1 of 17

Write now Article Tools

Page 2 of 6

across the top or bottom margin for your longitude. The intersection of these lines is the point that you are trying to find. Occasionally, a map guide will give the location of a point of interest in one system, but your map is the other. There are websites that will convert the values for you, and you can also learn how to convert points between the two lat-long systems.

Contour Interval - Many map legends show the contour interval, which is the height between two contour lines drawn on the page. If the legend doesn't show the interval, you can calculate it from the map. Typically there are thicker "index" lines at a larger interval that have the elevation printed on them. For example, the contour interval might be 20 feet, but every fifth contour line would be an index contour. To calculate your contour interval form the map, choose an index line, and then find the index line with the next highest value, subtract the first number from the second number, for the total height between the two. Then, count the total number of contour lines between the two index lines, and add 1. Divide the total height by this number, and you have determined your contour interval. For example: your first index line is a 1400 ft, the second is at 1500 ft, and there are 4 contours between the two index lines; so you would end up dividing 100 by 5, and have a 20 ft contour interval, which is standard on USGS maps.

Symbology - most topographic maps show more than just topography. Roads, trails, buildings, rivers, and other physical features might be shown. Also, ground cover symbols or colors are present on many maps, showing where forested lands or agricultural fields are located. An important symbol to recognize is the "x" used for "benchmarks," which are metal markers placed in the ground by the United States Geologic Survey or the National Geodetic Survey. These benchmarks are carefully measured so that they are fairly accurately represented on a map, and can make way-finding easier.

Magnetic Declination - We've all heard that magnetic north doesn't quite line up with true north, and the difference between the two differs slightly depending on where you are on Earth. Topographic maps typically show this difference in the lower left corner. If having to add or subtract constantly to find your true bearing sounds like too much work, you can find many compasses that have "adjustable declination" which allows you to set the declination on the compass and then just travel as you normally

• << previous page
• 1
• 2
• 3
• 4
• 5
• 6
• next page >>

Add your voice

Know something about Preparing for a hike using a topographical map?
We want to hear your view. Write now!