In the Beginning

Where Are You?
  |  Gorp.com

First article in a seven-part series

A topographic map, by itself, isn't much good if you can't point to where you are on it. Similarly, a GPS unit isn't worth much unless you can read the coordinates of your location and then find that place on the map. That's happiness. Here's me . . . there's the river . . . there are these two hills . . . there's where I want to go. Get used to working from map to GPS and GPS to map—with a little compass work thrown in for good (safety) measure and you're a Backcountry Navigator.

It's not all that hard to learn.

Get out a topo map showing anywhere in North America.

Look down in the lower right-hand corner.

Find the notation for the number of degrees and minutes north of the equator where the map starts. Any other location on that map will be north of that starting point.

Now find the starting point, west of the prime meridian, also noted in degrees or degrees and minutes. Any other location on that map will be west of that starting point.

Follow the latitude marks up the right-hand side of the map usually noted in intervals of one minute. At any point, you can now state the number of degrees and minutes up the side of the map and quite accurately estimate parts or decimals of minutes.

Practice the same reading technique going left along the bottom longitude scale. Starting degree—count the minutes—estimate the fractions of minutes. Not difficult at all, is it?

Pick an easily identified point or object somewhere about the middle of the map.

Fold the bottom of the map upward until the edge of the paper is precisely across your selected point. Make sure that edge hits about the same place on the left and right latitude scales. With a pencil, mark the point where the edge crosses the right latitude scale. Write down the whole degree from where the map started in the corner—count the whole minutes up to just below your mark and write down that number—estimate the decimal fraction of a minute remaining and write that down, too. Put an "N" in front of the numbers.

Folding the right side of the map, align it through your point, square it, and mark the lower edge where it crosses the longitude scale. Count the whole degrees, minutes and decimal minutes of your mark from the corner and write it down with a "W" in front.

Congratulations!

You've just measured the location of a selected point on a topographic map and noted its coordinates. You could phone somebody and tell them exactly where your location is. You could enter those coordinates into a GPS unit and go there.


Published: 30 Apr 2002 | Last Updated: 15 Sep 2010
Details mentioned in this article were accurate at the time of publication

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