Latitude and Longitude
Latitude
Latitude is the distance of a point on Earth
measured from north or south of the
equator.
The baseline for latitude is the equator. It
runs completely around the Earth at its
widest point, farthest from the poles. Every
place on the surface of the Earth is from 0 to
90 degrees north or south of this line.
Lines of Latitude cut through the earth to
the middle, creating angles.
All lines of latitude go
around the Earth
parallel to the equator.
Finding the actual
distance between the
lines of latitude involves
some large numbers.
The actual distance around the
Earth is 40, 000 kilometres. Since
the largest degree of latitude is
one-quarter of the globe, the
distance from the equator to
either of the poles is
approximately 10, 000
kilometres.
Because we know that the 90
degrees from the equator to the
poles is 10 000 kilometres, we
can easily calculate the distance
involved in one degree:
If 90 degrees equals 10 000 kilometres,
then one degree is 10 000 divided by 90.
This equals about 110 kilometres.
If 90° = 10 000 km
then 1° = 10 000/90 km
1° ≈ 110 km
Special Lines of Latitude
Because the Earth tilts on its axis, several
lines of latitude have special
characteristics.
These are the two Tropics and the Arctic and
Antarctic Circles
The Tropic of Cancer is 23½
degrees north of the equator,
and the Tropic of Capricorn at
23½ degrees south of the
equator.
The 23½ degrees reflect the
amount of tilt that the Earth
has on its axis relative to the
sun. This is why we have
different seasons at locations
away from the equator.
• On June 21, the sun is directly overhead at
the Tropic of Cancer; on December 21, the
sun is directly overhead at the Tropic of
Capricorn.
As the Earth goes around the sun, the sun
seems to migrate between the two tropics,
crossing the equator twice—on March 21 and
on September 21. In fact, the sun stays where
it is and the orientation of the Earth changes as
it revolves around the sun.
The tilt of the Earth has a strange effect on the
areas to the far north and the far south. North
of the Arctic Circle, located at 66½ degrees
north, the sun is above the horizon for a full
24-hour day during summer, and is below the
horizon for a full 24-hour day during winter.
The number of days of complete sunshine or
complete darkness varies, depending on
distance from the pole.
For example, 90°N undergoes six continuous
months of daylight and then six continuous
months of darkness, while 70°N undergoes only
about two months of each. Canada’s Far North
is sometimes called the “land of the midnight
sun.”
The location of the two “circles”—the Arctic
and Antarctic—is also determined by the tilt
of the Earth. We use the latitude of the North
or South Pole (90°N or 90°S) and subtract the
23½ degree tilt of the Earth.
That’s how we know where the circles are:
66½°N and 66½° S.
Longitude
The lines connecting the two poles
are known as lines of longitude, or
meridians. They run north and
south and always meet at the
poles. Because they meet at the
poles, the lines are not parallel.
The distance between any two lines
changes depending on the distance
from the pole. The lines are
farthest apart at the equator and
closest together at the poles.
The Prime Meridian is the basis
from which all lines of
longitude are measured; the
Prime Meridian is zero
degrees longitude.
The Prime Meridian does the
same thing for longitude that
the equator does for latitude.
It runs through the Royal
Observatory at Greenwich (in
London, England), and is
sometimes referred to as the
Greenwich Meridian.
Longitude is measured in
degrees. By definition,
longitude is the distance of
a point on the Earth’s
surface measured east or
west of the Prime Meridian.
Because the Earth is 360°
around, all meridians lie
between 0° and 180° east or
west of the Prime Meridian.
At 180° east or west of the
Prime Meridian is the
International Date Line,
which lies on the opposite
side of the Earth from the
Prime Meridian.
Specifying Locations Using Latitude
and Longitude
Can you find something if
you only know the
longitude?
Can you find something if
you only know the
latitude?
Why not?
With both latitude and longitude, you can find the exact
location of any specific point on the surface of the
Earth.
The numbers for latitude and longitude are always given
in the same order: latitude first and longitude second.
As a result, the first figure given for the location of a
place will have a north or south designation, and the
second will have an east or west designation. For
example, a mountain peak might be described as being
at 51°N, 97°W.
Each degree of longitude can also be divided
into minutes and seconds. For example, 49°
12' 30"E indicates that a location, perhaps a
fishing cabin, lies along a line of longitude 49
degrees, 12 minutes, and 30 seconds east of
the Prime Meridian. An exact location is
always quite lengthy, such as 35° 24' 12"S, 25°
23' 1"W.
N
N
Northern
hemisphere
N
Southern
hemisphere
S
S
S