In survival situations you may be forced to make your way through unfamiliar terrain. By being prepared for a disaster, you may have had the foresight to secure some topographical maps of your area. The challenge for most people, though, is reading a topo map. These maps can help you get an idea of what the terrain is like between two specific points. These maps are very different from our common road maps and are filled with lines, symbols and jargon that can seem foreign. To start discerning these maps, you must first know the parts.
1. Contour Lines:
These lines connect points on the map that have the same relative elevation. Once you understand them, they can provide you an almost three-dimensional view of the landscape. Areas with tightly packed contour lines show very steep terrain while widely spaced lines show relatively flat terrain.
2. Contour Interval:
In the margins of the map there will be a notation for the contour interval. This tells you how far apart the lines may appear. This distance will be the same across the entire map. Depending on the detail of the map, intervals can range from 20 to 200 feet.
The map will include a distance graphic scale. It displays how a measurement on the map (1 inch, for example) equates to miles/kilometers of terrain shown on the map.
4. Index Contour Lines:
On topo maps, every fifth line is what is called an index contour line. They are bolder in color or density than other lines and provide an elevation reading for that area.
5. Map Reading Color & Shading:
Darker colors will show areas of dense vegetation while lighter colors show areas relatively sparse of vegetation. Areas with no color or shading represent open terrain.
6. Magnetic Declination:
This will be printed in the margin of the map and shows the difference between magnetic north (indicated by the “MN” symbol) and true north (or polar north, indicated by a star symbol).
7. Grid Guide:
The numbers displayed around the edge of a map represent two grid systems that can be used to determine your location.
8. Latitude & Longitude:
Exact latitude and longitude numbers are displayed in the corners of maps and at equal intervals between the corners.
9. Universal Transverse Mercator (UTM):
This system, used primarily by the military, divides the Earth’s surface into a number of zones.
When all of these parts are combined, they can enable you to determine your elevation, the ruggedness of the terrain around you and the most desirable route to travel to reach a destination. As with any survival skill, it is best to seek professional training to make sure you are completely prepared!
This article was originally published in SURVIVOR’S EDGE. Subscription is available in print and digital editions here.
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