Arctic Circle
Tropic of Cancer
Equator
Tropic of Capricorn
N
5 000 km
0
1:212 500 000
120º W
140º W
160º W
180º
160º E
140º E
60º S
40º S
20º S
20º N
40º N
60º N
1
16
3. GEOGRAPHIC COORDINATES
The geographic coordinates system is network of imaginary horizontal and vertical
lines that are drawn on globes or maps. These lines are called
parallels
(lines of
latitude) and
meridians
(lines of longitude).
Parallels and meridians form an imaginary geographical network, in the form of a grid
4
,
which allows us to locate the exact position of any place in the world.
3.1. Parallels
The
Equator
is an imaginary
circle around the widest part of
the Earth. It is 40075 km long.
It divides our planet into two
equal halves or
hemispheres
,
a Greek word meaning half
a sphere. The top half is the
Northern Hemisphere
and the
bottom half is the
Southern
Hemisphere
.
Parallels
are imaginary lines
that circle the Earth parallel
to the
Equator
.
The Equator is 0° latitude. After that, there are 90 parallels to the north and another
90 to the south.
Some of these parallels are very important. In the Northern Hemisphere, there is the
Tropic of Cancer
and the
Arctic Circle
.
The area between the Equator and the tropics (the Intertropical Convergence Zone)
has
low latitudes
; the area between the tropics and the polar circles are
medium
latitudes
and the area between the polar circles and the Poles has
high latitudes
.
3.2. Meridians
The
prime meridian
or
Greenwich meridian
is 0°
longitude. It is named after the
British observatory at Greenwich
because the prime meridian runs
through the observatory. This
is the point of reference for all
other meridians.
There are 180 main meridians to
the east and another 180 to the
west.
Meridians are imaginary
semi-circles that go from pole
to pole.
latitud
norte
latitud
sur
longitud
oeste
longitud
este
T
r
o
p
i
c
o
f
C
a
n
c
e
r
E
q
u
a
t
o
r
(
0
°
)
T
r
o
p
i
c
o
f
C
a
p
r
i
c
o
r
n
A
r
c
t
i
c
C
i
r
c
l
e
A
n
t
a
r
c
t
i
c
C
i
r
c
l
e
latit e
north
latitude
so th
longitud
west
longitud
east
G
r
e
e
n
w
i
c
h
m
e
r
i
d
i
a
n
(
0
º
)
4
grid:
pattern of straight lines that form
squares
5
intersect:
to meet or cross
6
range:
to vary or extend between limits
