fraction; in other words, 1/100,000 is a smaller number
than 1/50,000.
c. STANAG 3677 lists the following as standard
scales for military maps:
1: 1,000,000
1: 500,000
1: 250,000
1: 100,000
1: 50,000
1: 25,000
3-5 Mercator Projection
a. The Mercator Projection is a cylindrical projection
in which the rotational axis of the ellipsoid coincides
with the axis of the cylinder so that the equator is
tangent to the cylinder. See Figure 3-2. Points on the
surface of the ellipsoid are projected onto the cylinder
from the origin located on the equatorial plane and
varies around three-quarters of the way back from the
projected area. The cylinder is then opened and
flattened to produce a plane surface. See Figure 3-3.
The parallels of latitude and meridians of longitude
both appear as sets of parallel lines that intersect at
right angles. The meridians are equally spaced, but the
distance between parallels increases as their distance
from the equator increases. The poles cannot be shown
on this projection. The normal limits are from 80° N
latitude to 80° S latitude.
b. As the distance from the equator increases, so does
the amount of distortion, for example, the map scale at
60° N or S latitudes is nearly twice the map scale at the
equator. Maps or charts with this projection will
distort the size of an area; this is why Alaska appears
to be the same size as the lower 48 states. This
projection is not commonly used for military purposes
except in some cases where the entire earth must be
displayed and relative positions of land masses are
more important than size and distance.
Figure 3-2 Mercator Projection
DRAFT
3-3
Figure 3-3 Mercator Projection Flattened onto a Plane
EQUATOR
(TANGENT
POINT)
80°
75°
60°
45°
30°
15°
0°
15°
30°
45°
60°
75°80°
80°
75°
60°
45°
30°
15°
0°
15°
30°
45°
60°
75°
80°
90°
75°
60°
45°
30°
15°
0°
15°
30°
45°
60°
75°
90°
180°
165°
150°
135°
120°
105°
105°
120°
135°
150°
165°
180°
