To learn more about latitude, longitude and other geographic
concepts, pick up our Discovering Maps book. To buy this item
online click here or browse our complete
catalog.
| To find a place exactly, you need crossing lines that
create an intersection. This is a grid system. One grid
system is used by mapmakers all over the world. It helps
you locate any place on Earth. It is known as the latitude
and longitude grid |
Halfway between the North Pole and the South Pole
is an imaginary line, the equator.
The equator goes around the middle of Earth like a belt.
It divides our planet into the Northern Hemisphere and
the Southern Hemisphere.
The equator is a line of latitude. The other lines of
latitude are north and south of the equator. They are
parallel to the equator. Parallel lines run in the same
direction and are an equal distance apart at all points.
They never meet. Thus, lines of latitude are also called
parallels. They run east-west around the globe. |
Parallels measure distance north or south
of the equator. This distance is measured in degrees.
Earth, as a circle, is divided into 360 degrees (360o).
We measure latitude starting at the equator. Its address
is zero degrees latitude, or 0o latitude.
The distance from the equator to the North Pole is 1/4
of the distance around the Earth. So the North Pole
is at 90 degrees north latitude. The distance from the
equator to the South Pole is also 1/4 of the distance
around the Earth. What is the latitude of the South
Pole? |
|
You can measure your latitude by using the night
sky. In the Northern Hemisphere, find the North
Star, Polaris. Extend one arm toward the star.
Extend your other are toward the horizon. The
horizon is the point where the
sky and land seem to meet in the distance.
Use a protractor to measure the number of degrees
between your outstretched arms. If the angle is
40 degrees, you are locate 40o north.
At the equator, Polaris appears right at the horizon.
You are at 0o latitude.
What latitude do you find if you try this? How
close is this to an accurate figure found in an
atlas? |
|
Another set of imaginary lines helps
us measure distance east and west. These are lines of
longitude. Each line of longitude runs
from the North Pole to the South Pole. These lines are
also called meridians.
Each meridian travels halfway around the Earth. Along
its imaginary journey it crosses each line of latitude
once. These intersections mark an exact location for
any point on Earth.
Longitude lines are measured in degrees, just as latitude.
However, there is no natural starting or stopping point
for east and west. So mapmakers need a place to begin.
They call that line of longitude the prime meridian.
Its address is zero degrees longitude, or 0o
longitude.
From the prime meridian, you can travel west halfway
around the Earth to the 180o east longitude
line. At the 180o line, east meets west:
180o E and 180o W are the same
line! |
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Look at the globe to the left. Notice that the lines of longitude do not stay
the same distance from each other. Meridians are the
farthest apart at the equator. They are closer together
at the poles.
In fact, one degree east-west is 69 miles at the equator.
At the poles there is no distance between each degree
line. They all meet at the same spot! |
| Learn about some of the projections used in
mapmaking today. Take a look at our Projection
Animations page. |
Hammond
Projection Applet
An interactive demonstration showing how projections can vary
the representation of the Earth when stretched
onto a flat surface.
You can view it in a separate window or as a regular web page.
Please select from
the right two choices.
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To learn more about latitude, longitude and other
geographic concepts, pick up our Discovering Maps
book. To buy this item online
click here or browse our complete catalog.
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