Latitude, Longitude and Time Zones
1. THE BASICS
The coordinate system for the Earth is Latitude and Longitude.
Latitude: angular distance, measured in degrees, from the Equator.
Longitude: angular distance, measured in degrees, from the Prime meridian
Latitude Lines
Latitude lines: run east/west but measure north/south.
Called parallels
Form complete circles.
Longitude lines: run from the N. Pole to the S. Pole
Not parallel  the longitude lines meet at the poles
Called meridians
Each meridian or longitude line is a half-circle.
180º longitude is called the International Date Line.
By combining Latitude and Longitude
exact locations can be determined:
Point A is 60ºN of the Equator and
90ºE of the Prime meridian (60N,90E)
Point B is at 30ºN latitude and 90ºW longitude
Point C is at 60ºN latitude and 60ºW longitude
Point X is at 60ºN latitude and 150ºW longitude
Longitude lines
2. TIME ZONES
A. Time is based on your position relative to the sun.
B. Longitude determines time. Not latitude.
C. We have time zones because the Earth rotates.
D. The rotation is from the West to the East.
E. The rate of the rotation is 15º/hour.
F. Each time zone is approximately 15º of longitude wide. Political boundaries
make the distinctions rather than the longitude lines themselves.
G. Traveling east you need to set your watch forward
H. Traveling west you need to set your watch backward
I. East increased, West less
EX: If at point C, 60ºW longitude, it is 12PM
(noon) than at point B, 90ºW it is 10AM and at
point D it is 4PM.
Reason C and B are 30º apart. Therefore 2 hours
difference (15º/hr). And, since B is west of C,
the local time is earlier (west less).
Point D is 60º East of C. Hence, 4 hours
(60÷15=4) forward in time.
3. MORE DETAIL, MORE PRECISE
One degree of latitude or longitude is nearly 110 kilometers long. We often need to get
more precise than that. Degrees of latitude and longitude are broken up into miniscule
pieces – just as a foot is broken up into 12 inches – One degree on the Earth’s surface is
broken up into 60 minutes. Minutes can then be broken up into even smaller divisions
called seconds. There are 60 seconds in 1 minute of a degree.
Point C is between 5º and 6ºN latitude. It is half way between
them. The latitude of point C is 5º30’N (5 degrees, 30
minutes N latitude)
Point C is also between 71º and 72ºW longitude. It is much
closer to 72ºW than it is to 71ºW. The longitude of point C is
71º50’W (71 degrees, 50 minutes W longitude)
B: 5º45’N, 71º20’W
A: 5º45’N, 71º50’W
E: 5º07’N, 71º50’W
D: 5º30’N, 71º20’W
YOU MUST BE ABLE TO DETERMING THE PRECISE LATITUD AND
LONGITUDE OF NY CITIES FROM P.3 OF THE ESRT’s.