120 THe geOgRaPHiC anD
CaRTOgRaPHiC FRaMeWORK
nation reveals that this is not possible. Large numbers of mathematical projections
have been developed, especially in recent years, and many are designed for a specific
purpose. Many, although by no means all, are equal area. Only four of these will be
discussed here for purposes of illustration.
sinusoidal Projection
The
sinusoidal projection, which is also called the Sanson–Flamsteed projection,
appears to have been first used by Nicholas Sanson about 1650. This is an equal-area
projection that has a straight central meridian and straight, equally spaced, true-to-
scale parallels. The central meridian is also true to scale. This makes it possible to
measure distance along any parallel (not great circle distances) and along the central
meridian. A zone of least distortion is produced along the equator and central merid-
ian (Figure 6.34). Any meridian may be chosen as the central meridian. The projec-
tion gets its name from the meridians being trigonometric sine curves. Shapes toward
the outer margins of the projection in the high latitudes are badly distorted, but for
areas in the center of the projection, such as Africa or South America, the sinusoidal
projection would be a good choice.
Mollweide Projection
In some ways, the Mollweide or homolographic projection (Figure 6.35) resembles the
sinusoidal. Both are equal area and show the entire earth, and both have a straight
central meridian and straight parallels. The Mollweide, however, is an ellipse lacking
the pointed poles of the sinusoidal. Only the 40th parallels north and south are cor-
rect in length, and the parallels are not spaced truly on the central meridian. Shapes
are not as badly distorted in the polar areas as they are on the sinusoidal. On this
fIgURe 6.33.
The polyconic is formed of a series of standard parallels. It doesn’t show the
entire earth well and is usually
used only for small areas, such as topographic maps.
The earth’s graticule and Projections 121
projection, the zones of best representation are around the central meridan and the
40th parallels.
goode’s Homolosine Projection
In 1923, J. Paul Goode devised the homolosine projection by combining the sinu-
soidal and homolographic projections. The homolosine is made up of the sinusoidal
from 40°N to 40°S and the homolographic from the 40th
parallels to the poles,
thus combining the “best” parts of the two projections and extending the zone of
