The earth’s graticule and Projections 103
point. That is, if there is stretching in the longitudinal dimension, it must be matched
with an equal amount of stretching in the latitudinal dimension (Figure 6.12). As
a result, angles are preserved at the expense of a severely distorted
areal scale, and
squares of 100 square miles in different parts of the globe, while remaining square,
will have different apparent sizes on a conformal projection. Figure 6.13
shows a
conformal world map compared to an equal-area map. Note the size of Greenland on
these two maps. Compare the shape and size to that found on a globe.
Because of the conflicting requirements of equal-area and conformal projections,
it is not possible to preserve both properties on a flat map;
it is impossible to design
an equal-area conformal projection. These properties
can be achieved simultane-
ously only on a globe.
eQUiDisTanT PROJeCTiOns
A map is called equidistant if distances are shown correctly. Equidistance is not
attainable over the entire map; the distance scale of a map is correct only along cer-
tain lines or from specific points.
aziMUTHaL PROJeCTiOns
Projections that show azimuths correctly are called
azimuthal or
zenithal projections.
Unlike conformality and equivalence, this property cannot exist everywhere on the
map.
Azimuth is correct only from a single point, the center; it is not possible to mea-
sure the azimuth between any other points on the map. A map that shows constant
compass
direction is not an azimuthal map.
COMPROMise PROJeCTiOns
These are also called
minimum error projections, a somewhat misleading term. These
projections have no particular property except appearance. These are not conformal,
but shapes may not be terribly distorted; they are not equal area, but areas may not be
