10 Things to Know — Part 7: Read That Topo


Post by WildSnow.com blogger | September 27, 2007      
Map reading.
Chris Clark map reading on the Trooper Traverse

It’s the days of GPS, but in most cases you still need to read a map. Indeed, even with a GPS you may have a topo map showing in the display and you need to school your mind on how to interpret all those squiggly lines and stuff. Problem is, with guides, marked trails and yes, GPS, we get less and less practice on basic map reading. Apologies to experts out there, this is written for people just starting with map nav.

Reality is that reading a topo isn’t all that tough. What helps is sticking to the basics. Here it is in steps.

1. Get a practice map, USGS 7.5 minute, 1:24000 scale. If those numbers look like gobbledygook don’t despair, you’ll understand them soon enough. A map of your area will work if you live near some natural landscape. WildSnowers say that city folk should get one of their favorite hiking spot or somewhere else in the country they go frequently. Get a full sized printed topo if you can, from an outdoor store or map outlet. You can print topo maps from a variety of sources such as software packages and websites like Topozone.com, but you’ll usually end up with an 8 1/2 x 11 map, and that doesn’t cover enough area for good learning visualization of how these things work. If you print from the web or software, do multiple prints and make a “tile set” you tape together.

2. Figure out what the directions are on the map. You know that up is north, correct?

3. On your practice map, identify some terrain features that require lots of those squiggly contour lines. By taking a few walks, learn to compare how those lines look to the actual landscape. At the same time you’ll learn how different features are marked, such as roads and streams. For learning this you can find tons of help on the web, just google it.

4. Obtain a small, easily carried compass with a clear rectangular base, such as the Brunton Classic.

5. While map experts frequently operate without a compass by comparing their map to terrain features, you can jumpstart your map reading with compass use. The thing to remember about this is for map reading you generally use a compass to match the map to the terrain so you can visualize your route. Other times you may use the compass to point your direction, but here at WildSnow.com we’ve seen this is less common for backcountry skiing and now more easily and better done with a GPS.

Map reading.
North arrows from USGS map, they look confusing. Just line your compass needle up with the one marked “MN,” as that’s magnetic north.

Using a compass is relatively straightforward, with one glitch. The needle points to the magnetic pole of the earth, but geographic north on the map is slightly different. While all sorts of memory tricks exist to help deal with this, here is the foolproof way: Look on your map for a set of north arrows. On regular USGS 7.5 minute maps this is on the bottom map margin, as it is with many other maps. One arrow will line up with the top and bottom of the map, and may be labeled “GN” or “Geographic.” Another arrow will still point up to the top of the map, but will point to the side of the GN arrow. This is the magnetic north arrow and may be labeled “MN” or “Magnetic.”

Simply hold your compass over the map arrows (that’s one reason you use one with a clear base), and rotate the map till the MN arrow on the map lines up with the compass needle. Now your map is “oriented.”

The training is over, on to actual tips.

1. For any mountain navigation you should have a barometric altimeter in addition to your map and compass. Good quality wrist watch units work fine as do GPS units with a barometric altimeter, but learn how to calibrate your chosen instrument. Calibration means manually changing the elevation reading to match that of your location. You generally do this at trailheads and destinations, but during a long day it should be done during travel as well. (Beware that all GPS units will show altitude, but many do NOT have a barometric altimeter and may be somewhat inaccurate due to the nature of how the GPS system renders altitude.)

2. At home, prepare your map by inking in route lines and designating major milestones such as stream crossings and trail forks. If you have a GPS and map software package, use it to get GPS coordinates and exact elevations for these points, and write them on the map. At the same time, for GPS practice get your routes marked in your GPS unit.

3. If your day requires more than a lunchtime map check, keep your map accessible by folding to show your route, and stowing in a flat ziploc bag. When reading frequently, carry by doubling over and sticking it in the thigh pocket of your alpine pants, or behind the zipper of your jacket. Keep your compass and altimeter equally handy.

4. As the day progresses, you want to have that map out often and ALWAYS know where you are on it. You do this by orienting the map up with your compass as described above, then visualizing the terrain. With good visibility, mountain landscapes provide plenty of landmarks that make this easy. In a storm you may find yourself counting things like stream crossings and using estimated travel speed along with altimeter readings to plot your position. Much of this, and that’s where the GPS comes into its own.

5. The key to effective map work in the field is frequent use. Along with that, keep your whole group involved in the map reading — having other sets of eyes on the process will prevent your mind from playing tricks on you.


The list:
10. Jump start a car without blinding yourself.

9. First-aid a serious laceration.

8. Rip skins in the wind without giving your scalp a bikini wax.

7. Fix a broken ski pole with duct tape and pocket knife.

6. Do a jump turn in the face of danger.

5. Start a fire in the snow — while you’re shivering.

4. Read a topo map quickly.

3. Quickly dig a person out of an avalanche.

2. Keep your feet warm.

1. Practice a humble mindset so caution rules the day.



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Comments

4 Responses to “10 Things to Know — Part 7: Read That Topo”

  1. Eyesack September 28th, 2007 10:44 am

    This is a cool program that I saw on another blog. It’s great for conceptualizing topo maps

    http://www.themountainculture.com/2007/09/21/world-wind-another-trip-planning-tool/

  2. barry September 29th, 2007 3:05 pm

    Number 4 is one that I see beginners struggle with. Always orient the map to the way you are looking, it makes the world make sense almost immediately.
    Also learn to pin point your position from the GPS location using the UTM grid.
    Consider getting a map romer.

  3. Terry October 1st, 2007 2:10 am

    FWIW, I dreamed up this map tool ( http://www.slidewright.com/Misc/MapTool.pdf) that is useful on 7.5′ maps (UTM or Lat/Long) and has some useful tidbits included, along with GPS point finding. Also, if you get some waterproof map paper and print this, or anything, with an inkjet printer, you’d be amazed how durable and lightweight the stuff is.

  4. roberto September 27th, 2008 1:46 am

    Thanks for the map info, good stuff.

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