II
How are locations named on earth?
A) Coordinate system is used
1. includes 2 numbers
2. system used must provide a unique name for
every different location
3. system used for each, must also apply
to a sphere
4. system used on round earth is latitude
and longitude.
B) Latitude
1. imaginary lines are called parallels
2. "drawn" East to West
3. equal distant apart
4. unit = degree and direction
1 o is about 69 miles or 111 km
5. equator = frame of reference
0 degrees latitude
divides the earth into Northern
and Southern hemispheres
6. latitude is the measurement of angular
distance North or South of the equator
7. range = 00 to 900 North or South of the
equator
8. latitude is the same along any parallel E or W
It will change only if you move North or South
C) Longitude
1. imaginary lines called meridians
2. "drawn" N to S, and meet at the poles
3. not equal distant apart, closest at the poles,
furthest at the equator
4. 10equals approximately 69 miles or 111 km
only at the equator
5. Prime Meridian = frame of reference, 00
longitude. Drawn through Greenwich,
England. Divides the earth into East and
West hemispheres.
6. Longitude measures angular distance E or W
of the Prime Meridian.
7. range is 00 to 1800East or West
8. longitude does not change if you move
N or S, only when you move E or W
see page 57
D) How was latitude determined?
1. latitude is based on celestial observations of
the pole star
---- North latitudes use Polaris also known as the
North Star The South latitudes use Sigmus
Octanus
2. A sextant measures a stars altitude above the
horizon
3. altitude of the pole star = your latitude
4. if you move North, the altitude of Polaris
increases, so latitude increases
5. if you move East or West, the altitude of the
pole star (Polaris) remains the same and so
does the latitude
E) How was longitude determined?
1. longitude is based on celestial observations of
the sun
2. the sun indicates the time of day. Solar noon
occurs when the sun is on the observers
celestial meridian
3. chronometer is a clock which indicates GMT
(Greenwich Mean Time)
4. longitude = 15 degrees times the difference
between you and GMT
---if you are ahead of GMT you are East
---if you are behind GMT you are West
5. the 24 time zones are 15 degrees apart