1 of 9

Write now Article Tools

Page 2 of 2

that tells you the contour interval, the altitude change between contour lines.

With practice you can imagine the shape of hills, ravines, and ridges by looking at the contour lines on the map. Note that the only way to see which way the slope runs is to find the index lines. That means that the contours for a ridge may look identical to those of a ravine. The only way to distinguish is to look at the index lines. Contour curves on a ridge will point downhill, those for a ravine will point uphill. Sadly I cannot draw example contours here (though there are examples in my book). Practice in an area you know until you can easily relate the map to the actual terrain.

Progress to areas you don't know well, then to new areas. By moving up the knowledge and skill ladder slowly you can avoid getting lost while learning how not to get lost.

Learn about declination, the difference between true and magnetic north. The compass points to the magnetic north pole, not true north. However maps generally use true north (actually grid north but the difference is smaller than you can measure with your compass). You need to know how to go back and forth between the two, another topic beyond the scope of this brief article. Several books, including my own, describe that skill.

Good maps will have a declination indicator in the margin but don't trust that if the map is more than a couple of years old. The magnetic north pole has started moving fairly fast of late. The USGS has a web site that will allow you to get the latest declination for anywhere on earth. Go to

http://geomag.usgs.gov/model s/models

To use the site you will need latitude and longitude of the area of interest. You will have to tell it which model to use. As I write this, the site suggests use of the igrf-2000 model. I believe that is outdated since it will not calculate values for times after the year 2004. There is an igrf-2005 model available on the site. That one will calculate declination for 2007 or later.

Be careful when you enter the location of interest into the calculation form. Be certain to use the correct north or south value for latitude and east or west for longitude.

This calculation will give you a lot of information, but you are probably most interested in the declination line, about the third line down and labeled "D" on the output.

In summary, study map and compass skills and practice them carefully. Learn to relate what you see on the map to the real terrain and to use the compass correctly. Those skills will go a long way toward keeping you out of trouble in the backcountry.

Learn more about this author, Hal Lillywhite.
Click here to send this author comments or questions.

• << previous page
• 1
• 2

Add your voice

Know something about Basic map and compass skills?
We want to hear your view. Write now!