GEO 101, January 16, 2014, Latitude and Longitude
Finding your way …
How geographers locate where things are…
Best reference points are ends of rotational axis
Most common locational system
Latitude and Longitude
Measures angular distance in degrees, not distance in miles or km
Basic geometry: circle has 360 degrees
Babylonians ( ≈ 600 BC) chose the number 360. The reason is that their number system was based on 60. To compare, we base our number system on 10. For us, 10 is a nice, round number and we find it very convenient to count in multiples of 10. But the Babylonians liked 60.
LATITUDE
Midway between N & S pole is Equator = 0°
90° N
0°
90° S
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Latitude of Mobile ≈ 30° 42’ N.
Parallels of latitude measure the angular distance (degrees) north or south of the Equator.
Expressed in degrees, minutes, & seconds
60 minutes in 1 degree
60 seconds in 1 minute
The lines themselves run east - west like the rungs on a ladder
Latitude can be used to approximate distances based on following:
360° in a circle
≈ 25,000 miles around earth
25,000 miles / 360° ≈ 69 miles in 1°
One degree of latitude always ≈ 69 miles
This is true because parallels of latitude stay same distance apart
Find distance in miles between
Mobile and the Galapagos Islands, which is almost due south of Mobile
Mobile 30° 42’ N
Difference 30° 52’ or 30 + 52/60 degrees = 30.87°
30.87° x 69 mi/degree = 2130 miles
LONGITUDE
Arbitrary starting place at Greenwich (London), England
180° = International Date Line
East
West
N P
0° = Prime Meridian
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Meridians of longitude measure the angular distance (degrees) east or west of the Prime Meridian.
Expressed in degrees, minutes, and seconds
60 minutes in 1 degree
60 seconds in 1 minute
Lines of longitude run north - south
One degree of longitude ONLY EQUALS 69 miles, at the Equator.
Longitude lines do not stay the same distance apart. They are closer together near the poles than at the Equator.
Longitude of Mobile ≈ 88° 3’ W.
Latitude Longitude
Geographic
Grid or
GRATICULE
Graticule: the pattern of parallels and meridians on a globe
1. Parallels are straight east-west lines
2. Meridians are straight north-south lines
3. Parallels are equally spaced and never intersect one another
4. Meridians are farthest apart at the Equator and come together at the poles
5. Parallels and Meridians cross at right angles
Location of any place on earth can be expressed in latitude / longitude.
Examples:
Mobile, 30° 42‘ N, 88° 03‘ W
Sydney, Australia, 33° 55‘ S, 151° 17‘ E
Anchorage, Alaska, 61° 12‘ N, 149° 48‘ W
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What is the latitude/longitude of the exact opposite place on Earth to Sydney, Australia, 33° 55‘ S, 151° 17‘ E
90° N
LATITUDE
33° 55’ N
0°
Sydney
33° 55‘ S
90° S
Where is 34° N, 29° W ?
LONGITUDE
180°
Sydney
151° 17’ E
N P
West
29° W
0°
East
Sydney, Australia
34º S, 151° E
66.5°N
June Solstice
Summer in N. Hemisphere
23.5°N
Sunlight and darkness pattern on June Solstice
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December Solstice
Winter in N Hemisphere
23.5°S
66.5°S
Comparison of day and night at Anchorage,
Alaska, 61°N
(A) & Spokane,
Washington,
48°N (  ) on the
December
Solstice.
Sunlight and darkness pattern on Vernal Equinox
Spring and Fall Equinox
Equal day and night everywhere
March Equinox
June
Solstice
Sept. Equinox
You should know the names of these parallels, their latitudes, and where the vertical rays of the sun strike on the
June and
December solstices and on the March and
September
Equinoxes.
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0°S,   88°W
46°N,   116°W
21°S,   14°E
67°N,   51°W
Today’s classwork: on your map:
1. First figure out the degrees between each line, the map covers the entire world, and the distance between lines is the same in degrees.
2. Label the Equator and the Prime Meridian
3. Put the correct value on each latitude line
4. Put the correct value on each longitude line
5. Draw in the Tropic of Cancer, Tropic of Capricorn,
Arctic Circle, Antarctic Circle
6. Locate the following four places on your map
7. When you complete this, please help someone around you who is struggling with it.
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