How did ancient sailors find their way
across the world’s great oceans?
They began to lay out the earth in a grid
system, known as latitude and longitude.
On a map or globe, lines of latitude run east and west,
which means to measure from one to another, you
would go north or south. Thus latitude is always
measured with a direction of north or south.
The earth is divided into two latitudinal hemispheres,
northern and southern. The dividing line of latitude is called
the equator and it is measured as 0˚. All lines of latitude
above it are in the northern hemisphere and have a
directional latitude of north. Those below the equator have
a directional latitude of south.
Lines of longitude run north and south, thus measuring east
and west. The “starting point” line of longitude is known as
the Prime Meridian (0˚) and all lines of longitude east of it
have a longitudinal direction of east. All lines west of it have
a longitudinal direction of west.
Longitudinal lines all meet at the poles on a globe, but on a
map that proves to be very difficult. That is why there are so
many types of world maps.
In any kind of world map,
some land masses will be
distorted, either near the
poles or near the equator.
Since the Prime Meridian (0˚ longitude) could have been any
line running north and south, do you know why that
particular line was chosen?
It runs through Greenwich, England (just outside London),
in order to honor the Royal Geographical Society of England,
because of its contributions to sailing, map making, and astronomy.
In which two hemispheres does Georgetown, Texas lie?
One degree of latitude or longitude is
approximately 73 miles.