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lines in the map. For example, it may be constant along any given
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parallel. This would mean that features lying on the 20 parallel are
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equally distorted, features on the 40 parallel are equally distorted
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(but differently from those on the 20 parallel), and so on.
2. Area. If a map preserves area, then the size of a feature on a
map is the same relative to its size on the earth. For example, on an
equal-area world map, Norway takes up the same percentage of map

space that actual Norway takes up on the earth. To look at it another
way, a coin moved to different spots on the map represents the same
amount of actual ground no matter where you put it. In an equal-area
map, the shapes of most features are distorted. No map can preserve

both shape and area for the whole world, although some come close
over sizeable regions.
3. Distance. If a line from a to b on a map is the same distance

(accounting for scale) that it is on the earth, then the map line has true
scale. No map has true scale everywhere, but most maps have at least
one or two lines of true scale. An equidistant map is one that

preserves true scale for all straight lines passing through a single,
specified point. For example, in an equidistant map centered on
Redlands, California, a linear measurement from Redlands to any

other point on the map would be correct.
4. Direction or azimuth (figure 6.3.), is measured in degrees of
angle from north. On the earth, this means that the direction from a to
b is the angle between the meridian on which a lies and the great

circle arc connecting a to b.

Figure 6.3. The azimuth of a to b is 22 degrees.

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