The Geographic Grid
Monday, June 15, 2026 11:39 AM
The earth has no corners or edges, no beginning or end, but using 2 fixed points on earth
(the north & south poles) and the equator, we’re able to pinpoint our exact location (within
feet) on the 197 million square miles that make up the surface of the earth
- The system consists of east to west and north to south running lines on a map (or circles
on a globe)
- These circles intersect to create a grid
LATITUDE
- The east-west running lines are called parallels aka lines of latitude. The starting point
for the system of latitude is at the equator since it is the only circle that can be drawn
from east to west that divides the earth equally in half. This, by definition, is called a
“great circle.”
○ A great circle is any circle that can be drawn on earth, in any direction, that divides
the earth in half. The equator divides the earth into 2 halves, the northern
hemisphere and the southern hemisphere.
- Latitude lines are arranged parallel to one another, ranging from 0 degrees at the equator
to 90 degrees north and south at the poles. The equator is the 0 degree parallel, and any
degree north or south of this line is the angle which is created when you measure the
distance from the center of the earth, at the equator, to the surface, northward and
southward of the equator.
○ Since a 90 degree angle is created from the center of the earth at the equator to the
north or south poles, their measures are 90 degrees N and 90 degrees S,
respectively. Latitude lines are arranged east to west, but tell you how far north and
south you are from the equator.
LONGITUDE
- Longitude lines, or meridians, all converge at the north and south poles. All meridians
are great circles, since they all equally divide the earth in half. Because of this, up until
the late 19th century, there were many 0 degree meridians. This made it difficult to
coordinate trade & travel. At the International Meridian Conference 1884, a decision
was made to begin the 0 degree meridian, known as the "Prime Meridian" in
Greenwich, England. Part of that decision had to do with the position of the other half
of the Prime Meridian. This line, from north pole to south pole, half way around the
world from the Prime Meridian is called the International Date Line (IDL) at 180
degrees. While latitude lines are circles, longitude lines are half circles, numbered in
degrees east and west of the Prime Meridian 0 degrees, to the IDL at 180
degrees. Any point east of the Prime Meridian to the IDL is in the eastern hemisphere,
and any point west of the Prime Meridian to the IDL is in the western hemisphere.
Monday, June 15, 2026 11:39 AM
The earth has no corners or edges, no beginning or end, but using 2 fixed points on earth
(the north & south poles) and the equator, we’re able to pinpoint our exact location (within
feet) on the 197 million square miles that make up the surface of the earth
- The system consists of east to west and north to south running lines on a map (or circles
on a globe)
- These circles intersect to create a grid
LATITUDE
- The east-west running lines are called parallels aka lines of latitude. The starting point
for the system of latitude is at the equator since it is the only circle that can be drawn
from east to west that divides the earth equally in half. This, by definition, is called a
“great circle.”
○ A great circle is any circle that can be drawn on earth, in any direction, that divides
the earth in half. The equator divides the earth into 2 halves, the northern
hemisphere and the southern hemisphere.
- Latitude lines are arranged parallel to one another, ranging from 0 degrees at the equator
to 90 degrees north and south at the poles. The equator is the 0 degree parallel, and any
degree north or south of this line is the angle which is created when you measure the
distance from the center of the earth, at the equator, to the surface, northward and
southward of the equator.
○ Since a 90 degree angle is created from the center of the earth at the equator to the
north or south poles, their measures are 90 degrees N and 90 degrees S,
respectively. Latitude lines are arranged east to west, but tell you how far north and
south you are from the equator.
LONGITUDE
- Longitude lines, or meridians, all converge at the north and south poles. All meridians
are great circles, since they all equally divide the earth in half. Because of this, up until
the late 19th century, there were many 0 degree meridians. This made it difficult to
coordinate trade & travel. At the International Meridian Conference 1884, a decision
was made to begin the 0 degree meridian, known as the "Prime Meridian" in
Greenwich, England. Part of that decision had to do with the position of the other half
of the Prime Meridian. This line, from north pole to south pole, half way around the
world from the Prime Meridian is called the International Date Line (IDL) at 180
degrees. While latitude lines are circles, longitude lines are half circles, numbered in
degrees east and west of the Prime Meridian 0 degrees, to the IDL at 180
degrees. Any point east of the Prime Meridian to the IDL is in the eastern hemisphere,
and any point west of the Prime Meridian to the IDL is in the western hemisphere.
