, Blitzo, but in all the maps I've used, Sarlaccs are indicated by a special symbol
Alex – you'd think so,but beginners don't perceive the mass of symbols on a map like a more experienced map reader does. I didn't and the person I was teaching didn't. It can be very hard to remember what it was like to be a beginner – people really do have an amazingly hard time figuring this stuff out/or may be far less visually adept than you are.
In addition, the numbers may be hard to see because the slope is so steep or because the printer located them some distance away from the point of your descent. What you really need to do is to internalize a feel for the undulations of the landscape around you, rather than focus on the numbers. Height is irrelevant when you're walking; slope contours are what count.
A Sarlacc – had to look that one up – a creature from star wars. http://starwars.wikia.com/wiki/Sarlacc
Hey Earlylite,
I agree with you–and didn't mean to come off as a know-it-all. I'm only saying that I would be cautious about teaching a heuristic that is wrong in a lot of circumstances. I think it might end up being a crutch in the end.
No worries. So where's it wrong? I tried coming up with counter examples before writing this up and couldn't think of any more. Seriously, I'd really like to know where the heuristic fails so I can document them.
In my first comment there was a counter example. If the smallest contour in your drawing was actually the lowest elevation, you would be in the bottom of a big pit and need to walk up–through frowns–to get out.
In the real topo, the only reason you know Mt. Lafayette is a mountain and not a depression is because it is labelled and the major contours show the elevations rising to the summit.
(Sorry if this is posted twice–it didn't seem like the first one worked)
Ah yes – I see what you mean. Yep the numbers do matter. Thanks. I'll amend the post to include that point soon. – probably worth emphasizing a bit more!
(Your comment came through – it just got trapped by my spam filter because it had a link in it.)
This is a tough one to teach to scouts. We always point out to look for the water, because it always goes to the lowest level. If the high points aren't obvious, then work from the bottom up.
Crater Lake would be a prime example. Here in Virginia, Burkes Garden (37.1004, -81.338, also referred to a God's Thumbprint) is a large feature several miles long where the frowns go down on the outside and the smiles go down on the inside, but there are still some small streams to differentiate the highs from the lows.
Alex & Rev – thanks for catching that one guys. I think it's fixed now with a good counter example.
Easiest way to teach, I find, is to have a drawing like yours with the circles, and the same available as discs cut out of thick cardboard. Then you can stack the cardboard discs to build a 3D topo model. And everybody goes "Aaaah". Then, you show the contour lines of a ravine V, and again have the cardboard V's handy to stack into a 3D model. Everyone goes "Aaah" again. From there, I can usually move on to explaining the numbers and lines, without needing the 3D props again.
I'm actually a geographer so I don't have a typical angle on this, but you're just wrong. You can easily walk uphill towards a frown. Walking up a valley will walk up a frown. This is only true when on simple hills and ridges.
For the lay person, topos with 2.5D contour shading is helpful. Or you could just teach them how to read a map. It's really not that hard.
I think we established that in the previous comments, and I added the final qualifying paragraph to provide an example. Thanks for reiterating it though.