1. Focus: Latitude and Longitude: The Earth’s Coordinate System
Earth Science: Measuring Earth

2. Learning Objective By the end of today ’s class students should be
able to determine and
measure latitude and
longitude.

3. Latitude Distance in degrees north or south of the equator (0°)
If you Draw a line from any point on the Earth ’s surface to the center of the Earth, the angle that line
makes with the equator will be that location ’s latitude.

4. Parallels of Latitude 90°N 30°N Parallels of 15°N latitude 15°S 30°S

5. lATITUDE Quick Review of Latitude and Longitude
Measured in degrees North and South of the Equator. Lines drawn parallel to each other running west to
east.

6. Longitude
Distance in degrees, measured east or west, of the Prime Meridian (0°).
Meridians are imaginary semicircles that converge at the poles.
The maximum longitude is 180°

7. Meridians of
Longitude °W °E

8. LONGITUDE Quick Review of Latitude and Longitude
Measured in degrees East or West of the Prime meridian.
Lines drawn running North and South

9. Writing latitude and longitude
From USGS Maps :
The latitude of White Plains, New York is about 41.06°N or Just… 41.1° N
The longitude of White Plains, New York is about 73.76°W or Just 73.8°W
The coordinates of WPNY are written
41.1°N Lat, 73.8°W Long
Latitude is always (usually) written first
Longitude is always written(usually) second

10. Writing latitude and longitude
Latitude is always (usually) written first
Longitude is always
written(usually) second
EX ° S 78.9° W

11. Complete the following in your notebook:
Latitude = 5°N, Longitude = 176°W
5°N Lat, 176°W Long
Latitude = 81°S, Longitude = 2°E 81°S lat, 2°E Long

12. Where in the World
5°N, 176°W
41°N, 73°W
81°S, 2°E

13. Latitude above Equator using Polaris
The altitude of Polaris (height above your feet in the sky) equals the Latitude of where
you are at (only in the Northern hemisphere), North Star is Polaris.
The position of Polaris (angle of elevation) is fixed throughout the night
The altitude of Polaris is equal to the
observers latitude. OR you can say……
Angle of Elevation = Latitude on Map

14. Polaris/North Star Polaris is overhead at 90°N (The North Pole)
Polaris is at the horizon at The Equator

15. Measuring Latitude 41ºN What is the astronomers latitude??
= 41º
Zenith: Point in the sky directly above the observer

16. Measuring Longitude Have to know:
The solar (clock) time at the Prime Meridian (Greenwich, UK)
• Called Greenwich Mean Time (GMT)
Local Solar Time (clock) is the time at your location. Such time, called mean solar time
• Look at your watch or a clock

17. Celestial HEMISPHERE
Altitude of Polaris is ?
50º

18. Movie about Northern Sky
x.cfm?guidAssetId=E4323B12-6BF2-42E
BD97E1F29643&blnFromSearch=1&produ
ctcode=US
Also,
ces/skyobserve/constellations4.htm

19. Measuring Longitude Step 1: Calculate the time difference, in
hours, between local clock time and the
Greenwich time
Step 2: Multiply this time difference by 15°
Step 3: Determining Longitude: EL WE
EL - East Later
WE - West Earlier

20. Why Multiply by 15°?? The Sun moves across the sky (It’s
really the earth turning)at a rate of 15° per hour.
15° = 1 hour

21. Measuring Longitude example
Greenwich Time = 5:00 PM
Local Time = 12:00 PM
Time Difference =
5 hours
** Is local time earlier or later than
Greenwich Time, are you east or west of the
Prime Meridian?? EL WE
Multiply ˘
5 * 15° =
75°W

22. Movie bout Longitude http://www- c.pbs.org/wgbh/nova/longitude/find/
(www-c.pbs.org/wgbh/nova/longitude/find/)

23. Summary:
Latitude
Latitude is measured in degrees north or south of the equator.
To find the latitude of
a location you have to determine whether
that location is north
or south of the
Equator!

24. Summary: Longitude Longitude is measured in degrees east or
west of the Prime Meridian.
To find the longitude
of a location you
have to determine
whether that location is east or west of the
Prime Meridian!

25. Measuring Latitude Using Polaris
Latitude = Altitude of Polaris
Polaris (The North Star) is only visible in
the?
Northern Hemisphere
Ex. The altitude of Polaris is 78°. What is
your latitude?
78°N