Navigating the Wilderness Using Topographical Maps

Those of us who are constantly looking for a better place to set up a portable station would do well to learn how to read topographical maps. What makes topographical maps so different from a common road map are contour lines. Contour lines are lines drawn on a map at a constant elevation. That is, if you follow a line labeled "6500," everywhere it goes on your map will be at 6,500 feet above sea level. If you could walk along that line, no matter how far you went you would neither gain nor lose altitude. The empty space between contour lines is called the contour interval. It always stays the same on a given map although it can vary from map to map depending upon the scale. Finally, every fifth contour line is called an index contour. Index contour lines are darker and in many cases its elevation is printed several places along its course.

Figure 1 shows a portion of a topographical map from the central California Sierra mountains. The top of the map is oriented toward the north. The contour interval (distance between contour lines) is 40 feet. That is, adjacent lines are either 40 feet higher or 40 feet lower than their neighbor.

Study the map and locate the index contour marked 4800. As was stated earlier, at anywhere along this line the elevation will be a constant 4,800 feet above sea level. In the center of the map is a peak with a marked elevation of 5104 feet. Notice that the contour lines to the west of the peak are spaced quite close together. What the map is telling you is that the approach from the west is very steep because the contour lines are very closely spaced. A photograph confirms what the map says.

Take another look at Figure 1 and note the contour lines to the northeast are much more widely spaced. This can only mean that the terrain is not nearly so steep as the western approach. Another photograph shows the difference. Whereas the westerly approach is a hard climb, coming in from the other side is almost a leisurely stroll.

One more quick glance at the map shows that the top of the hill is pretty much flat and quite small. The fact that it is colored green indicates it is tree covered. White would mean it was covered with almost anything but trees or water. That is, it could be barren, grassy, covered with rocks or sand, boulders or just plain dirt. Another photograph shows it to contain a mixture of trees and boulders.

The view from the top of the hill is breathtaking but it is still not an ideal antenna location for a west coast QRPer trying to work the eastern seaboard. Russ Carpenter taught us that a very steep slope (or better yet, a cliff) facing east is what we need. Scan a topographical map for closely spaced contour lines on the easterly slope of a high hill or mountain. Also look for a broad valley (widely space contour lines) at the base of the mountain. Set up your dipole on the edge of the cliff and prepare to fill your Flight of the Bumblebee log up is very short order. That's what AA7QU does.