Locating Positions on Earth
Locating Positions on Earth
Coordinate Systems
Earth scientists use the latitude-longitude
coordinate system to identify locations on Earth’s
surface. Latitudes and longitudes are measured in degrees (°) and minutes (‘). Each degree (°) is made up
of 60 minutes (‘).Sydney,
Australia = 34°0’S, 151°0’E
Latitude
The equator (0°) marks the middle of the Earth –halfway between the North and South poles.
Latitude
The latitude of any point on the Earth
is the angular measurement between the
location and the equator using the center of the Earth
as a focal point.
Latitude measurements above the equator are referenced with an “N”
for Northern Hemisphere.
Latitude measurements below the equator are referenced with an “S”
for Southern Hemisphere.
Measuring Latitude
Scientists may use the position of stars in the night sky to determine the latitude of their position on the Earth’s surface.
Polaris (The North Star) is seen by observers in the Northern Hemisphere. The star is positioned in the night sky
nearly directly over the North Pole.
Measuring Latitude
Pointer stars in the “Big Dipper” constellation allow the viewer to find Polaris .
A sextant is an instrument used by an observer to determine the angle
between Polaris and the horizon.
observer
Polaris
horizon
Longitude
The prime meridian (0°) marks the middle of the Earth –halfway between the Eastern
and Western Hemispheres.
Longitude
The meridian that passes through
Greenwich, England has been designated as the prime meridian (0°).
The longitude of any location on the Earth’s surface is the number of degrees between the location and that of the
prime meridian.
Longitudes increase east and west from the prime
meridian to the International Date Line (180°)
Longitude measurements
east of the prime meridian are referenced with an “E” for
Eastern Hemisphere.
Longitude measurements
west of the prime meridian are referenced with a “W” for
Western Hemisphere.
Eastern Hemisphere
Western Hemisphere
Measuring Longitude
The longitude of a position on Earth’s surface can be determined if one studies the rate of Earth’s rotation
over time.
Measuring Longitude
Scientists will use GMT = Greenwich Mean Time as a means by which to gauge the
local time and location of longitude for an
observer.
For example, if the sun has reached its highest altitude in
the sky (local noon – 12 pm) at Greenwich, it will be 11am at 15°
E and 1pm 15°W.
0°12 pm
15°E1 pm
15°W11 am
Remember*** The Earth rotates from
west to east at a rate of 15° per hour.
Measuring Longitude – Sample Problem “If it 6 pm at Greenwich England, at
which location would it be 10 pm?”
B
CA
D