Translations:Adventist Youth Honors Answer Book/Recreation/Orienteering (General Conference)/9/en

4. Know the meaning of the following terms:

a. Elevation

The height of a point relative to sea level.

b. Contour interval

The elevation change between adjacent contour lines on a topographic map. If you travel from one contour line to another, your change in elevation will equal the contour interval.

c. Magnetic North

Magnetic North is the direction a compass will point, which is towards the North Magnetic Pole. The North Magnetic Pole is not the same place as the Geographic North Pole. The North Magnetic Pole is the point on the Earth's surface where the Earth's magnetic field points directly downwards. This pole is constantly wandering; its estimated 2005 position was 82.7° N 114.4° W.

d. Declination

The angular difference between magnetic north and true north (defined in reference to the Geographic North Pole), at any particular location on the Earth's surface, is called the magnetic declination. In other words, it's how far off a compass is from True North, or the correction that must be applied to a compass reading.

e. Scale

An important property of a map is the scale. It can be indicated by a scale bar and/or a ratio 1:n. This enables the map user to measure a distance on the map and determine the distance on the ground. These days maps are usually produced under the metric system which makes it easy to perform this task. Maps are usually produced at standard scale factors of (say) 1:10,000 or 1:50,000 or 1:100,000 and all you need to do is take a measurement on the map (in mm) and multiply that figure by the scale factor to determine the distance on the ground. However, maps from some countries may use imperial units, especially older maps. These maps displayed scale ratios but often they were of the form 60 chains (a chain is 22 yards, or 66 feet) to 1 inch or 2 miles to 1 inch, etc.

f. Measuring

The act of determining distance on a map and translating it to distance on the ground. In order to do this translation, you must know the map's scale (see above). Measuring can be done with a ruler or with calipers.

g. Back-azimuth

See under azimuth below.

h. True North

True North is the direction from any point on the Earth's surface to the Geographic North Pole.

i. Azimuth

The azimuth is a compass bearing expressed in degrees. There are 360° in a circle, and North is, by convention, 0° (or 360°). East is 90°, South is 180°, and West is 270°. While azimuth expresses the compass bearing in the direction of interest, the Back Azimuth expresses the compass bearing in exactly the opposite direction. In other words, azimuth is the direction to which you are going, and back azimuth is the direction from which you are coming. The back azimuth can be calculated by adding or subtracting 180° from the azimuth. Add if the azimuth is less than 180°, otherwise subtract.

j. Distance

Distance is the measure of length, or how far apart two points are away from each other.

k. Ground forms

The surface of the earth; the outer crust of the globe, or some indefinite portion of it.