Don't Be Intimidated by Map and Compass Language

Map and compass language can leave a novice wondering what it all means. But
navigational terms, such as magnetic declination diagram, hydrographic and
hypsographic features, and orienting lines sound more intimidating than they are.
As with learning any new language, you start with the basics and work forward. Navigation requires understanding the essential parts of the compass and also locating the markings on a map. As with any other skill, the more you practice, the easier it becomes and it will seem like second nature.

Understanding Your Compass

All orienteering compasses have a red needle in the compass housing, called a
magnetic needle because it is attracted by the magnetism of the earth and always
points to magnetic north.

Magnetic north is located in upper Hudson Bay, about 800 miles south of geographic or "true north." True north is the region at the top of the world known as the north pole. In essence, maps and compasses operate under two different navigational systems, the two norths. The difference between the two is called declination or variation.

The graduated 360-degree compass dial makes up the rim of the compass housing
mounted on the baseplate. The dial is usually marked with cardinal points: N, S, E
and W. The orienting arrow on the base is used as a reference to align the magnetic
needle for a heading.

The baseplate includes a direction of travel arrow, which points in your direction of
travel when the compass is oriented, and an index line, the point on the compass dial in which you set your heading. Upgraded compasses may include a magnifying glass, an inch rule and one or more map scales.

Understanding Your Map

A commonly preferred topo map is the 7.5 minute series, which means the map covers 6-1/2 x 8-1/2 miles of latitude and longitude. Most topo maps available today are drawn to a 1:24,000 scale -- one inch on the map equals 24,000 inches or 2,000 feet on the ground.

The map will have a contour interval number that measures the distance in height
between two adjacent contour lines on a map. When contour lines run close together, the grade is steeper; when spaced far apart, the terrain is fairly flat. Every fifth contour, the contour index line, gives the elevation in feet above sea level.

Color-coded symbols on the map help you read it easier. Blue designates hydrographic features such as lakes, rivers and streams. Green refers to hypsographic features -- vegetation, forests and scrub. Brown represents elevation lines and landforms, and black indicates buildings, railroads, roads and other man-made structures. Clearings such as fields are shown in white.

When using a map and compass together, you have to adjust for declination because the map indicates true north and the compass indicates magnetic north. The magnetic declination diagram at the bottom of the topo map shows the distance between the two norths. There is a way to avoid confusion; The easiest way to adjust the magnetic north lines of the compass to the true north
lines on the map, is to draw magnetic lines on the map. Using a ruler,
draw a line up from the declination diagram's magnetic arrow. Then draw parallel
lines across the map, spaced one to two inches apart. These magnetic-north lines will correspond precisely to the compass needle, allowing you to correct for declination.

Some compasses, like Silva's Ranger and Landmark types, have adjustable
mechanisms to correct for declination. If you buy a compass without a declination scale, you can still use it with a map by following the magnetic declination diagram.

Learning to use a map and compass is fun and can give you a sense of
accomplishment. Once the language starts to sound familiar, it's easy. You can find more orienteering information on the Silva Web site- www.silvacompass.com.